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SQA Higher Computing Unit 2: Software Development

1. standard algorithms linear search counting occurrences and finding maximum minimum HERIOT WATT UNIVERSITY 8 1 INTRODUCTION TO MODULAR PROGRAMMING Revision Q1 A piece of programming code contains a validation routine This is to ensure a That the program produces the correct output b That the input data is within specified limits c That the output is within specified limits d That the input data is restricted to characters only Q2 Programming languages usually contain a collection of pre defined functions Which one of the following statements is true a Programming time can be saved b Functions produce a single value c Functions can be used with or without parameters d All of the above Q3 What is meant by the term standard algorithm Universal code to solve all problems A sequence of instructions that can be used to solve a common problem Code that makes a program more reliable a b c d Any program written in a high level language 8 1 Introduction to Modular programming This final topic introduces further modular programming concepts Programs are built up from individual blocks of code procedures and functions The main program will then consist of a series of procedure function calls which makes any program more readable and easier to maintain The fairly complex issue of parameters and parameter passing is covered in detail and exemplified by working solutions Fi
2. 4 6 2 Review Questions ET SUMMA a me e le MALE AS PS ae dE Sue Dee D D alae ee TE 4 8 End OftOpiC test ok amp amp ao hat eae we ele e BL AKA ow dt Prerequisite knowledge Before studying this topic you should be able to e describe the 7 stages of the software development process Learning Objectives e Identify the personnel at each stage of the Software Development Process e Understand the role of each person 50 51 51 52 53 54 55 56 57 57 58 59 59 49 50 4 1 TOPIC 4 PERSONNEL Introduction The Software Development Process involves many people throughout a computer system s lifecycle In this topic you will meet the personnel involved with a brief outline of their activities Although many people may be involved the key personnel are discussed under the five main headings a A WwW ND client project manager Systems analyst programmers independent testing group In a nutshell the process encompasses the following events 1 The company who require the new or updated system are the clients They approach external consultants the people who will create the system The consultants appoint a project manager who carries out a feasibility study If the feasibility study bodes well the management asks for a full system investigation This is carried out by a systems analyst from the consultants who works with the project manager It c
3. 137 6 16 1 Select Case Example 1 137 6 16 2 Select Case Example2 139 6 16 3 Select Case Example 3 141 6 16 4 Select Case Summary 142 617 SUMMANY gt Le me nn eos ie de une Bes ee S amp S aad 143 6 18 Endoftopictest 143 Prerequisite knowledge Before studying this topic you should be able to describe and use the following constructs in pseudocode and a suitable high level language input and output numeric and string variables assignment statements arithmetical operations logical operators AND OR NOT conditional loops using fixed and complex conditions IF statement nested loops Learning Objectives After completing this topic you should be able to e describe the need for programming variables e describe and use real integer string and boolean variables e describe string operations such as concatenation and substrings e distinguish between local and global variables understand what is meant by the scope of variables understand the nature and use of sub procedures e understand the use of selection in programming an in particular the CASE construct HERIOT WATT UNIVERSITY 6 1 INTRODUCTION 83 Revision 7 Q1 One of the following program statements produces the value 13 for the variable Answer Which one Answ
4. gt This program will prompt the user to enter a number gt and the day will be output Dim iDay As Integer iDay InputBox Please input a number between 1 and 7 Select Case iDay Case Is 1 PicDisplay Print iDay Case Is 2 PicDisplay Print iDay Case Is 3 PicDisplay Print iDay Case Is 4 PicDisplay Print iDay Case Is 5 PicDisplay Print iDay Case Is 6 PicDisplay Print iDay Case Else PicDisplay Print iDay End Select End Sub Private Sub Command2_Click End End Sub Sunday Monday Tuesday Wednesday Thursday Friday Saturday This file Case1 txt can be downloaded from the course web site Code 17 The program output is shown in Figure 6 17 HERIOT WATT UNIVERSITY 6 16 THE SELECT CASE STATEMENT 139 Form Figure 6 17 6 16 2 Select Case Example 2 Example 2 Using the Select Case statement with a range of values Problem Rewrite the previous If Then Elself program Code 16 using Select Case Statement Solution Here the keyword To is used to represent values within a range Use the following algorithm 1 ask user to input a mark between O and 100 2 select case mark case case case case case case O DO SF W 85 to 100 output Grade A 65 to 84 output Grade B 50 to 64 output Grade C 30 to 49 output Grade D O to 29 output Grade E else output mark outside range Try again end select T
5. 77 59 Translation methods 77 DO SUMMA Stea deca te cle ee ia ck E a ae a o doe DE CR 2e 80 BAT ENG OTTOPICTeSE 4 5 2 0a che mage feast A A ae ew wT 80 High Level Language Constructs 1 81 6 1 Introduction a ceo eee gl eee ache is wel ce aus Line a Boa ke eG GA 83 6 2 The Programming Environment 83 6 3 Building applications 26 2 264 00 pute EEA date Hole we eu 85 6 4 Program Structure le 8 ee Sls ds an Re dat Pas Sete Se wtih 94 6 5 Data typ s a wie ecw mans eb eh oe eas 97 6 6 Naming variables See we bee eee ee aw ue 204 98 6 7 Declaring Variables 4 428 808 dires VARS Se Las a 100 6 8 Declaring constants 103 6 9 Variables and scope 45m oka Teresa s er 109 6 10 Operators pren a Den mn ee m ee ee ER A de SD roue 112 6 11 Programming constructs 242 40 we n ga ph i a Eten 115 6 12 The lP Statement ia at e a Shee WS ae Ser ie Be ie 116 6 13 The If Then Else Statement 119 6 14 Comparison Operators eee ee BA Ae Se we ae 123 6 15 Other Forms of If Statement 130 6 16 The Select Case Statement 137 AF SURI ela sa ok Ae sear E Aer ek Sina teat and a Sat tocar th Ne os 143 6 18 End of topic test aa nine da Lane aie eB eae oe OGY Ride Cea 143 High Level Language Constructs 2 145 1 DR 11 10 0 UT 0 PRE ea eae Se ae ats 147 1525 FIMOGIOODS 2 USE Gis ie eat
6. Figure 6 8 1 If a variable is declared in the general declarations section with the Dim statement then it is Global to the entire program 2 If declared within the sub procedure then the variable becomes Local to that sub procedure and will not be recognised elsewhere Note VB also allows variables to be declared as Public or Private A Public variable is Global and can be accessed from anywhere in the project A Private variable can only be accessed from the form in which it was declared Consider the following program in Code 10 Option Explicit Program to demonstrate global and local variables Public TestVariable As Integer Dim TestString As String Private Sub ExecuteMain_Click TestVariable 55 TestString Hello 1 HERIOT WATT UNIVERSITY 110 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Print In main program Testvariable TestVariable Print In main program TestString TestString End Sub Private Sub ExecuteLocal_Click Dim TestVariable As Integer Dim TestString As String Print Print Call 1 gives TestVariable TestVariable Print Call 1 gives TestString TestString Print TestVariable 110 TestString Hello 2 Print Call 2 gives TestVariable TestVariable Print Call 2 gives TestString TestString End Sub This file Scope txt can be downloaded from the course web site Code 10 TestVariable and TestString are declared Public They are given values in sub procedure Execu
7. Its output will be e the user s d o b formatted correctly e the user s age These data items will be passes OUT of the procedure To produce these outputs it needs to know e the user s name e the user s d o b as supplied by the user These data items must be passed IN to this procedure We can add this to the structure diagram and the pseudocode GET USER FORMAT D O B DISPLAY INPUT amp CALCULATE OUTPUT AGE 1 get user input 2 do calculations IN name dob OUT dob age 3 display output IN name dob age HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS Finally think about the first procedure Get_user_input Its output will be e the user s d o b the user s name These data items will be passes OUT of the procedure It receives its input directly from the user when it is executed We can now complete the structure diagram and the pseudocode GET USER FORMAT D 0 B INPUT amp CALCULATE AGE DISPLAY OUTPUT 1 get user input OUT name dob 2 do calculations IN name dob OUT dob age 3 display output IN name dob age All of these data items listed above i e name d o b e age will need to be parameters HERIOT WATT UNIVERSITY 201 202 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS 8 2 1 3 byVal and byRef Visual BASIC like most other programming languages allows two types of parameter passing in VB these are called byVal
8. Num 1 Do While Num lt 10 Num Num 1 Loop MsgBox Num Although both loops end up with similar results their methods are different With the do until loop the condition Num 10 is set and the loop must be entered at least once to test this condition as true Num is continually tested until the condition fails i e Num becomes gt 10 and the loop exits with Num 10 The equivalent do while loop tests the condition in the first line and if false the loop will not be entered If true then the loop will run until Num 10 when the loop exits When should you use one and when the other If you know it is safe to run the code at least once probably you should use the do until loop If you must run the code at least once then again a do until loop is a good solution If there is any reason to doubt the value of any variables etc in the loop then you should HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS always use the do while loop Menus often use do until loops as you know that the menu needs to be run at least once for the user to see it A number of worked solutions to problems are given here make sure you understand what is going on in these examples You may wish to try running these programs for yourself and to experiment with making changes to the code to ensure you fully understand what is happening 7 6 7 Example 1 Guessing an age with do until and nested else If Problem A program is requir
9. TOPIC 4 PERSONNEL c Observation The analyst studies the current system and observes how it works This is useful for bringing to light things that users take for granted d Document analysis Many different kinds of document are involved in a system the documents that the system produces the documents it uses i e source documents and the documents that affect how the system works such as documents that spell out the procedures to be followed in using the system The first gives the analyst an idea of what the new system will have to produce and the second will help understanding of the workings of the current system e Expert Knowledge The analyst has to try to gain understanding of the processes the new system is supposed to help This understanding is important because particular people tend to take their own special knowledge for granted and as a result don t mention important requirements to the analyst A basic understanding of the process will allow the analyst to ask more searching questions during the interviews with key informants QUESTIONNAIRES lt lt OBSERVATION S mi E DOCUMENT o m m ANALYSIS i EXPERT SYSTEMS SYSTEM KNOWLEDGE ANALYST SPECIFICATION 4 4 2 Production of the problem specification Once the analyst has arrived at a clear idea of the problem this is expressed in a document called a specification It may be called the problem specification req
10. This program will illustrate the For Next loop using ve step Dim Counter As Integer Dim Char As String PicDisplay Print Spc 3 ASCII codes Spc 12 Character PicDisplay Print For Counter 90 To 65 Step 1 Char Chr Counter PicDisplay Print Spc 5 Counter Spc 15 Char Next Counter End Sub Code 21 Note that in this case the output has been formatted using the SPCO function This allocates a number of spaces between output items depending on the value expressed within the function HERIOT WATT UNIVERSITY 152 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 The program also uses the CHR function to convert a numerical value to its corresponding character For example Chr 65 returns the character A Part of the program output is shown in Figure 7 3 For Next 30 89 88 87 66 85 84 83 82 81 80 73 78 77 ZZOVODNHIC lt EX lt N Figure 7 3 ASCII code program 1 Code the program above 2 Adapt the program to display any range of ASCII codes and characters using Input Boxes to get the first and last number form the user HERIOT WATT UNIVERSITY 7 3 NESTED FOR LOOPS 153 7 3 Nested For loops For Next loops can be nested to allow the programming of loops within loops Consider the Visual BASIC program in Code 22 See if you can visualise what the output will be before looking at the results screen Option Explicit Private Sub Commandi_Click 16th February 2004
11. i 0 Do i i 1 Print i Loop Until i lt 5 2345 1 01 12345 Q16 What change can be made to the program fragment in the previous question to give the output 1 2 3 4 5 Change last statement to Loop Until NOTi lt 5 Change last statement to Loop Until i gt 5 Use a for loop with counter variable i a b c d Any one of the above 7 7 Formatting output Up to this point it has been left to Visual BASIC to output data in default mode However it is possible to have more control over how real values currency boolean variables are output by using the Visual BASIC in built function Format The structure of the Format function is Format variable format expression Table 7 1 shows the formatting functions within Visual BASIC Table 7 1 Format name Displays raw number without separators 12345 Fixed Displays at least one digit before the decimal point 67 88 and two digits after the point Uses scientific notation 6 023 E23 Standard Displays numbers with separators and two digits 1 234 56 after the decimal point Currency Same as standard Negative values are enclosed 1 234 56 within parentheses brackets Percent Displays numbers multiplied by 100 with two digits 12345 67 after the decimal point followed by the sign HERIOT WATT UNIVERSITY 7 8 ARRAYS 173 Exercise Output formats Write a Visual BASIC program to input real values and output the value in each of the
12. 4 Store it for future use 8 6 Further activities on Standard Algorithms Finding the maximum and minimum value in a list of integers Write a program that will find the maximum and minimum values in a list of integers Remember to construct appropriate test cases in advance of coding You should consider the following tests anormal test where maximum and minimum are as expected e atest where the maximum and minimum values are the same Sentence completion algorithms On the Web is a sentence completion task on algorithms You should now complete this task 8 7 Summary The following summary points are related to the learning objectives in the topic introduction modular program is very important in developing maintainable code modular program involves using procedures and functions to break up large blocks of code avoiding the use of global variables using parameter passing to pass data items between sub programs value parameters can only be passed IN to a procedure and the main program variable cannot be changed HERIOT WATT UNIVERSITY 8 8 END OF TOPIC TEST 227 e reference parameters are used where data must be passed OUT of a procedure the main program variable can be changed e user defined functions are an efficient and readable way of coding sub programs which return a single value e you should be able to write pseudocode and high level language code for the following standard algorithm
13. For example keyboard input should be checked and incorrect input rejected But this is not enough you need to give a message to the user to help them type the correct information next time If you do not do this you leave them floundering they know what they typed is wrong but have no idea why or what the correct input should be 1 3 Computing disasters It has been said Computers make very fast very accurate mistakes The software development process is important because without it you are bound to have a disaster in a project of any great size Large projects demand a large investment of money time and resources before any returns are possible Consider the following One in five software systems fail to deliver to the agreed specification e Software maintenance is the single highest computer related cost for many companies Some systems can take many years to develop running the risk of obsolescence before they are even commissioned HERIOT WATT UNIVERSITY 1 3 COMPUTING DISASTERS 1 3 1 Examples of Computing Disasters The list below contains a few examples of computing disasters that could be attributed to complexity and the need for better planning 1 Ariane 501 on the 4th June 1996 Ariane 501 exploded 40 seconds after takeoff due to a software bug This was an incidence of data conversion of a too large number 2 Y2K Problem The Millennium Bug problems with the way the date was stored on computers
14. G ecu used by the computer system a Design Implementation Working program Documents which fulfils the specification The code is written in a high level language such as Pascal C or Java and converted into code which the computer understands A high level language is one that people find relatively easy to understand The code written at this stage is called source code The machine can understand machine code a translation of the source code into binary instructions This code because it can be executed by a computer is also known as executable code The translation from source code into machine code is carried out by a program called a compiler The resultant machine code is portable to machines of the same type running under the same kind of operating system Compiling and debugging large programs can take a lot of time Another form of translation that can reduce development time is an interpreter When an error is encountered the interpreter immediately feeds back information on the type of error and stops interpreting the code This allows the programmer to see instantly the nature of the error and where it has occurred He or she can then make the necessary changes to the source code and have it re interpreted As the interpreter is also executing each line of code one at a time the programmer is able to see the results of the program immediately which can also help with debugging Sometimes problems that arise
15. If the condition is false to begin with then the do while loop will not be entered and control will pass to the rest of the program See Figure 7 6 test FALSE condition rest of program Figure 7 6 The do while loop is an example of a top tested while true structure The variant do loop while is an example of a bottom tested while true structure HERIOT WATT UNIVERSITY 160 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Do statements Loop while test condition The top tested loop can iterate between 0 and N times whereas the bottom tested loop may iterate between 1 and N This means that using the bottom tested loop the iteration must occur at least once so the condition can be tested immediately Care should be taken when writing programs using loops as an incorrect condition or mistakes in the body of the loop can cause the program to get stuck in an infinite loop when executing even when compilation produced no errors Should this occur in Visual BASIC simply click on program Run and choose End In more extreme cases pressing ctrl alt delete will allow you to abort Visual BASIC 7 6 2 Example 1 Calculating a sum of positive integers Problem A program is required to accept positive numbers from the keyboard calculate and display a sum of all the numbers entered It should use a do while loop which tests whether each number entered is greater than or equal to zero If the user enters a negative number
16. Loop Until end of list NO aA RF amp w D report minimum value Your result should resemble the images below Minimum 44 81 42 88 32 46 88 50 63 24 62 28 56 92 40 73 The minimum value in the list is 24 HERIOT WATT UNIVERSITY
17. Q4 One of the main reasons for the many programming languages existing is a older languages can no longer function in the present day computer systems b languages have to be adapted so new versions are released c there are many different types of operating system d people devise new languages because they do not like existing ones Q5 Which one of the following lists only contains general purpose programming languages a Pascal C BASIC COBOL b Algol Fortran Prolog Comal c BASIC Algol Pascal Comal d Fortran BASIC Comal COBOL Q6 In computer programming there are three basic constructs Which one of the following is NOT a programming construct a Sequence b Selection c Iteration d Moderation Q7 Which one of the following languages could be classified as being event driven HERIOT WATT UNIVERSITY 5 5 DECLARATIVE LANGUAGES 69 Q8 Which of these is not true of procedural languages They employ procedures and functions Programs written in the language are linear in structure Programming instructions are explicit a b c d They are low level languages Sentence completion languages On the Web is an interactivity You should now complete this task 5 5 Declarative languages Declarative languages model problem solutions very differently from procedural languages Programmers specify what the problem is rather than how to solve it In PROLOG for example a program represents
18. e A Bug and a Crash by James Gleick http www around com ariane html e Ariane 5 Learning from Flight 501 and Preparing for 502 European Space Agency ESA http esapub esrin esa it bulletin bullet89 dalma89 htm 2 Y2K Problem The Millennium Bug e What is the millennium bug http www wisegeek com what is the millennium bug htm 3 NASA Mars Lander e Metric mishap caused loss of NASA orbiter CNN http www cnn com TECH space 9909 30 mars metric 02 4 Passport fiasco http news bbc co uk 1 hi uk_politics 486821 stm 5 Asylum issue e http news bbc co uk 1 hi uk_politics 1171147 stm 6 Millennium bridge http www arup com MillenniumBridge Investigating computing disasters Several WWW sources of information about computing disasters have been given above Try to find out more about any two or more that might interest you Write a brief summary of two disasters that you have found HERIOT WATT UNIVERSITY 1 4 WELL PLANNED PROGRAMS 1 4 Well planned programs The most basic notion of well planned programs is to produce software that does what the user wants Other characteristics of well planned programs are 1 the software should be maintainable software with a long lifetime is likely to need changing This means that software must be written and documented in a way which makes change simple and straightforward 2 the software should be reliable and robust 3 the software should be effi
19. gt Program by Fred Fink This program will illustrate nested loops Dim Outer As Integer Inner As Integer For Outer 1 To 15 For Inner Outer To 15 PicDisplay Print Inner Next Inner PicDisplay Print Next Outer End Sub This file NestedlF2 txt can be downloaded from the course web site Code 22 In this program there are two loops that are controlled by the variables Outer and Inner For Outer For Inner Outer Loop Next Inner Inner Loop Next Outer The outer loop is initialised with the variable Outer 1 The inner nested loop is now executed 15 times and the first line of numbers are printed on the same line This is achieved by using the semi colon at the end of the first print statement Outer then takes on the value 2 and the process repeats itself until Outer 15 Each time the output is decreased by 1 as the outer loop is executed until the value 15 is reached HERIOT WATT UNIVERSITY 154 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 The print statement on its own ensures that a new line is taken for the next row of output The print statement on its own basically means a line feed The output of the program is shown in Figure 7 4 Note that it is considered bad programming practice to jump out of loops without terminating them fully After the loops terminate the counter variables are discarded so if this is aborted prematurely program output may not be as expected Nested loops SEN 10 11 12 13
20. 17 18 19 20 21 21 23 23 24 25 25 26 26 27 28 29 30 30 31 32 33 33 10 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS Prerequisite knowledge Before studying this topic you should be able to e describe the following stages of the software development process analysis design implementation testing documentation evaluation maintenance e describe and be able to use test data normal extreme and exceptional e describe the features of a user guide and a technical guide e evaluate software in terms of fitness for purpose user interface and readability Learning Objectives After studying this topic you should be able to understand the iterative nature of the software development process e describe each stage of the software development process e explain the purpose of the software specification and its status as a legal contract e understand and be able to describe corrective adaptive and perfective maintenance e explain the need for documentation at each stage of the software development process HERIOT WATT UNIVERSITY 2 1 INTRODUCTION 11 Revision 7 Q1 The software development process consists of seven stages Three of the stages are analysis testing and maintenance Which one of the following statements correctly identifies the missing stages in order a Design documentation evaluation implementation b Design evaluation documentation implementation c Design impleme
21. 3 NASA Mars Lander problems in software occurred when different measurement units were used there was confusion between pounds and kilograms 4 Home Office Immigration System Ordered in 1996 and supplied eighteen months late by Siemens in 1999 at a cost of 80 million It was supposed to speed the processing of asylum claims up but could not cope with the backlog and did the very opposite It was finally scrapped in 2001 Government ministers were blamed for ordering the over complex system in the first place 5 London Ambulance Service in 1992 they took on a despatch system that failed calamitously Ambulances were sent to the wrong place did not arrive when expected and the system generally caused major disruption to patient care and services 6 Passport Agency in 1999 anew system Siemens again that worked much less efficiently than the system it replaced Delays went up from two weeks to seven with a backlog of more than half a million passports This cost the taxpayers 12 million and forced many people to cancel holidays The Government increased passport charges to recoup wasted money from this system 7 Post Office swipecard system a one billion pound project that ICL were to install in throughout Britain It began in 1996 and was stopped in 1999 having been as the official report said blighted from the outset 8 French national library received a new system two years late and 40 over budget which worked so
22. FIXED LOOPS 149 4 the value of counter must not be changed in any statements within the body of the loop 5 changing the value of fina within the loop will have no effect on how many times the loop is executed 6 after the loop has terminated the value of counter is undefined 7 counter may be any ordinal type usually an integer initialise test condition FALSE increment rest of program Figure 7 1 The initial and final states may be constants variables or expressions e g for counter min 7 to max 5 The following examples will show the for next loop in operation 7 2 2 Example 1 Converting inches to centimetres Problem Write a program that will convert inches to centimetres for a range of values and using an increment of 5 Use the for loop and output the results in tabular form Use the conversion factor 2 54 centimetres to the inch Solution The algorithm is shown below display table titles for each value from 1 to 50 step 5 calculate conversion to centimetres using the factor 2 54 tabulate output next counter oa amp NN HERIOT WATT UNIVERSITY 150 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 The full Visual BASIC program is seen in Code 20 Option Explicit Private Sub Commandi_Click 16th February 2004 gt Program by Fred Fink gt This program will illustrate the For Next loop Dim Inches As Integer Dim Cms As Single PicDisplay Print Tab 3 Inc
23. The statement in the previous example Code 17 could be extended to give the following program Code 19 Option Explicit Private Sub Commandi_Click program use of case statement 3 16th February 2004 gt Program by Fred Fink To show the use of case with upper or lower case input Dim Day As String Dim FirstLetter As String Day InputBox Please enter the day FirstLetter Left Day 1 Pick off first character Select Case FirstLetter Case Mails mg PicDisplay Print Day is the weekend Case m M PicDisplay Print Day Case ts mp PicDisplay Print Day is a weekday is a weekday Case w W PicDisplay Print Day is a weekday Case f F PicDisplay Print Day is a weekday Case Else PicDisplay Print Day is not a day End Select End Sub Private Sub cmd_Exit_Click End End Sub This file Case3 txt can be downloaded from the course web site Code 19 HERIOT WATT UNIVERSITY 142 m 40 min TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Program output is shown in Figure 6 19 Form Figure 6 19 It is really important that you study this example carefully You will probably use the case statement a lot This program uses the case statement to check whether the letter typed in by the user matches s Saturday and Sunday m Monday t Tuesday and Thursday w Wednesday or f Friday If the match is with s it can only be a weekend All other matc
24. Use a nested loop to draw right angled triangle as shown below KKK kkkkk kkkkkkk kkkkkkkkk Pythagoras Theorem Write a program that will output integer values representing the sides of right angled triangles that satisfy Pythagoras s theorem i e a2 b72 c72 Only output values that satisfy the equation Hint You will require three nested for next loops and experiment with loop values up to 10 for each loop otherwise the program may run out of memory 7 5 Review Questions Q4 Which one of the following describes correctly an incremental for loop ied Control variable is decreasing in value by a variable amount Control loop variable is increasing in value by 1 Control loop variable is increasing by a variable amount Control loop variable is increasing in value by a constant amount determined by the programmer O D Q HERIOT WATT UNIVERSITY 157 30 min 30 min 40 min 158 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Q5 Which one of the following statements is not permitted For loopCounter For loopCounter For loopCounter For loopCounter 3 4 to 5 6 step 1 3 4 to 5 1 step 1 3 4 to 5 2 step 1 3 4 16 to 5 5 6 step 1 SON Q6 Which one of the following problems is best suited to the use of a FOR loop Calculating the total number of marks entered at a keyboard As an event loop that checks for keyboard input Calculating the average of marks held i
25. all numeric values become zero and strings become empty For this reason it is important that all variables are declared before a program is run To use a variable in Visual BASIC three quantities must be specified 1 Name of the variable 2 Type of variable 3 Value of the variable Variables are declared using the Dim statement which allocates temporary storage to them It is usual to use Dim statements before any other code so that total memory can be allocated at run time Examples of Dim statements are Dim Found As boolean Dim Maximum As integer Dim Precision As double Dim Myname As string 6 7 1 Implicit and Explicit declaration VB6 offers two levels of variable type declarations 1 Implicit declaration 2 Explicit declaration Implicit declaration to be avoided In implicit declaration if the dim statement is used on its own without assigning type to a variable or a variable is assigned a value then Visual BASIC will assign the data type variant This is the default setting that Visual BASIC will assign variables if not declared as some other type Visual BASIC does not force you to declare data types but it is much better if you do For example consider the following lines of code as shown Private Sub Form_Load HERIOT WATT UNIVERSITY 6 7 DECLARING VARIABLES 101 Dim MyText MyText Sample program FirstNumber 5 SecondNumber 10 Total FirstNumber SecondNumber End Sub
26. formats in Table 7 1 Use the algorithm below to help you Make the value large enough so that all aspects of the formatting can be shown The program should terminate when 0 is entered 1 Do 2 input a real number 3 display in general format 4 display in fixed format 5 display in scientific format 6 display in standard format 7 display in currency format 8 display in percent format 9 Until number 0 Run the program a few times with different values so that you understand the nature of each format Custom formats The Print Format allows you to create your own formats using various format characters 0 means display a zero or a digit means display a digit or nothing means multiply by 100 and insert a percentage character You can also add in any of the following characters For example Print Using 0 00 Tab 25 Format Number 0 00 See www vb6 us tutorials understanding vb format function custom numeric formats for more examples Adapt your program to experiment with this function 7 8 Arrays In the exercises so far you have looked at simple data types such as single real and integer The next thing we want to look at is how related data items can be stored together using arrays Much of this material may be familiar to you already However it is necessary to gain more practice in the use of arrays to prepare you for a later topic on standard algorithms which makes extensive
27. not just the keyboard A disk is an input device when the computer reads data including programs from it The program may also receive data internally during program execution The calculation is the heart of the program The input data is transformed to the output data This in short is all that a computer does The output phase is less straightforward There is no screen output in Visual BASIC only windows called forms Output can also be directed to a file printer or disc You will see example output methods in the program exemplars HERIOT WATT UNIVERSITY 95 96 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 6 4 1 Example program Suppose for example that you were going to write a program to calculate the area of a rectangle where the user will input the dimensions and the program will return the area The program will take the general form as shown in Code 6 Option Explicit Private Sub cmdDisplay_Click Dim Length As Integer Dim Width As Integer Dim Area As Integer Length Lngth Text Input length Width Wdth Text Input width Area Length Width Calculate area Ar Text Area Output result End Sub Code 6 This program uses text boxes to input and output the data 1 In the program the variables Length Width and Area are declared using the Dim statement see later 2 Values of Length and Width are input via text boxes 3 The area is calculated 4 Result output to a text box Figure
28. 14 15 11 12 13 14 15 11213 14 15 12 13 14 15 J DOS C2 FD 10 1112 13 14 15 11 12 13 14 15 12 13 14 15 13 14 15 14 15 15 Figure 7 4 Nested loop program Experiment with the loops and range of numbers to arrive at different outputs HERIOT WATT UNIVERSITY 7 3 NESTED FOR LOOPS 155 7 3 1 Use of an If statement with nested For Next loop Problem Write a program that calculates bank interest on a sum of money that is input by the user Output the capital sum together with the interest Solution Consider the following algorithm Ask user to input value If value lt gt 0 for count 1 to 10 calculate interest on value output value and interest next count else output message Value not valid try again end if oOo Non AUNE The Visual BASIC Code 23 is shown Option Explicit Private Sub Command1_Click 16th February 2004 gt Program by Fred Fink This program will illustrate nested loop and IF Dim Capital As Integer Counter As Integer Dim Interest As Single Capital InputBox Please input capital amount SumDisplay Print Capital If Capital lt gt 0 Then PicDisplay Print For Counter 1 To 10 Interest Capital Counter 100 PicDisplay Print Tab 5 amp Capital Tab 12 will gain amp amp Interest amp at amp Counter amp 4 Next Counter Else PicDisplay Print amp Capital amp is not a valid input Please try again End If E
29. 16 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS Questions to be asked at this stage would include e What are the new system requirements e What are the costs involved e How long will it take to implement Details are gathered by a variety of methods such as interviews and questionnaires 2 4 The Design Stage analysis The product of the analysis stage is the completed specification During the design stage the specification of the problem is used as the basis for a planned solution implementation testing documentation evaluation maintenance The work on the design is carried out by a Jf designer this might be same person as Lu xil did the analysis or it may be a member of A pee the programming team Most analysts can program and many programmers can carry out analysis People who can do both are Software Design stage Structure diagrams described as analyst programmers Specification pseudocode flowcharts data flow diagrams The design process is methodical using techniques such as structure charts and pseudo code The problem is approached by breaking it down into a collection of relatively small and simple tasks This approach is known as top down design with stepwise refinement The development team will attempt to make the design of the program both robust and reliable A reliabl
30. Beta testing Otherwise known as acceptance testing it takes place after alpha testing The idea is to subject a completed program to testing under actual working conditions If a program has been developed for use by particular clients it is installed on their site The clients use the program for a given period and then report back to the development team The process might be iterative with the development team making adjustments to the software When the clients regard the program s operation as acceptable the testing stage is complete If a program is being developed by a software house for sale to a market rather than an individual client the developers will provide an alpha tested version to a select group of expert users such as computer journalists and authors and also makers of related computing products such as printers This group is known as an independent test group Alternatively they may use professional software testers This is of benefit to both parties the software house gets its product tested by people who are good at noticing faults and the writers get to know about products in advance which further benefits both parties when the final production software is released the HERIOT WATT UNIVERSITY 25 26 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS software house getting publicity and the writers receive credit for being up to date People involved in beta testing will send back error reports to the d
31. Explic 6 8 Declaring constants 6 8 1 Example program 6 8 2 Example program itdeclaration Aie ested ne ace tae aN Re a de 1 Calculating the circumference of a circle 2 Use of a boolean variable 6 8 3 String variables and functions 6 8 4 Concatenation 6 9 Variables and scope 6 9 1 Review Questions 6 10 Operators 6 10 1 Operator precedence 6 11 Programming constructs 6 11 1 Sequence 6 11 2 Selection 6 11 3 Repetition 6 12 The IF Statement 6 13 The If Then Else Statement 6 14 Comparison Operators 6 14 1 Relational operators 6 14 2 Logical Operators 83 83 85 85 86 87 88 91 94 96 97 98 99 100 100 103 103 105 107 108 109 111 112 113 115 115 116 116 116 119 123 123 124 81 82 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 6 14 3 Logical AND qira aa BER eee er ee Be ee amp LA M 124 6 14 4 The Logical OR Inclusive 126 6 14 5 LogicaliNOT 224 3 6 4 rte mate A machin med EES 128 6 14 6 Review Questions 129 6 15 Other Forms of If Statement 130 6 15 1 Nested IF Statements optional 130 6 15 2 If Then Elself optional 132 6 16 The Select Case Statement
32. FirstNumber SecondNumber and Total have not been declared but Visual BASIC has assigned them data types on the fly the first time they encountered Although MyText has been declared it has no type All variables have therefore been assigned the type variant But beware If a variant variable is mis spelled later in the program then a new variable will be created by Visual BASIC This is a common error and can create program bugs that are difficult to find Explicit declaration to be encouraged In explicit declaration each variable is declared unambiguously using the Dim statement It is recommended that this option be used at all times This helps to prevent errors and allows the computer to work more efficiently If Visual BASIC knows the data type through declarations then the requisite amount of memory can be assigned thus making memory management more efficient Visual BASIC can be forced to make variable declaration the default setting By clicking on Tools then Options a window like Figure 6 4 will open Checking the Require Variable Declaration box will ensure Visual BASIC starts up in explicit declaration mode Note Visual BASIC NET does not support the type variant HERIOT WATT UNIVERSITY 102 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Options Editor Editor Format General Docking Enviranment Advanced Code Settings IV Auto Syntax Check IV Auto Indent Tab Width 4 V Auto Quick Info MV Auto Da
33. HIGH LEVEL LANGUAGE CONSTRUCTS 1 Events are actions which Visual BASIC detects and respond to For example e a user clicking on a command button on a form will generate a click event for that button pressing a key on the keyboard could initiate a load event for a programming module When an event occurs Visual BASIC will run any code that you have entered for that event The code for each event must be entered as a separate sub program Visual BASIC Environment When Visual BASIC is launched using the Standard EXE option a number of separate windows appear as seen in Figure 6 1 Note the layout of the windows on the screen may be different from the example shown they can be re arranged to suit your own preference a Project Microsoft isual Besic design File Edt Yiew Project Format Debug Run Query Diagram Took Addins Window Help D H Be eee 1 NPAs RAA Projecti a ols Bel Formi amp Forma Formi Figure 6 1 The default screen that you can see is in design mode and consists of four main windows 1 a blank Form window which is the interface with the application program you create The visual design of the program is created on this form which has gridlines to help build objects like text boxes labels and control buttons etc What HERIOT WATT UNIVERSITY 6 3 BUILDING APPLICATIONS is placed on a form will be displayed in a window when the program is executed 2 a Proje
34. In high level language code a variable declared outside a procedure is choose one a Local b Constant c Global d Functional Q10 Which one of the following describes the relationship between main memory and program variables a Name of variable identifies memory location b Data type defines how much memory is needed c Values of variables are held in main memory d All three statements above Q11 Which one of the following describes a local variable a Can be accessed anywhere in the program b They are hidden from other procedures and functions c Their values can easily be altered by mistake d The use of local variables is discouraged Q12 The scope of a variable is an important aspect in programming Scope is best described as a The range of values the variable can cope with b The amount of memory required by the variable c The extent to which the variable can be seen by the rest of the program HERIOT WATT UNIVERSITY 112 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 d The number of times the variable can be used in the program Q13 Which one of the following describes a boolean variable It holds a numerical value It cannot be used in expressions It is only used in looping structures It can have only the values true or false eus 6 10 Operators Assignment operator The assignment operator in Visual BASIC is the equals sign The general form for the assignment operator is varia
35. It helps the user to debug programs d An interpreter is ideal for beginners Q15 High level languages have to be translated because Computers can only understand machine code Source code is faster to run than object code Programs run faster when converted to binary All of the above 5 10 Summary The following summary points are related to the learning objectives in the topic introduction e there are many types of programming languages in use today including procedural declarative event driven and scripting they are difficult to organise into discrete categories because of overlapping properties high level languages have to be translated to machine code by compiler or interpreter scripting languages can be used to create and edit macros 5 11 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY Topic 6 High Level Language Constructs 1 Contents 6 1 Introduction 6 2 The Programming Environment 6 3 Building applications 6 3 1 Creating a form and objects 6 3 2 Attaching code to objects 6 3 3 Input and Output Controls 6 3 4 Input Methods 6 3 5 Output Methods 6 4 Program Structure 6 4 1 Example program 6 5 Datatypes 6 6 Naming variables 6 6 1 Review Questions 6 7 Declaring Variables 6 7 1 Implicit and
36. SUMMArYELEE LR Re Pee an eG Sept CARRE oh oe faye ter ee eb of Such Sete Set ENTO TOPICOS so rera bbe we Pee Se Seas ea ad ek Prerequisite knowledge Before studying this topic you should be able to describe and compare machine code and high level languages e explain the need for translation of high level language e describe the function of a compiler e describe the function of an interpreter e describe the process of recording a macro 63 63 64 66 68 69 70 72 73 73 75 75 76 77 77 77 78 79 80 80 80 61 62 TOPIC 5 LANGUAGES AND ENVIRONMENTS e assign a keystroke to a macro describe examples of the use of macros e describe the features of a text editor Learning Objectives After completing this topic you should be able to e understand the differences between procedural declarative and event driven languages e describe the uses of compilers and interpreters compare the functions and efficiencies of compilers and interpreters e describe the features and uses of scripting languages e describe how to create and edit a macro e describe the need for and benefits of scripting languages HERIOT WATT UNIVERSITY 5 1 INTRODUCTION 63 Revision 7 Q1 Programs are written in high level languages and then translated before they can be executed by a computer This is because a computers do not understand English words b itis easier to write high level code c computers o
37. Since a function returns a value it is used within expressions The function name must in the action part of the function be assigned the value that is to be returned A function is called using a statement of the form variable functionName parameters HERIOT WATT UNIVERSITY 8 3 FUNCTIONS 8 3 1 Pre defined functions Some built in Visual BASIC functions have been used in many of the programming examples up to now Table 8 1 shows some of the more common pre defined functions Table 8 1 ABS X Returns the absolute value of X ABS 5 6 5 INT X Returns truncated integer part of X INT 34 5 34 SQR X Returns the square root of X SQR 25 5 Generates a random number between 0 X 100 RND will give random numbers from 1 to 100 X Outputs at print position X Print TAB 5 SPC X Outputs number of spaces between last Print SPC 3 printed position and the next ASC X Returns the ASCII value of a character Print ASC A returns 65 my CHR X Returns an ASCII value into a character Print CHR 68 returns D VAL X Returns the value of string X VAL 76923 76923 STR X Returns the string of value X STR 1234 1234 8 3 2 User defined functions User defined functions work in exactly the same way as Visual BASIC a pre defined functions and extend the range of programming possibilities Here as a simple example is a little function that simply doubles the value sent to it function double n
38. Sub Add_10 ByRef Number As Integer Number Number 10 End Sub If they are now executed within a program we can see the difference to the variable Test in the main program by calling each procedure test test test add_10 add_10 byVal byRef The full Visual BASIC program is shown in Code 34 Option Explicit Private Sub Commandi_Click Dim Test As Integer Test 10 PicDispi Print Test Add_10 Test PicDisp2 Print Test End Sub Private Sub Add_10 ByVal Number As Integer Number Number 10 End Sub Code 34 HERIOT WATT UNIVERSITY 208 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Comparing byVal and byRef 1 Run the program as above 2 change byVal to byRef 3 Run the program again Compare the output Can you see why this is happening Your results should appear something like this Call by Value O Call by Reference Value of Test before call Value of Test before call Value of Test after call Value of Test after call Figure 8 2 Each procedure call produces the correct value of 20 for Test but only in call by reference is this value passed back to the main program In call by value the main program knows nothing about the local changes made within the procedure The process of events is as follows 1 The procedure call Change test is initiated 2 The procedure declaration Change is accessed 3 Procedure Change now accesses the memory location of variabl
39. and byRef byVal call by Value is used when a parameter is only an input to a sub program byRef call by Reference is used when a parameter is an output from a sub program Some parameters are both IN and OUT e g dob is both in and out for the do_calcualtions procedure In that case the parameter must be passed byRef Now we can complete the coding for the program showing these parameters e in the main program we declare all the parameters using Dim in the main program after each sub program call we list all the parameters used by that sub program whether in our out these are called the actual parameters after the header of each sub program we list its parameters again indicating for each one whether it is to be passed by value or by reference these are called the formal parameters Private Sub cmdAge_Click comment lines Dim name as String dob as String Dim age as Integer Call Get_user_input name dob Call Do_calculations name dob age Call Display_output name dob age End Sub Private Sub Get_user_input byRef name as String byRef dob as String Private Sub Do_calculations byRef name as String byRef dob as String byRef age as integer End Sub Private Sub Display_output byVal name as String byVal dob as String byVal age as integer End Sub Note it is important that the order of the actual parameters in the main program matches the order of the formal parameters in a sub_progr
40. are used Many organisations bring in consultants who design and carry out evaluations as the skills required to carry out effective evaluations are highly specialised The key criterion in evaluating a software product has to be whether it is fit for purpose i e does it meet the original specification and allow the client to carry out their tasks The evaluation is important for the user and the software author There are two reasons for conducting an evaluation e does the software meet the users requirements e how can the software house improve the product The performance of the system can be assessed in various ways e how closely does it fit the system design e how well does it meet the problem specification Questions may also be asked about matters such as e was the project within budget e was the project completed to schedule The development team will wish to review the project perhaps to learn from any mistakes to ensure they incorporate good points in future programmes Software houses aspire to produce new and better versions of their software They will study press reviews and note any contents and criticisms New or forthcoming changes in technology in operating environment and so on are also taken into account When the evaluation is complete work begins on the next version of the system For SQA assessment purposes you need to be able to evaluate software in terms of e robustness e reliability portab
41. badly that librarians walked out 9 ATMs in Germany during the changeover from Marks to Euros in 2002 a programming error in the banking system allowed people to withdraw any amount cash by typing in an arbitrary PIN code 10 London Millennium Bridge in 2000 the newly built Millennium Bridge wobbled when pedestrians attempted to walk over it In the computer simulation the programmers had used the wrong estimates for pedestrian forces HERIOT WATT UNIVERSITY 6 TOPIC 1 THE NEED FOR THE SOFTWARE DEVELOPMENT PROCESS Of course all these systems were A planned but with better planning these Good planning following Robust reliable software Satisfied clients mishaps might have been prevented pel poes Without planning probably all large projects would go wrong Poor planning ignoring the Poor unreliable software Unhappy clients SD process The most basic notion of well planned programs is producing software which does what the user wants This is easy to say but more than a little difficult to do If you are taking this course at the same time as learning a programming language then we are sure you know this is so from your own experience 1 3 2 Information sources on computing disasters The World Wide Web and Internet links go out of date rather quickly You might want to try accessing the following sites which are current at the beginning of 2004 1 Ariane 501
42. block is supposed to do its name should be a good indication of this What sort of program do you think is represented by the whole structure chart Formatted Output 3 2 4 Pseudocode Another method is to describe the design in terms of pseudocode Pseudocode is a non graphical design notation This is mostly used for working out the details of a design At this level pictures don t really help Pseudocode is a way of writing that lies somewhere between code and natural language such as English It represents an understanding of the solution that can be turned into code but can still be understood by people Pseudocode follows the indenting conventions of the programming language to be used for the project This indentation makes the pseudocode easier to follow and to understand HERIOT WATT UNIVERSITY 41 ee 42 TOPIC 3 TOOLS AND TECHNIQUES Pseudocode is a way of writing about a process without having to bother about details which are simply a matter of coding So that you could write convert entry to number without having to remember exactly how this is done in the chosen programming language Pseudocode frees us to get on with thinking about the details of program design without our having to stop and look things up in books or worry about whether we have got our syntax exactly right You use pseudocode to explain what a process will do in a clear and concise way One of the advantages of
43. cAvogadro As single 6 023E23 Const cName As string This is my name Some programmers like to express constants all in capital letters to differentiate them from variables This is an individual preference This makes no difference to the program whatsoever its only purpose is to bring to your attention the fact that this particular name is being used for a constant and not a variable 6 8 1 Example program 1 Calculating the circumference of a circle Problem Write a program that calculates the circumference of a circle when supplied with the radius The value of PI is defined as a constant Solution A typical solution to the problem is shown in Code 8 The circumference is calculated using the formula 2 x PI x r Note It is good programming practice to include internal commentary in every program The information makes the program more readable and also breaks the code listing into meaningful chunks HERIOT WATT UNIVERSITY 104 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 The comment symbol is the single quote Visual BASIC ignores all text that comes after the quote Comments can also be embedded within the lines of code Option Explicit Private Sub cmdCircle_Click program circle 10th February 2004 gt Program by Fred Fink gt This program prompts the user to enter a value for the radius of a circle It then uses the formula 2 PI radius to calculate the circumference Const PI As Single 3 14159 De
44. character is entered will the program fail to enter the loop and come up with the message Out of loop HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 163 This code can be used as part of a larger program to validate input If coded as a procedure then it can be called from within the main program We will discuss procedures more fully later in the final topic Input validation program Code run and test the program above 7 6 4 Example 3 Range checking using a boolean variable Problem A program is required to ask the user to enter a value If the value is outside the range expected the user will be prompted to enter another value This is another example of validation only in this program the use of a boolean variable is exemplified Solution The algorithm is shown below ON OO O1 AUNE 10 BPR Ree NN FE define upper and lower limits set value of ok to false Ask user to input a number do while ok false if number gt low value and number lt high value then set ok to true display This number is in range else display This number is out of range display Try entering another number input What number is needed end if loop display Out of loop The Visual BASIC program is shown in Code 26 Option Explicit Private Sub Commandi_Click program RangeCheck 18th February 2004 gt Program by Fred Fink This program prompts the user to enter numeric value It uses a WHI
45. circle Area Pi Radius 2 End Function Private Sub EndProgram_Click End End Sub This file FunctionArea txt can be downloaded from the course web site HERIOT WATT UNIVERSITY Fixed 8 4 REVIEWING FUNCTIONS AND PROCEDURES 215 Code 36 Turning a procedure into a function Any procedure that returns a single reference parameter cans be re written as a function Rewrite this procedure as a function It will return a valid integer It will no longer need a parameter sub getValidNumber ByRef number as integer Dim numberOK as Boolean do number Inputbox Input a number numberOK number gt 0 if not numberOK then Print The number must be greater than 0 end if loop until numberOK End sub 8 4 Reviewing Functions and Procedures Q13 Which one of the following statements regarding a function is true a A function does not need to be declared b A function cannot be defined by a user c A function returns a single value d Any procedure can be rewritten as a function Q14 Below are four functions Which one is not available as a predefined function in Visual BASIC a Inputbox b Val c Square d Rnd Q15 Look at the Visual BASIC statements below that use built in functions Which one represents a valid function call a SQR x x b y ABS 5 c 65 CHR A d z SQR z Function or Procedure ate You should now try the on line activity which tests your understanding of when
46. computer languages you have used Q1 When was it invented Q2 How many versions have there been since then Q3 What did it develop out of Classification of programming languages is fraught with problems since as you will see many languages can fall into more than one category Historically programming languages were classified according to whether they were ageneral purpose language that could be applied to a broad range of situations or a special purpose language that were designed for specific tasks Table 5 1 summarises some high level languages and variants HERIOT WATT UNIVERSITY 5 3 CLASSIFICATION OF HIGH LEVEL LANGUAGES Table 5 1 Historical classification of programming languages Pres Languagets General purpose ALGOL ALGOL 60 ALGOL 68 AL GOrthimic Language Scientific FORTRAN FORmula TRANslation Commercial COBOL COmmon Business Oriented Language Coding of general algorithms ALGOL 60 was the first defined language i e code produced identical results on any mainframe computer world wide Also introduced procedural programming and parameter passing Derivations are Pascal C C and COMAL Developed in the 1950s for use in scientific and engineering applications and is still in use today Suitable for data processing applications So widely used COBOL 2002 is the latest version in use Education Pascal Developed from ALGOL developed in the 1970s to teach structured p
47. conditions The software is therefore passed to other groups of people independent test groups who will undertake impartial testing Roles within Software Development On the Web is an interactivity You should now complete this task 4 6 1 Roles in classroom programming In real life programming all these roles are carried out by different people When it comes to the work you do in the classroom e the SQA or your teacher are the client you are the project manager systems analyst programming team and tester HERIOT WATT UNIVERSITY 58 TOPIC 4 PERSONNEL 4 6 2 Review Questions Q6 The program specification is an important document in the software development process The main reasons for this is a It can be used as a checklist to ensure the project is on target b Test data will be drawn up on the basis of this document c It describes all the inputs outputs and processes involved in the project d All of the above Q7 Which one of the following is not true of the programming team a They report directly to the project manager at all stages of programming b They are able to modify and repair existing programs c They are responsible for all test strategies concerning the software d They are overseen by the systems analyst at all stages of their work Q8 The completed project is usually tested by an independent group This is because a Independent test group will have better facilities for testing
48. different forms are linked HCI must be consistent so that similar actions in different parts of the interface have similar responses throughout the program Prompts given to the user should be consistent Different screens should look as though they belong to the same software package The HCI should provide on line help offering intelligible prompts and send messages and warnings to the user about the consequences of choices made e g send a warning if a user chooses to delete data HCI design is based on an appreciation of what the user wishes to see The designer thinks in terms of the windows often called forms that are presented to the user Identifying characteristics of a good user interface On the Web is a interactivity You should now complete this task 2 4 3 Designing Data Structures A program must perform operations on the data supplied to it The data should be structured data The choice of data structure will affect the entire program When the amount of data is likely to be very large the designer must consider the HERIOT WATT UNIVERSITY 2 4 THE DESIGN STAGE physical capacity of the hardware For example a million records of a thousand bytes each will require about a gigabyte If the clients want these records ordered in different ways in different parts of the program even a modern PC may have insufficient memory Many large systems involve a database In many cases the data is held in different ta
49. e ME tie ren ee 147 7 3 Nested FORIOODS s ats andre aire Beech ewe Bend Boe ee Se a res 153 fA Fixed Loop Exercises Si ane Re ation t dei domes ee Ree Ea 157 7 5 Review Questions amp culasse dlp BU an ea ee dd Sie wh ee ee 157 7 6 Conditional Loops tz 2 dep ise sus Bop enn Oo seh he mals oe 159 7 7 Formatting output amp oben oS GE Care OSG Pw ae dd 172 TB PRE AY IS Le te ie ee A ii RS RER NE AR er 173 PAS SUMMAY RE 2 Stag ch Tp tbe iis sg Ratti sw hs aes dy sarah AS Aa a ia 190 7 10 End OT topic test ss SL tea dns eo eae doe ek wwe ARE ss 190 Procedures Functions and Standard Algorithms 191 8 1 Introduction to Modular programming 193 8 2 Procedures and Functions 194 HERIOT WATT UNIVERSITY CONTENTS 8 3 8 4 8 5 8 6 8 7 8 8 PURCUOMS okie Shake Bist dE nn tes ae Hank ane ttes le Sa Aa Reviewing Functions and Procedures Standard Algorithms sx a6 SS eaatea ae amp pois us dew ee oy A ade Further activities on Standard Algorithms SUMMAN 248 amp Bee Stee a Fa ow E er hd Eye tee d et a i ef See A ENCOtOpictest 4 4 Laos ane Data et a gee ae ao ee eee amp 9 End of Unit Test Glossary Hints for activities Answers to questions and activities 2 ONO W Features of Software Development Process Tools and techniques Personnel ss ses aoa PR A See te hi dates Languages a
50. false depending on the value of the number entered Solution The algorithm is shown below 1 issue message to enter number 2 read the number typed in at the keyboard 3 set the boolean variable to true or false depending upon number gt or number lt 0 4 display result message The full Visual BASIC code for this program is shown in Code 9 Private Sub cmdRun_Click HERIOT WATT UNIVERSITY 106 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 10th February 2004 gt Program by Fred Fink Dim number As Integer Dim result As Boolean This is a program that will prompt the user for a number gt It will then check whether the number is less than or equal to zero or greater than 0 gt A boolean variable will hold the result A message saying gt true or false will be printed on the screen to say whether it is gt greater than zero Start of main program number InputBox Please enter a number result number gt 0 Print number greater than or equal to zero result End Sub Code 9 In this program the InputBox function is used to input the data as before The output is shown in Figure 6 7 Form 6 greater Ihan or equal ta zero True 1 greater Ihan or equal ta zero True 0 greater Ihan or equal ta zero True 1 greater Ihan or equal ta zero False 6 greater Ihan or equal ta zero False Figure 6 7 Boolean values are easy to use and when used they can often make a program mo
51. fo if the element in X is equal to the element in Y if the element in X is less than the element in Y Then print out a three column table displaying the contents of the arrays X Y and Z Make up your own test data and write down in three columns the number you input for X the number you input for Y and the result you got for Z HERIOT WATT UNIVERSITY 189 a 30 min 190 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 7 9 Summary The following summary points are related to the learning objectives in the topic introduction understand and be able to use the for next structure understand and be able to use the do while structure and variant understand and be able to use the do until structure and variant e how to declare 1 D arrays initialise a 1 D array manipulate data held in 1 D arrays 7 10 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY Topic 8 Procedures Functions and Standard Algorithms Contents 8 1 Introduction to Modular programming 8 2 Procedures and Functions 8 2 1 Procedures 8235 EUNCUONS 0558 naa LA NE de PAR oies Be a AS ete 8 3 1 Pre defined functions 8 3 2 User defined functions 8 3 3 User defined Function Examples 8 4 Reviewing Funct
52. gt Palarray length count Then isPalindrome False Else count count 1 End If Loop If isPalindrome Then PicDisplay Print is a palindrome Else PicDisplay Print is not a palindrome End If End Sub This file Palindrome txt can be downloaded from the course web site Code 31 Further notes on Section 2 Examine the do while statements carefully You will see that the conditions are compound e the character read in must not be a full stop AND there must still be space left in the array e if both these conditions are fulfilled then the loop continues if either one or the other condition fails then the loop terminates Further notes on Section 3 The do while isPalindrome and count lt length 2 statement tests whether you have gone halfway through the array AND whether the boolean variable isPalindrome has been set to false This needs a bit more explanation e notice that we initialised isPalindrome to true at the beginning of the program if you look at the output statements right at the bottom of the code you can see that if isPalindrome is still true then the array is a palindrome e if isPalindrome has been set to false at any point then the array is not a palindrome HERIOT WATT UNIVERSITY 7 8 ARRAYS this is what a boolean flag is for You set it to a state here it is either true or false and you use this value to see whether a certain condition still holds
53. knowledge as facts and rules Collectively facts and rules are called clauses A proposition is the smallest unit of knowledge that can be judged true or false such as a collie is a sheepdog or a beagle is a hound or George passed a ball to Steven In PROLOG these facts would be written as sheepdog collie fact that a collie is a sheepdog hound beagle fact that a beagle is a hound passed_a_ball george steven A rule contains a condition Cats purr if they are stroked by humans This would be expressed in PROLOG as purr X stroked_by X humans where X cats PROLOG facts and rules are stored as a database or knowledge base which can then be queried to provide solutions Example Using facts rules and queries Problem Suppose we want to find out whether a person drives a fast car We start by building a set of facts and rules for our knowledge base Solution person judy this is the fact that Judy is a person person james drives_car james ford_escort HERIOT WATT UNIVERSITY 70 TOPIC 5 LANGUAGES AND ENVIRONMENTS drives_car judy porsche this is the fact that Judy drives a Porsche drives_fast_car X drives_car X Y and Y porsche In this example we could ask the program to tell us whether Judy drives a fast car by typing the query drives_fast_car judy The result would be YES since the goal is satisfied If we asked drives_fast_car james then the result would be
54. line names and arrows describe the data that flow from one block to another andthe direction in which they flow Each block in the structure chart represents a section of code to be written These sections are called modules The modules in a structure chart will become modules of code in the finished program The designer must give the modules meaningful names rather than Block 1 Block 2 HERIOT WATT UNIVERSITY 3 2 DESIGN METHODOLOGIES AND NOTATIONS etc which describe what the module does This makes the design easier to follow The project as a whole is at the top A structure chart shows the relationship between modules and in particular shows which modules contain calls to modules lower down in the structure A complete structure chart of a large software system shows the relationship between all the modules in the system By convention structure charts are kept simple with no more than half a dozen blocks to each chart What matters is that the picture should be clear and easy to bear in mind If a block needs further refinement that can be represented in another chart Describing a structure chart PRODUCE BEST SOLUTION Good Input Nos Solution UE PUT OUT SOLUTION SOLUTION Solution Formatted Output FORMAT DISPLAY OUTPUT OUTPUT Figure 3 3 Sample structure chart Figure 3 3 shows a structure chart Make a list of all the modules and all the data flows Remember to make a sensible guess at what each
55. notations used to represent the design Design documentation will often include more than one notation e g structure charts for the higher levels to provide an overall picture and the pseudo code for the detail Often the design notations are used at different stages in the design process and serve to provide information to different audiences 3 2 1 Top down design with stepwise refinement Top down design with stepwise refinement is an approach used in computing and in many other fields as well The idea behind it is this 1 A problem might be difficult to solve as it stands so you try to break it down into a set of smaller problems which might be solved more easily This represents the first step of the process 2 You then take the smaller problems one at a time and break them down into still smaller problems 3 You keep repeating this process of breaking the problems down until all the problems facing you are small enough to handle At this point you are able to create detailed designs which can be turned into programming code The process is top down because you start with an overview of the whole problem and gradually work down to the fine detail It is called top down with stepwise refinement because the designer works through a series of steps gradually refining the small detailed aspects of the program One other advantage of this systematic approach is that it also automatically gives a structure to your solut
56. object and a newly created sub class This allows code re use by extending an existing class Intermediate code A form of compiled code that is specifically produced for a target computer Internal commentary The use of comments within source code to describe what it does Internal documentation The use of comments within source code to describe what it does Interpreter A program that translates a high level program line by line which it then tries to execute No independent object code is produced Iterative An iterative process is one that incorporates feedback and involves an element of repetition Jackson Structured Programming A diagrammatic design method for small programs that focuses on sequence selection and iteration Java A language designed by Sun Microsystems The language is portable because Java interpreters are available for a wide range of platforms Keyword A reserved word with a special meaning in a computer language For example for if dim in Visual BASIC HERIOT WATT UNIVERSITY GLOSSARY 235 Legal contract A contract set up between client and development team the details of which are set out in the requirements specification which becomes legally binding should anything go wrong Lexical analysis Part of the compilation process where the source code is tokenised into symbols and stored in the symbol table Linear search A standard algorithm that perform a sequential search on a list of data it
57. process requirements specification program design documents for the HCI and for the structure and logic of the underlying code a structured listing of the code and a test history HERIOT WATT UNIVERSITY 2 7 THE DOCUMENTATION STAGE 2 7 1 User guide The user guide contains information about how to install start and use software It should also contain a list of commands and how to use them Where there is a significant HCI the guide will show each form menu and icon and associated instructions about their use User guides may be supplied as paper manuals often with separate manuals for installation getting started and the user guide User manual Increasingly software vendors supply the manuals on disc or CD where they may be available in pdf or hypertext markup language HTML Paper manuals are costly to reproduce manufacturers frequently include electronic files which provide up to date amendments This lets the user read up to date information which could not be included in the original paper manual It is common for sample files to be included which complement the tutorial and provide the user with demonstration files The program should contain a help facility It is common for on line help to be presented in three tagged pages Contents Index and Search The contents present the help chapter by chapter the index refers to certain key words in the chapters and search offers the facility to locate key te
58. pseudocode is that it can be translated into programming language code fairly easily By writing out your program in this way you are opening up the possibility of re writing it in a large number of different forms suitable for different machines Many designers use a numbering system for parts of the design Each block in the structure chart has its identifying number and each line of pseudocode is also numbered These numbers enable parts of the program to be related and show their dependencies For example a block number 3 1 in a structure chart might indicate that this is the first sub module in the third module in the main part of the program A line of pseudocode 3 1 10 would indicate the tenth line in this module Here is an example of a standard algorithm that you will meet in your programming exercises written in numbered pseudocode HERIOT WATT UNIVERSITY 3 2 DESIGN METHODOLOGIES AND NOTATIONS 43 Counting occurrences set counter to zero prompt user to input search value set pointer to start of list do compare search value to item at current list position if search value current item then increment counter by 1 set pointer to next position in the list loop until end of list output number of occurrences counter Characteristics of pseudocode On the Web is a interactivity You should now complete this task 3 2 5 Review questions op PP PSP PWNS verher w N e Q4 Which of the following is a graphical design
59. site Code 27 The output is shown in Figure 7 10 Form Guess my age 60 is too high 16 is too low 45 is too high 18 is too low 31 is too high 23 is too highl 22 is too high OKk so its 21 but it toak you 8 tries Figure 7 10 Guess my Age program Code run and test the program above 7 6 8 Example 2 Fibonacci numbers Problem Write a program to output numbers belonging to the Fibonacci series up to a specified maximum Fibonacci was a famous Italian mathematician who identified the following series of numbers HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 169 Successive terms of the series are calculated by adding the previous two numbers Solution The following algorithm will produce the series given the first two values as input Do input number of terms to output loop until input is within range input two starting values do compute numbers display numbers loop until number of terms have been output ON O1 O1 amp UNBE Option Explicit Private Sub Commandi_Click program Fibonacci 17th February 2004 gt Program by Fred Fink gt This program will prompt the user to input the maximum value of terms to be displayed Two starting values are also input Dim NoOfTerms As Integer First As Integer Second As Integer Dim Third As Integer Count As Integer PicDisplay Cls PicDisplay2 Cls Do NoOfTerms InputBox How many terms to display Validation check Loop Until NoO
60. software b Programmers will tend to test only within the functionality of their own code c Independent test group will not test further than they have to so saving time d Programmers are happy to test their programs to destruction Q9 If a project begins to run over budget who is responsible for dealing with the problem a The client b The programming team c The systems analyst d The project manager Q10 In beta testing which one of the following is true Testing is done in house Testing is done by specialist personnel at cost Testing is done by external groups on a variety of computer platforms Testing focuses on the problem specification Online there is an interactivity Matching personnel to stages which you should attempt now HERIOT WATT UNIVERSITY 4 7 SUMMARY 59 4 7 Summary The following summary points are related to the learning objectives in the topic introduction many different people are involved in the software development process the client who may be an individual or an organisation is the buyer of the software being developed the users are the people who will actually use the software the project manager takes overall responsibility for the whole project the systems analyst clarifies what the client requires draws up a specification and produces a design the programming team implements this design and may carry out testing an independent test group may be used to carry ou
61. the next element in the list end if loop if not found then display message end if ON OO O1 AUNDE e e O Bee PW N The full Visual BASIC program is shown in Code 37 Examine it carefully to see how it operates based on the algorithm The output of this can be seen in Figure 8 5 Option Explicit Dim Found As Boolean Dim SearchKey As Integer Pointer As Integer Fill As Integer Dim List 15 As Variant Private Sub Command1_Click gt Program Linear_Search 29th February 2004 gt Program by Fred Fink gt This program will perform a linear search on an array holding 16 random integers between gt the values 1 and 99 Setup Call procedures Populate_List List Enter_search_item SearchKey Search_for_item Pointer SearchKey List End Sub Private Sub Setup Initialise variables Randomize gt and clear output boxes Found False HERIOT WATT UNIVERSITY 8 5 STANDARD ALGORITHMS 219 PicList Cls PicResult Cls PicResult Print Pointer 0 End Sub Private Sub Populate_List ByRef List Fill array with Dim Fill As Integer 216 random numbers For Fill 0 To 15 List Fill Int 99 Rnd 1 PicList Print List Fill Next Fill End Sub Private Sub Enter_search_item ByRef SearchKey User input search item SearchKey InputBox Input search key End Sub Private Sub Search_for_item ByVal Pointer ByVal SearchKey ByRef List Do While Pointer lt 15 And Not Found If L
62. then the loop will terminate and the total will be displayed on the screen Solution The algorithm is shown below set the running total to 0 display Give me your first number get number typed in at the keyboard do while user s number gt 0 add number to the running total display Give me the next number get input typed in at the keyboard loop display the total ONO O1 amp WN EB The Visual BASIC program is shown as Code 24 Option Explicit Private Sub Commandi_Click 17th February 2004 gt Program by Fred Fink gt This program will illustrate the Do While loop program addPos gt This program will add a list of positive numbers typed in at the keyboard The program will stop when a negative number gt is entered and display the total HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 161 Dim iNumber As Integer Total As Integer Total 0 iNumber InputBox Give me your first number Do While iNumber gt 0 Total Total iNumber iNumber InputBox Give me your Next number PicDisplay Print Your numbers add up to Total Loop End Sub This file DoWhile txt can be downloaded from the course web site Code 24 The program output is shown in Figure 7 7 Do While loop our numbers add up to 10 our numbers add up to 20 our numbers add up to 30 our numbers add up to 46 our numbers add up to 66 our numbers add up to 71 our numbers add up to 71 our numbers add up to 71 Fi
63. true so what might set isPalindrome to false It is the code inside the while do loop which compares the first and last items if they are not the same the boolean flag is set to false Otherwise nothing happens then the second and second from last are compared and so on In terms of loop tests this is probably about as complicated as it gets If you do not understand it this time around just be patient you will probably find that you need to code something like this yourself in the future and you can come back to this example By actually doing it the difficulties seem much less than by reading it as you are doing now Coding the Palindrome Checker Now code and test the palindrome checker You can save yourself time by copying and pasting the code into your VB editor once you have designed the interface and form Improved palindrome checker Adapt the previous program to ignore any spaces and any upper lower case differences Comparing arrays and encoding the results Declare three 20 element arrays X Y Z Write a program to read 20 integers into each of the two integer arrays X and Y The program will prompt the user to enter the values into each of the arrays The program will then compare each of the elements of X to the corresponding element in Y Then in the corresponding element of a third array Z store the following values Table 7 2 Table 7 2 Value if the element in X is larger than the element in Y
64. use of this type of data structure A data structure is a way of storing data in a computer in an organised way One of the simplest data structures used in computer programming is called an array and is an example of a static data structure because it is of a fixed size within memory as defined within the structure of the program HERIOT WATT UNIVERSITY 174 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 An array is a list of data items where each item is uniquely identified by its position in the list An array is given a name which is usually related to the group of data it holds Some examples might be Sunday Monday Tuesday Wednesday Thursday Friday Days of the week Saturday 0 1 2 3 4 5 6 7 8 9 A B C D E F Hexadecimal digits 1 2 50p 20p 10p 5p 2p 1p Decimal coinage 7 8 1 1 D Arrays The data items in 1 D arrays are simply stored in consecutive locations within a block of computer memory as follows O Sunday Days of the week 0 1 Days of the week 1 2 Tuesday f Days of the week 2 Index Values gt 3 Days of the week 3 4 Thursday jf Days of the week 4 5 Days of the week 5 6 Saturday f Days of the week 6 Thus the data item Tuesday is stored in array location Days_of_the_week 2 and the data item Saturday as Days_of_the_week 6 Each data item therefore is uniquely identified by its index Note that the index values are not actu
65. use them to enable decisions to be made in programs the if statement e use of logical operators in decision making e the if else statement e nested if statements multi way branching with elseif e the case statement 6 11 3 Repetition Repetition control structures are covered in the next topic following a look at the details of selection control structures 6 12 The IF Statement The general decision making capability in Visual BASIC is provided by the if statement The format of this statement is if condition then statement or if condition then statements end if HERIOT WATT UNIVERSITY 6 12 THE IF STATEMENT 117 if expression FALSE TRUE rest of program The program statement may be a single statement or may be a block of statements When the expression is true the statements following are executed When the expression is false then none of the statements are executed and control passes to the remainder of the program Example 1 Using a simple IF statement Problem A program is required to ask the user for a number If the number entered by the user has the same value as a value stored in a constant then the program will display a suitable response The algorithm is shown below Solution request a number from the user get number typed in at the keyboard IF the number typed in the program constant THEN display I like 99s display Program End So you don t l
66. with or without parameters Q9 The structure of a procedure consists of three main parts Which one of the following is not one of these parts A heading A declaration An action A footer a0 0 9 HERIOT WATT UNIVERSITY 212 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Q10 Parameters can be classified as being IN OUT and IN OUT Which one of the following statements is true regarding these parameters a byVal is used for IN OUT parameters b byRef is used for IN OUT parameters c byRef can only be used for IN parameters d byVal can only be used for OUT parameters Q11 In a procedure where a parameter is called by reference which one of the following is true a A reference parameter is an example of an IN parameter b Anything that happens to the formal parameter happens to the actual parameter c The parameter must be an Integer variable d Only one parameter can be called by reference Q12 What would be the output of the following Visual BASIC code Dim x As Integer y As Integer x 5y 6 Print x y result x y Print x y Sub result ByRef numi As Integer ByVal num2 As Integer numi numi 10 num2 num2 3 End Sub 8 3 Functions A function is similar to a procedure except it returns a single value to the calling code The basic structure for a function is Function functionName parameters As Data Type Declarations functionName expression End Function
67. worries 6 15 2 If Then Elself optional Nested if statements can be fairly complex to follow and can give rise to what is known as spaghetti code It is usually better to use Select Case as described in Section 6 16 The ElseIf statement can simplify expressions to a certain extent The structure of the statement is if expressioni then statements 1 elseif expression2 then statements 2 elseif expression3 then statements 3 else statements 4 These expressions are evaluated in order if any expression is true the statement associated with it is executed and this terminates the whole chain As many decisions as desired may be included within the chain As always the code for each statement is either a single statement or a group of statements Consider the situation where you have two boolean variables booly1 and booly2 and you need to take actions for each of the possible combinations of true and false Using nested if statements would produce If boolyi True Then If booly2 true Then HERIOT WATT UNIVERSITY 6 15 OTHER FORMS OF IF STATEMENT 133 statements for true true Else statements for true false End If Else If booly2 false Then statements for false true Else statements for false false End If End If Using ElseIF will produce the following more compact code If booly1 And booly2 Then statements for true true ElseIf booly1 And Not booly2 Then statements for true false ElseIf Not b
68. 2 Standard algorithms and module libraries Standard algorithms Most projects will use certain standard algorithms Programmers need to be familiar with these common algorithms Ones that you will become familiar with later include e linear searching counting occurrences e finding maxima and minima Module libraries It is often possible to use with or without alteration modules that have been previously written and have been retained in a module library A module library will include code for standard algorithms Most development environments come with a large library of modules Programmers can use these in the code they are developing These libraries will include mathematical functions modules for converting text to numbers etc HERIOT WATT UNIVERSITY 21 22 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS if eval _root drag1 _droptarget _root target1 _root drag1 _visible false _root target1 nextFrame _root target1 _name false __parent answer _parent answer 1 if _parent answer 12 _Pparent message01 Well done Each module in a module library is pre tested well documented so that it can be adapted and easily used The use of previously written modules reduces the time spent creating the final software and minimises the cost Designers will incorporate if possible modules from the module library in the design For many software companies and programmi
69. 440 minutes in a day Hint 3 For example days 1 hours 12 minutes 15 Total number of minutes 2175 days 3 hours 4 mins 5 total minutes 4565 days 17 hours 10 mins 0 total mins 25080 Calculating the number of digits in a number Hint 1 It helps the user to know what type of number to type in and what range of numbers is allowable before they type the wrong input This should be in addition to any checks you do on the length of the number Calculating Leap Years Hint 1 shows several years and indicates whether they are leap years or not This data could be used to test your program Table 9 1 HERIOT WATT UNIVERSITY 242 HINTS Table 9 1 Calculation of leap years Is a Leap Year 1900 Yes Yes HERIOT WATT UNIVERSITY ANSWERS TOPIC 2 243 Answers to questions and activities 2 Features of Software Development Process Revision page 11 Q1 c Design implementation documentation evaluation Q2 d User and Technical Guides Q3 a Program listing Answers from page 13 Q4 d Analysis design testing evaluation Q5 a The team may go back to an earlier stage to deal with a problem Q6 dj All of the above Q7 b Enable personnel to discuss progress Answers from page 17 Q8 a top down design Q9 d software specification Q10 d All of the above Q11 b Robust Q12 a a description of what the software must do Answers from page 23 Q13 c It
70. 6 hold the days of the week The 4th array element is assigned the value Wednesday The correct statement for this is a Days 4 Wednesday b Days 3 Wednesday c Days 4 Wednesday d Days 3 Wednesday Q3 An array called List 5 contains the integers 1 to 6 in sequence If the 2nd and 4th elements are now assigned the values 8 and 9 respectively the array List will now contain OO VONN w w AORO anon OOO ee 22 7 1 Introduction An important aspect of this topic is the 1 dimensional array Declaring and initialising arrays are introduced together with how data is manipulated within arrays using various looping structures Each sub topic has working solutions to the example programs providing a suitable environment for building confidence in writing programs before the final topic dealing with standard algorithms is covered 7 2 Fixed loops The aim of this topic is to consolidate your knowledge of iterative structures or loops Iteration simply means repetition which in the context of programming is the execution of blocks of code many times over Iteration is a fundamental part of almost every program and is one of the most useful features of programming You do not want a computer to produce one payslip but many payslips to add up just two numbers but thousands of numbers to put in order just two items but thousands of items HERIOT WATT UNIVERSITY 147 148 TOPIC 7 HIGH LEVEL LAN
71. 6 3 shows a program run HERIOT WATT UNIVERSITY 6 5 DATA TYPES Form Input Length Input Width Area of rectangle is Figure 6 3 You can see that the form contains 3 labels and 3 text boxes for the input and output of data and a control button 6 5 Data types Visual BASIC has a number of in built data types the significant ones for this topic being integer single real boolean and string These are summarised with others in Table 6 2 Table 6 2 Integer These are whole numbers positive or negative without a decimal point The range depends on the machine but if 16 bits long the range is 32 768 to 32 767 Long integer Extended range of integer from 2 147 483 648 to 2 147 483 647 Single real These are floating point numbers e g 3 33333 When 32 bits long their range is 38 and referred to as single precision Double real Double precision floating point numbers within the range 4 308 characters This data type can represent two values true and false variant Any numeric value up to the range of a double precision number or any character text HERIOT WATT UNIVERSITY 97 98 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Note that 1 Although the range of floating point numbers is huge they are not all that accurate often not much more than 8 16 digits depends on the machine and compiler The rest of the number you may see on the screen is an appr
72. A Managed software feverishly coding programmers development team Organisations creating software usually do so for profit Money time and people are involved The people involved have different points of view some are clients wanting to buy software some are developers concerned in creating software managers are concerned with efficiency and profit within their organisation In the development of software the three aspects which the developer must consider are e data processes human computer interface In traditional structured design the primary tasks are to focus on the processes A process is the work that a program carries out on data or in response to certain inputs The software development process does not always start in the same place Sometimes there will only be an outline of the problem At other times a specification will be available The specification must be agreed with the clients Work on the problem and the solution is often carried out by a group of people called the development team The aim of the team is to produce a new software system that will solve the problem 2 2 The need for iteration The traditional software development process contains a sequence of stages The precise names of the stages and even the number of stages are not universally agreed They differ from book to book and from developer to developer Much depends on the aspects of software development that a book wis
73. ECHNIQUES 3 2 2 Structure charts diagrams An important approach in practically all methods of analysis is to draw a picture of some kind Analysts use diagrams which show e the main elements of the solution e how they fit together It is not enough for the analyst to have a design in mind It must be represented in a form that can be used by all members of the team One method is to use structure charts which are sometimes called structure diagrams A structure chart gives a picture of the design A structure chart is an example of a graphical design notation Styles vary in detail but in essence structure charts consist of boxes lines arrows and text A box represents a block of code and has a name Usually it is a descriptive expression starting with a verb it shows the block s purpose Structure charts can be drawn according to various sets of guidelines These are the basic graphical elements TT Module Module call O Data flow argument A structure chart for a program that simply gets in some data changes it in some way and produces output might look like Figure 3 2 Control Figure 3 2 Software Design Structure 3 2 3 Interpreting Structure Charts Structure charts are read from top to bottom and left to right at each level The line joining two boxes indicates that the lower is called or brought into action by the upper The lower box represents one of the things the upper box has to do Along each
74. GUAGE CONSTRUCTS 2 There are three different looping constructs you can use in Visual BASIC 1 For Next loop 2 Do While loop 3 Do Until loop Most loops have the following characteristics in common e initialisation e a condition which evaluates either to TRUE or FALSE e a counter that increments or decrements by discrete values For Next loops are examples of fixed loops and we will study them first DO loops are conditional loops and we will study them later 7 2 1 The For Next loop When incrementing the general form of the For Next loop is For counter initial value To final value Step value statements Next counter When decrementing the general form is For counter initial value To final value Step ve value statements Next counter Note 1 The initialisation statement is carried out only once when the loop is first entered i e initialise counter to initial value 2 The condition is tested before each run through the body of the loop The first test is immediately after initialisation so if the test fails the statements in the body are not run An incrementing loop terminates when counter gt final while a decrementing loop terminates when counter lt final 3 An increment or decrement of the counter variable is executed after the loop body and before the next test The value of the counter is incremented or decremented by the step value HERIOT WATT UNIVERSITY 7 2
75. IOT WATT UNIVERSITY 126 i Oo 20 min TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Program output is seen in Figure 6 13 Form Both words Daffodil are identical affodil and Tulip ae not identical affodil and daffodi are net identical End Program Figure 6 13 Notice from the third entry that the input is case sensitive This could be resolved using the UCase or LCase pre defined functions Using the logical AND operator in an if statement Construct an if statement that displays a message if both the variables number1 and number2 are greater than 10 Validating numeric input and program testing Use fragments of code you have just seen in this section to help you write a program which will accept a value from the keyboard and print yes if it is positive and even Test your program with positive and negative numbers odd and even numbers and make sure it passes all the tests Make a tabulated list of the numbers you use and the results the program gives for each input Use both positive and negative numbers not neglecting zero 6 14 4 The Logical OR Inclusive If either the expression before the OR or after the OR is true then the whole expression is true This also means that if both the expressions are true the OR expression will evaluate to true So or means either one or the other or both Hence the term inclusive Use of the logical OR operator is shown below if Vone 6 or Vtwo 6 th
76. LE loop to repeatedly check that a value which is between LowValue and HighValue Const LowValue As Integer 10 Const HighValue As Integer 20 Dim size As Integer Dim OK As Boolean HERIOT WATT UNIVERSITY 164 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 OK False size InputBox Enter a number Do While Not OK If number gt LowValue And number lt HighValue Then OK True Print number Else Print number is out of range try again size InputBox What number is required End If Loop Print Out of loop End Sub This file RangeCheck txt can be downloaded from the course web site Code 26 is in range Sample program output is seen in Figure 7 8 Do while 15 is in range Out of loop 5 is out of range try again 25 is out of range try again 0 is out of range try again 10 is in range Out of loop 20 is in range Out of loop Figure 7 8 Range check program Code run and test the program above HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 7 6 5 Do While Review Questions Q9 What is wrong with the following n 0 assume n is an integer do while n lt 100 value n n loop Q10 What is wrong with the following i 1 assume i is an integer do while i lt 10 Print i i iti Q11 Write a while loop that calculates the sum of all numbers between 0 and 20 inclusive Hint use two integer variables one for a loop counter and one for keeping a running to
77. Main Program gt Program by Fred Fink 25th February 2004 This program exemplifies the use of value parameters HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 205 Dim ActualValue As Integer Do ActualValue InputBox Input a value between 1 and 100 Loop Until ActualValue gt 1 And ActualValue lt 100 Call Square ActualValue Call procedure PicDisplay Print Call SqrRoot ActualValue Call procedure End Sub Private Sub SqrRoot ByVal number As Integer Procedure declaration Dim Result As Single Result Sqr number PicDisplay Print The square root of number is Format Result Fixed End Sub Private Sub Square ByVal number As Integer Procedure declaration Dim Result As Integer Result number 2 PicDisplay Print The square of number is Result End Sub Private Sub Command2_Click End End Sub This file ValueParameter txt can be downloaded from the course web site Code 33 Squares and square roots with procedures Examine this code carefully Make sure you understand its structure The fixed format command is to output the square root to two decimal places Program output is shown in Figure 8 1 HERIOT WATT UNIVERSITY 206 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS The square of 58 is 3364 The square root of 58 is 7 62 End Program Figure 8 1 Note that the original value of the variable ActualValue in the main program remains unchanged A
78. Me re 2 10 Weaknesses of the software development process 2 11 Summary 2 12 End Of topie test iets Se en Ee ae Sy ee ee ae Tools and techniques Introduction Design methodologies and notations Test Data Structured LISting Lasers Se ena ath Nr Name re Error Reporting ea sh Ae oe a a AN os ee a a we dr re Summary End oftopic tests s La Lie td M A a aye nt dent ee Lie Personnel Introduction 44444 The Client The Project Manager as er SS ant ae je map den nai md The Systems Analyst e kya he af a ae ee ee ee a a Th Programming Teams 23404 ae fle oe She eA es date Les Independent Test Group Summary Con WP 11 12 14 16 20 23 26 29 31 32 33 33 35 37 38 44 45 46 47 47 49 90 51 51 52 56 57 59 CONTENTS 4 8 Endoftopictest 59 Languages and Environments 61 Bel 1ntodu tion us a mt pi ns dat Sey As aaa ak aa BA 63 5 2 Programming Languages 4 44 ese See be eee a ee ee 63 5 8 Classification of High Level Languages 64 5 4 Procedural Imperative languages 66 5 5 Declarative languages 24 2 der eines ans RE We 69 5 6 Event driven programs 52 Re Gade geek wale AE AUS RSA et 70 5 7 Scripting languages 2 2 seats Ale ne sun ds Diet be 72 5 8 Other Language Types
79. NO as drives_car james Y would evaluate Y ford escort This would then cause the rule drives_fast_car james to fail as Y does not equal porsche and the goal is not satisfied You can see from the code that there is no description of the type of data or its internal representation There are simply statements of facts and a rule Contrast this with a procedural language where the programmer would need to set up a structure to hold the knowledge and predefine its type string number etc Then they would need to describe the steps taken to search the structure in order to answer the query A declarative logical language is simplistically described as telling the computer what to do and not how to do it Goals and clauses On the Web is an interactivity You should now complete this task 5 6 Event driven programs Event driven programming languages have evolved to handle events Strictly speaking we should talk about event driven programs not languages Some languages such as Visual BASIC are ideal for creating event driven programs but it is the programs that are event driven not the language Events can be initiated at two levels 1 at system hardware level events can include timers interrupts loading of files etc 2 at language system level events include mouse clicks keyboard presses and cursor movements In Visual BASIC each object has a set of events associated with it An event is an action that Visual BA
80. OPIC 5 LANGUAGES AND ENVIRONMENTS it would perform those tasks The Macro is stored as a script using the application s scripting language VBScript For programs that don t include a macro facility there are numerous shareware macro programs that can be downloaded and used in any application 5 7 5 Running A Macro A macro can be initiated by pressing selected key combination hot keys e clicking an icon on the toolbar that has been created for the macro running the macro from the Tools menu of the application Example tasks could include inserting your name and address on documents formatting text with specified font and size accessing websites from a list of favourites inserting special symbols or graphics into documents automate playing of audio CDs while you work on the computer formatting of spreadsheet cells creating headers and footers Code 4 is an example VBScript listing for a macro to create a table in Microsoft Word Macro to create a table in Word 2 Sub Macroi 2 gt Macroi Macro Macro recorded 05 01 2004 by John Smith 2 ActiveDocument Tables Add Range Selection Range NumRows 7 NumColumns _ 4 DefaultTableBehavior wdWord9TableBehavior AutoFitBehavior _ wdAutoFitWindow With Selection Tables 1 If Style lt gt Table Grid Then Style Table Grid End If ApplyStyleHeadingRows True ApplyStyleLastRow True HERIOT WATT UNIVERSITY 5 8 OTHER LANGUAGE TY
81. PES 77 ApplyStyleFirstColumn True ApplyStyleLastColumn True End With End Sub Code 4 5 7 6 Review Questions Q9 An event driven language differs from other languages in that choose one a Programs have no pre defined pathway b Programs are initiated entirely from mouse clicks c Program events cannot be nested d Programs are difficult to write Q10 Which of these is not a benefit of scripting languages a They are easy to learn and use b Allow complex tasks to be performed in relatively few steps c Web pages can be made more dynamic d They describe a problem rather than how to solve it Q11 Many software applications include a macro facility Which one of the options best describes a macro a Macros are not easy to edit b The creation of a macro can be time consuming c Macros automate repetitive tasks d Amacro listing consists of complex code Q12 One of the tasks that a macro could NOT perform would be Inserting special symbols or graphics into documents Formatting a floppy disc Creating headers and footers a b c d Changing audio CDs 5 8 Other Language Types Other important language types include object oriented languages and functional languages You do not need to know about these for Higher Computing 5 9 Translation methods At the end of the implementation stage if all is going well a structured program listing will be produced complete with internal documentati
82. Rapid Application Development An alternative software development model that uses event driven languages for its implementation Recursion A programming technique that is iterative in that a procedure or function can call itself It is very demanding of computer memory Reference parameter Here the address of the actual parameter is accessed by the formal parameter Information is passed OUT from the procedure to the main program Reliable A program is reliable if it runs well and is never brought to a halt by a design flaw Repetition A process that repeats itself a finite number of times or until a certain condition is met Requirements specification A document describing what the system must be able to do in order to meet user requirements Robust A program is robust if it can cope with problems that come from outside and are not of its own making Scripting language Used for writing small programs or scripts that enhances existing software The best example is JavaScript which is used to enhance web pages Search key The data item being searched for by a search algorithm Semantics Semantics is the meaning of a statement in a given language Simulation Replication of a process by computer that would not be possible to do manually For example studying the projected traffic analysis of an airport or throwing a die many hundreds of times Software development environment The high level language programming environment that off
83. SCHOLAR Study Guide SQA Higher Computing Unit 2 Software Development David Bethune Andy Cochrane Tom Kelly lan King Richard Scott Heriot Watt University Edinburgh EH14 4AS United Kingdom First published 2004 by Heriot Watt University This edition published in 2011 by Heriot Watt University SCHOLAR Copyright 2011 Heriot Watt University Members of the SCHOLAR Forum may reproduce this publication in whole or in part for educational purposes within their establishment providing that no profit accrues at any stage Any other use of the materials is governed by the general copyright statement that follows All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means without written permission from the publisher Heriot Watt University accepts no responsibility or liability whatsoever with regard to the information contained in this study guide Distributed by Heriot Watt University SCHOLAR Study Guide Unit 2 Higher Computing 1 Higher Computing ISBN 978 1 906686 60 4 Printed and bound in Great Britain by Graphic and Printing Services Heriot Watt University Edinburgh Acknowledgements Thanks are due to the members of Heriot Watt University s SCHOLAR team who planned and created these materials and to the many colleagues who reviewed the content We would like to acknowledge the assistance of the education authorities colleges teache
84. SIC can detect and respond to A user clicking on a command button is an example of an event The programmer codes the actions that he she wants to happen when an event occurs HERIOT WATT UNIVERSITY 5 6 EVENT DRIVEN PROGRAMS 71 The following examples show the action of clicking on two buttons in a Visual BASIC program Button1 Display Message produces a message in the label window w nimi Pressing the clear button removes the message A typical event driven program has the effective structure do forever if event then if event caused by X then handle X else if event caused by Y then handle Y After each event is handled nothing happens until the next event occurs Note that event driven programs do not have a predefined pathway in the execution of the code as opposed to imperative programming style i e they have no fixed beginning or end Graphical user interface programs are typically programmed in an event driven style using languages such as Visual BASIC and Visual C HERIOT WATT UNIVERSITY 72 TOPIC 5 LANGUAGES AND ENVIRONMENTS Other languages such as Java an object oriented language can also be used to create event driven Windows style programs Event driven Programming On the Web is an interactivity You should now complete this task 5 7 Scripting languages A Scripting language is a style of programming that produces ASCII text based scripts which are usually
85. Sub This file Occurrences txt can be downloaded from the course web site HERIOT WATT UNIVERSITY 8 5 STANDARD ALGORITHMS 223 In this case the array is filled with values from 1 to 49 in order to increase the chances of multiple occurrences The output of this can be seen in Figure 8 6 Counting Occurrences 18 22 13 6 13 32 13 25 12 25 24 31 29 25 25 34 ica item 25 found 4 times in the list End Program Figure 8 6 Counting names in a list Write a program that will count the number of times a search name appears in a list of names Use the algorithm you have seen in the counting occurrences animation to help 45 min you Remember to construct appropriate test cases in advance of coding You should consider tests which check for e boundary conditions e g occurrence of the search value at the beginning or end of the list no occurrences of the search value within the list a single occurrence of the search value multiple occurrences of the search value 8 5 4 Finding Maximum Computers are often used to find maximum and minimum values in a list For example a spreadsheet containing running times for videos might make use of a maximum algorithm to identify the video with the longest running time or a minimum algorithm to identify the shortest running time A database containing personal details of club membership might make use of maximum and minimum algorithms to identify the oldest or youngest
86. T WATT UNIVERSITY ANSWERS TOPIC 6 249 Answers from page 129 Q17 d Q18 a Q19 c NOT 11 The execution of program statements in order from beginning to end Q20 b The expression is TRUE when both conditions being tested are TRUE Q21 c Assignment Outwith range page 129 Answer to come HERIOT WATT UNIVERSITY 250 ANSWERS TOPIC 7 7 High Level Language Constructs 2 Revision page 147 Q1 c Data items of the same type are grouped together Q2 d Days 3 Wednesday Q3 c 1 8 3 9 5 6 Answers from page 157 Q4 d Control loop variable is increasing in value by a constant amount determined by the programmer Q5 d For loopCounter 3 4 16 to 5 5 6 step 1 Q6 a Calculating the total number of marks entered at a keyboard Q7 a Triangle Q8 c 18 Answers from page 165 Q9 The value of n within the loop is never incremented It will therefore always have a value of 0 which is less than 100 and hence this will produce an infinite loop which will never terminate The program will therefore never end The code could be altered to include an increment i e n 0 do while n lt 100 value n n n n i loop Q10 There is no loop to end the do while Add loop at the end of the code i 1 do while i lt 10 print i i i 1 loop Q11 A typical solution to the problem is shown here dim i as integer sum as integer sum 0 i 0 do while i lt 20 sum sum i i a
87. To count 1 Count 1 s and 2 s If HeadsTails toss 1 Then heads heads 1 Else tails tails 1 End If Next toss PicHeads Print heads Display results PicTails Print tails PicTosses Print count End Sub This file Heads Tails txt can be downloaded from the course web site Code 38 Note that to make the program easier to follow two for next loops are used but they could be combined into a single loop Coding the Palindrome Checker page 189 When you do code it successfully you will have results like those shown in Figure 9 1 HERIOT WATT UNIVERSITY ANSWERS TOPIC 7 253 Palindromes Figure 9 1 There are other methods probably much simpler of writing programs to test for palindromes However it is essential that you understand the use of arrays since they are important data structures in all fields of computing You will see more in the use of arrays in the final topic HERIOT WATT UNIVERSITY 254 ANSWERS TOPIC 8 8 Procedures Functions and Standard Algorithms Revision page 193 Q1 b That the input data is within specified limits Q2 dj All of the above Q3 b A sequence of instructions that can be used to solve a common problem Program with parameters page 197 Private Sub Get_valid_number gt input validation Dim Number As Integer Dim Inrange As Boolean Do Number InputBox Enter a number in the range 1 to 30 Inrange Number gt 1 AND Number lt 30 If no
88. UAGES 73 5 7 1 Benefits of scripting languages One of the main benefits of scripted languages is that they require no compilation The language is interpreted at run time so the instructions are executed immediately Scripting languages also have a simple syntax which for the user makes them easy to learn and use assumes minimum programming knowledge or experience allows complex tasks to be performed in relatively few steps allows simple creation and editing in a variety of text editors allows the addition of dynamic and interactive activities to web pages 5 7 2 Examples of Scripting Languages Specialised scripting languages include Perl Practical Extraction and Report Language This is a popular string processing language for writing small scripts for system administrators and web site maintainers Much web development is now done using Perl Hypertalk It is the underlying scripting language of HyperCard while Lingo is the scripting language of Adobe Director an authoring system for develop high performance multimedia content and applications for CDs DVDs and the Internet AppleScript a scripting language for the Macintosh allows the user to send commands to the operating system to for example open applications carry out complex data operations An example script is shown in Code 3 this simple Applescript will search recursively through folders in a shared volume removing certain unneeded files from e
89. able components Trace facility A method used to debug a program by tracing the change in values of the variables as the program is run Traditional model An alternative name for the waterfall model that details the seven stages of program development Unusual user activity Running a program with exceptional data User guide A document intended for people using a system containing information on how to use the software HERIOT WATT UNIVERSITY 239 240 GLOSSARY Value parameter Here a copy of the actual parameter is passed in to the formal parameter Information is passed IN to the procedure form the main program Waterfall model One of the earliest models for software development that incorporates 7 stages from analysis to implementation and maintenance HERIOT WATT UNIVERSITY HINTS 241 Hints for activities Topic 6 High Level Language Constructs 1 Calculating minutes Hint 1 This problem naturally breaks up into four sections 1 declare the variables 2 get input 3 calculate the minutes 4 output results The input must consist of three numbers the days the hours and the minutes So you need three variables to hold these figures What will you name them What type will they be integer real How do you work out the total number of minutes from these figures You have to design a section of code to do this Hint 2 There are 60 minutes in one hour and 24 hours in a day hence 720 24 60 1
90. al memory addresses as such but simply refer to the data positions within the array In Visual BASIC the first element usually has index 0 Imagine you were to process the average temperature data in Edinburgh for the last 30 days If each of the day s temperatures are stored as separate variables you would require 30 distinct variables and the storage and manipulation of these variables becomes difficult To overcome the above problem you can define a variable called temperature which represents not a single value of temperature but an entire set of temperatures This is illustrated in Figure 7 12 showing an array structure called temperature and elements with the subscript ranging from 0 to 8 HERIOT WATT UNIVERSITY 7 8 ARRAYS 175 temperature 1 temperature 6 012 3 4 5 6 7 8 Index or subscript Figure 7 12 Representation of an array and indices An individual array element can be used anywhere that a normal variable could be e g temp temperature 27 average temperature 5 temperature 6 2 0 A value can be stored in an array simply by specifying the array element on the left hand side of the assignment operator equals sign e g temperature 2 18 0 assigns the value 18 0 to be stored in element with subscript 2 of the temperature array temperature 7 14 5 assigns the value 14 5 to be stored in element index number 7 of the temperature array This is illustrated in Figure 7 13 temperature I
91. alue number3 InputBox Please enter a value Sum numberi number2 number3 PicDisplay Print PicDisplay Print Output using commas PicDisplay Print numberi number2 number3 Sum PicDisplay Print Output using semi colons PicDisplay Print numberi number2 number3 Sum PicDisplay Print End Sub Run the program using your own values of number1 number2 and number3 Your output should look like the following HERIOT WATT UNIVERSITY 6 3 BUILDING APPLICATIONS 93 Formatted output Use of TAB and SPC Two valuable print functions are TAB and SPC that allow for more formal results TAB 6 will begin output 6 units from the left margin SPC 6 will output 6 units from the previous output Exercise 5 Modify the previous code as follows and run the program PicDisplay Print PicDisplay Print Tab 2 numberi Tab 14 number2 Tab 26 number3 Tab 38 Sum PicDisplay Print PicDisplay Print Spc 4 number1 Spc 9 number2 Spc 9 number3 Spc 7 Sum HERIOT WATT UNIVERSITY 94 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 This time you end up with the output that should look like the following Formatted output You will learn more about formatting values later 6 4 Program Structure A typical Visual BASIC program takes the form shown in Code 5 Option explicit General area Public or Global variables declared here Private Sub cmdClick_Click constant definiti
92. am However the names can be different HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 203 For example Private Sub Do_calculations byRef name as String byRef age as integer byRef dob as String is WRONG because the parameters are listed in the wrong order but Private Sub Do_calculations byRef x as String byRef y as String byRef z as integer would be fine because although the names are changed the parameters are listed in the correct order so VB would know that x corresponds to name y to dob and z to age You can use the same names for both formal and actual parameters if you want to However using different names allows a sub program to be included in a module library and used in different contexts without having to change the variable names within the procedure byVal or byRef Consider each of the following situations and decide whether the parameter needs to be called passed by Ref or by Val Q4 Interpreting mouse movements a byRef b byVal Q5 Checking there is sufficient RAM to load a program a byRef b byVal Q6 Keeping track of where documents are stored a byRef b byVal Q7 Sending data to a printer a byRef b byVal 8 2 1 4 Call by Value Call by value is the most common parameter passing mechanism andis also the easiest to understand It is used when a data item is to be passed IN to a procedure Recalling the section of code that outputs blank lines we can now introd
93. ample Single or double Problem A program is written to prompt the user for a number If the number entered by the user has a single digit then the program will display an appropriate message telling the user that this is single digit number Otherwise it will output the message double digit number The algorithm is shown below Solution 1 Ask for user to input number between 1 and 99 2 if the number lt 10 3 display single digit number 4 else 5 display double digit number The full Visual BASIC program is seen in Code 12 Option Explicit Private Sub Commandi_Click program simple_If_Then_Else 15th February 2004 gt Program by Fred Fink gt This program will prompt the user to enter a number gt The program will test the number to see if it is less than 10 and print the message that it is a single digit number Otherwise it will output double integer number Dim testNumber As Integer testNumber InputBox Please input a number If testNumber lt 10 Then PicDisplay Print testNumber is a single digit number Else PicDisplay Print testNumber Is this double digit number End If End Sub Private Sub cmd_Exit_Click End End Sub This file IfThen txt can be downloaded from the course web site Code 12 HERIOT WATT UNIVERSITY 6 13 THE IF THEN ELSE STATEMENT 121 Note that this program has an extra procedure Sub cmd_Exit_Click You have probably found that Visual BASIC p
94. anywhere in the program Private within the General section of a form or module makes the array visible only to the form or module in which it s declared Note that in Visual BASIC when an array is declared the first index is 0 by default It s possible in some versions of Visual BASIC however to force the first element of an array to be 1 by using the To statement All this will make sense with a few examples 1 Declare an array called MyName to hold 6 integer values Dim MyArray 5 As Integer 2 Declare an array called Names to hold 3 string values Dim Names 1 to 3 As String 3 Declare a public array called Numbers to hold 50 decimal values Public Numbers 49 as single Note Visual BASIC NET does not support declarations using to Common errors associated with arrays 1 Note that you cannot mix the types of data stored in an array So a single array cannot be used to store integer real or string variables together 2 The most common error is to attempt to access an array element outwith the declared bounds e g accessing element 0 or 15 of an array with subscript range specified as 1 14 This type of error is so common that it has been given the name fencepost error It is not a minor error as it can crash the system HERIOT WATT UNIVERSITY 7 8 ARRAYS 177 7 8 3 Simple 1 D array manipulation Example 1 Using an integer variable to initialise an array Problem How can the array temperature be initialis
95. are problem oriented Program statements and expressions in such languages generally incorporate English words which mean that they are easier to understand and use than machine code There are many programming languages that could be used for the implementation phase of software development such as C and C Pascal and Java Older languages still much used include COBOL and Fortran COBOL is used mostly on mainframes for batch processing organisations still use it for new programs because all their old HERIOT WATT UNIVERSITY 64 TOPIC 5 LANGUAGES AND ENVIRONMENTS programs are written in it Fortran is still used for applications where the emphasis is on numerical processing such as processing meteorological data In this topic and others all language features are exemplified using Visual BASIC The choice of language should be based on which language has the facilities most appropriate to solving the required problem a suitable compiler interpreter available for the client hardware 5 3 Classification of High Level Languages At the time of writing it has been estimated that around 2 500 programming languages have been catalogued over the years Programming languages For further information and a chance to download a time line of language development as a poster consult the following links http people ku edu nkinners LangList Extras langlist htm http www levenez com lang history html 08 Look up any
96. ary and meaningful variable and procedure names Stub A temporary addition to a program used to assist with the testing process Symbol table Part of the compilation process where the tokens created by the lexical analysis phase are stored Syntax Syntax means structure or grammar of a statement in a given language HERIOT WATT UNIVERSITY GLOSSARY Systems analyst The person responsible for analysing and determining whether a task is suitable for pursuit using a computer They are also responsible for the design of the computer systems Systems developer Another name for a systems analyst Systems specification An indication of the hardware and software required to run the developed program effectively It will be the basis of subsequent stages which prepare a working program Technical guide Documentation intended for people using a system containing information on how to install software and details system requirements such as processor memory and backing storage Test data Data that is used to test whether software works properly and that it is reliable and robust Testing Running a program with test data to ensure a program is reliable and robust Test log A record of how a program responds to various inputs Test plan A strategy that involves testing software under verifying conditions and inputs Top down design A design approach of sectioning a large and complex system into smaller and more easily manage
97. at the implementation stage will call for a return to an earlier stage of the development process For example it might turn out that an HERIOT WATT UNIVERSITY 2 5 THE IMPLEMENTATION STAGE algorithm runs too slowly to be useful and that the designer will have to develop a faster algorithm Or it might be that the slowness of operation is due not to a poor algorithm but to the hardware capability In such a case the development team might have to return to the analysis stage and reconsider the hardware specification At the end of the implementation stage a structured listing is produced complete with internal documentation This will be checked against the design and against the original specification to ensure that the project remains on target 2 5 1 Debugging At this stage the programming team will make use of test data This data is designed to check that the program works properly and that it is reliable and robust Testing is often confused with the debugging of a program but these are not the same though they are very closely related e testing discovers any faults in a computer program debugging is the finding and correcting of these faults Maintainable software should include internal documentation This is commentary within the program to explain the various stages and to record any changes that might be implemented in the coding during debugging One aspect of this is the use of meaningful variable names 2 5
98. ata Cea ach al Pa A RE A ee a Pa de 44 3 3 1 Review questions 44 3 4 Structured iStIAQ goed ME has pee Gun arts Grange Had woe dtd deg 45 3 5 Error Reporting vs wis Ose ie koe an LE arte kre ae se SER ES 46 3 67 SUMMAFY seo 8 PM ARLE BAS Pan he ES Sale RAE Be 47 327 EndortopiGteSt 2 4 amp amp amp a at eae we ete BAKA oe ow arc a 47 Prerequisite knowledge Before studying this topic you should be able to e describe and use pseudocode e describe and use a graphical design notation structure diagram or other suitable method Learning Objectives After studying this topic you should understand the nature of graphical design notations e be able to use a graphical design notation understand the nature of pseudocode e be able to use pseudocode understand the nature of top down design and stepwise refinement 35 36 TOPIC 3 TOOLS AND TECHNIQUES e be able to describe the main types of error be able to explain how good test data can reduce errors HERIOT WATT UNIVERSITY 3 1 INTRODUCTION 37 Revision 7 Q1 Atthe design stage of the software development process pseudocode may be used to represent a solution to a problem Which of the following best describes pseudocode a It uses ordinary English words b Itis high level language dependant c Itis very useful in complex program designs d It mostly uses high level language key words Q2 A structure diag
99. atically to the next Example of simple sequence The program examples you have seen so far follow simple sequences Try the following activity Problem A program is written to ask the user to enter a number at the keyboard The program then doubles it and displays the result on the screen request a number from the user get the number typed in by the user double the value of the number display the new value on the screen e NN FE Sequential control of a program limits the type and range of problems that can be solved Sequence is basic and essential but limited A program in simple sequence always does the same sort of thing and it can t easily do things more than once HERIOT WATT UNIVERSITY 116 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 We want programs that can carry out tests and make decisions We want programs that can do things over and over again With the use of selection and repetition the range of problems that can be solved becomes much larger This is what we will look at next 6 11 2 Selection A fundamental task in any program is the decision of what to do next Control constructs enable you to make decisions in your programs to determine when certain parts of the program will be executed In a similar manner to English you can make decisions using the if statement for example if it is raining then will take my umbrella In this topic you will look at the following control constructs and how to
100. ay 3 2 5 O Q25 Write a program that will set each element in an array called myarray of 10 elements to the value of its index The contents of the array are then printed out in a vertical line 7 8 4 Review Questions Q26 Initialising a 1 dimensional array means a Setting all locations of an integer array to O zero b Setting all locations of a string array to null c Setting all locations of a real array to pre determined values d All of the above options Q27 The contents of a string array message contain the following characters in successive memory locations HAPPYBIRTHDAY The programming structure required to produce the above message could best be achieved using choose one HERIOT WATT UNIVERSITY 7 8 ARRAYS 181 A case statement A for loop A while loop a b c d An until loop YS er waa na Q28 An array numbers is declared with 6 elements and initialised to contain the following values 030259 During a program run the array elements are changed as follows numbers 2 6 numbers 5 7 numbers 1 4 The array contents are now a 030259 b 430259 c 460270 d 046257 Q29 An array value_1 has been declared in Visual BASIC to be of type single and to hold 5 values Which one of the following statements would produce an error when the program is run a value_1 0 Hello b value_1 4 89 45 c value_1 1 5 6E37 d value_1 2 16 Q30 What is the least
101. be disappointed with the results Many developers value feedback from clients as the project progresses 5 Errors arising from incorrect requirements will not be obvious until late in the cycle by which time they will be difficult and expensive to fix There is nothing so depressing as delivering months sometimes years of work to the customer only to be greeted with the response That s not what wanted at all 2 11 Summary The following summary points are related to the learning objectives in the topic introduction e the software development process has 7 stages analysis design implementation testing documentation evaluation maintenance e the process is iterative and involves a continual revision and evaluation at each phase of the process 2 12 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY 33 34 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS HERIOT WATT UNIVERSITY Topic 3 Tools and techniques Contents Ses Introduction 5 eee is pepe ae pape Ee ROL RS Gee 37 3 2 Design methodologies and notations 38 8 2 1 Top down design with stepwise refinement 38 3 2 2 Structure charts diagrams 40 8 2 3 Interpreting Structure Charts 40 8 2 4 Pseudocode 41 3 2 5 Review questions 43 3 3 Test D
102. ble expression This statement says make left hand side equal to the right hand side It makes the variable take on the same value as expression You have already seen this used in previous programs For example circumference 2 PI r where the result of the expression 2x PI ris assigned to the variable circumference Arithmetic operators Table 6 5 list the main arithmetic operators in Visual BASIC Table 6 5 a CEST surac real division DIV 27 83 3 muti mod modulus operator It is important to remember that integer division gives you a whole number answer only any remainder is discarded For example 5 2 gives 2 as the answer 16 5 gives 3 as the answer The modulus operator is used for division to obtain the remainder The expression x mod y HERIOT WATT UNIVERSITY 6 10 OPERATORS produces the remainder when x is divided by y The mod operator can be applied to integers and also with real For example 5 mod 2 gives 1 8 mod 3 gives 2 9 mod 3 gives 0 zero 7 1 mod 3 1 gives 1 numbers rounded down 10 8 mod 3 6 gives 3 numbers rounded up Questions on Mod and Div Q14 7 Mod 2 a 3 5 b 3 c 1 d 49 Q15 7 2 a 3 5 b 3 c 1 d 49 Q16 7 2 LOTS RoW oO 6 10 1 Operator precedence When several operations occur in an expression each part is evaluated and resolved in a predetermined order called operator precedence Parentheses can b
103. bles which are linked together These links are called relations and such a database is known as a relational database The fields that are to be in the tables and the relations between tables need to be defined at the design stage Object oriented design attempts to treat data and objects together An object brings together items of data and the operations that can be carried out on it For example a data item might be a customer s record and the operations might include creating displaying editing and deleting 2 4 4 Other design choices The system specification and functional specification will form the basis for designing the program The design team must consider hardware specification e choice of high level language e choice of operating system e portability of the system Hardware aspects will include processor speed does the program require multiple processors for optimum performance as in networked database applications or maybe maximum memory for caching information on a regular basis How much external storage is required for say regular backing up procedures and on what medium This is an important issue especially on networked systems where users files are archived on a daily basis A high level language will be chosen that is best suited to the problem but also one which the programming team is conversant with and proficient in its use Modularity will be an important issue where the team can share the workload
104. by breaking it down into small steps each of which can be written in Visual BASIC you will chip away at the problem until it is done The solution to this problem assumes that you do not know how many words are going to be input Design Solution Notes on Section 2 The program does not know how big a sequence will be entered so an array of characters larger than required must be declared The program reads in the sequence of characters one at a time into the array terminated by a full stop It also checks that the array bounds are not breached by testing the condition count lt Size using a do while loop This is important otherwise an array bounds error will likely occur The constant Size is initially set to 30 but may be altered if large strings are used The condition in the while do loop that checks whether was the last character entered is palindromeChar lt gt gt lt gt means not equal to Notes on section 3 Once it has completed reading in the characters you can determine the number of values read in This is count 1 not count since you are not interested in the last character All it contains is the termination character which you do not want to use in HERIOT WATT UNIVERSITY 7 8 ARRAYS 187 the rest of the program Now you are ready to see whether the string is a palindrome The array is searched through comparing the 1st element with the last the 2nd element with the 2nd last
105. by compiling modules independently thereby reducing the overall development time Module libraries can be a source of standard algorithms to be used in software projects of many types Choice of operating system will relate to the functionality and feel of the HCI Windows might offer much in the way of colourful screens interactive help and dialogue boxes etc It must also affect how the program runs and behaves is the OS software stable enough for the developed program to behave normally without crashing or does the OS offer a true multi tasking environment as in UNIX with the added benefits of in built security Nowadays Linux is being seen as a viable operating system which is both stable and not difficult to use If the developed software can be moved to different machine architecture and still run to specification then it will be deemed to be portable In some cases this might not be required but it is a characteristic that good software should possess HERIOT WATT UNIVERSITY 20 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS 2 5 The Implementation Stage If the design has been thorough the implementation should be straightforward It should be a matter of design translating the pseudo code into code line by line implementation testing documentation evaluation maintenance LL A oc et i a lt The design is implemented when it has e m been converted into code which can be
106. can make running a program a less irritable experience Q14 c Assembler Q15 d Source code Answers from page 26 Q16 b Testing is done within the organisation Q17 a The program is tested by the clients Q18 a The input of unexpected data HERIOT WATT UNIVERSITY 244 ANSWERS TOPIC 2 Answers from page 30 Q19 c The program can cope with mistakes that the user might make Q20 d The program runs to specification Q21 d All of the above HERIOT WATT UNIVERSITY ANSWERS TOPIC 3 245 3 Tools and techniques Revision page 37 Q1 c It is very useful in complex program designs Q2 d They represent the design in a visual way Q3 b English and high level language code Answers from page 43 Q4 a Structure charts Q5 b Itis breaking complex problems down into smaller units Q6 c Stepwise refinement Q7 a Think more about the solution to the problem Q8 d The designer can concentrate on a small part of the problem at a time Preparing test data page 44 Q9 Sample solution 1 0 to 100 2 Loop Enter user input If user input invalid then report error message Until input is valid 3 in first 2 columns 5 valid data 0 boundary extreme data 95 valid data 100 boundary extreme data 10 exceptional should be rejected 110 exceptional should be rejected A exceptional should be rejected 10 5 may be valid or exceptional specification does not make clear whether or not real numbers s
107. ching a list of names Adapt the previous program so that it that will search a list of names for a given name You should consider the following tests where the name does not appear in the list appears at the start of the list appears at the end of the list appears within the list HERIOT WATT UNIVERSITY 8 5 STANDARD ALGORITHMS 221 8 5 3 Counting Occurrences Programs often have to count occurrences Examples include counting the number of e students who achieved particular marks in an examination e rainfall measurements greater than a particular level words equal to a given search value in a text file The basic mechanism is simple 1 acounter is established 2 alist is searched for the occurrence of a search value 3 every time the search value occurs the counter is incremented There is an interactivity online which you should attempt now You should notice that counting occurrences examines the entire list and so the algorithm is a variation of the linear search algorithm described above The general counting occurrences algorithm is Counting occurrences general algorithm 1 counter 0 2 prompt the user for the search key 3 set pointer to start of list 4 do 5 compare search key to list position 6 if equal then 7 increment count 8 end if 9 move to next position in the list 10 until end of list 11 report number of occurrences Below is a Visual BASIC implementation O
108. cient It should not make unreasonable demands on the hardware on which it will run But higher efficiency can lead to less maintainable software as programmers use shortcuts which are effective but difficult to understand 4 the software should have an appropriate user interface Appropriate means that you need to consider the background and capabilities of intended system users There is often a trade off between these factors and the cost of producing the software This is illustrated in the diagrams in Figure 1 1 As you can see costs increase dramatically as developers attempt to provide software that is 100 percent reliable Making software more efficient also increases the amount of money that needs to be invested cost cost efficiency Reliability Figure 1 1 Cost of Software Systems HERIOT WATT UNIVERSITY 8 TOPIC 1 THE NEED FOR THE SOFTWARE DEVELOPMENT PROCESS 1 5 Summary The following summary points are related to the learning objectives in the topic introduction e the software development is a complex process involving many facets of professional expertise no matter how simple or complex a program is the elements of software development are almost mandatory to ensure well planned programs no matter how rigorously the software development process is followed errors can still occur in large commercial software systems 1 6 End of Topic Test An online assessment is provided to help you rev
109. clare constant PI and assigns value Dim radius As Single Dim circumference As Single radius InputBox Please enter the radius of the circle circumference 2 PI radius Print The circumference of circle with radius radius is circumference End Sub This file Circle txt can be downloaded from the course web site Code 8 In this program an Input Box is used for input and a Print statement sends output direct to the form see Figure 6 5 and Figure 6 6 Circle Please entei the radius of the circle Figure 6 5 HERIOT WATT UNIVERSITY 6 8 DECLARING CONSTANTS 105 Form The circumference of cirde with radius 7 5 is 47 12385 Calculate Circumference H ROTTCEOEEEEEEEEEE EE LEE PE EEE EEE EEE EEE EEE EEE EEE EEE Figure 6 6 Note that this method uses multiple windows Input is via an inputBox and output is on the form itself using the print command A VB project 1 create a new VB project 2 create a form based on Figure 6 6 and name the button cmdCircle AU imin 3 enter the code for clicking the command button you can cut and paste Code 8 4 run the program to check it works correctly 6 8 2 Example program 2 Use of a boolean variable Problem A program is required to display whether a number entered at the keyboard is greater than or equal to zero The program will prompt the user to enter a number It will then display a message together with the value true or
110. ct window that displays the files that are created during the construction of the program These files could be forms modules blocks of code not attached to a form graphics or control structures such as Active X required for the successful running of your program Note that only one project can be open at any given time 3 a Properties window that displays the properties of the objects created in the program The form window itself has properties associated with it 4 a Toolbox window that consists of all the controls necessary for developing a program Boxes labels buttons and other objects can be drawn on the form as part of the visual interface and also to allow input and output of data At this stage it is important to realise that when you create a program each form module graphic and ActiveX control is saved as an individual file Table 6 1 shows the common files types in a Visual BASIC Project Table 6 1 File Type FRM BAS OCX Class module VBP Visual BASIC project When starting to write Visual BASIC programs the two most common file types are Form and Project 6 3 Building applications Constructing a program in Visual BASIC involves two processes 1 creating the visual design of the program 2 designing and implementing programming code 6 3 1 Creating a form and objects In the first process the properties of the form are established followed by the creation of controls inside the form The prop
111. d potential users to determine the exact nature of the problem They define the goals of the system and divide the solutions into individual steps and separate procedures Full systems analysis has three phases 1 collection of information 2 analysis of information collected 3 production of a problem specification or user requirements specification Systems Analyst Research pe Use the internet to find 4 adverts for systems analyst jobs and use the information to a Le complete the following table job tite salary skills experience required 4 4 1 Collection of Information There are various methods used for gathering information These include a Interviews The analyst talks face to face with clients to find out how the current system works and what is required of the new system The analyst seeks answers to the obvious questions beginning with these words e what does the system do e where are these things done e when are they done e why are they done e and who does them Many of these techniques are essentially iterative The answers to questions often raise further questions which the analyst must go and ask and so on b Questionnaires Where the current system has a large number of users the analyst might construct a questionnaire for everyone involved People often respond more frankly to an anonymous questionnaire On the other hand the response rate can be low HERIOT WATT UNIVERSITY 54
112. design testing evaluation Q OO 0 9 HERIOT WATT UNIVERSITY 13 14 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS Q5 The software development process may involve iteration Which one of the following statements is true if iteration is used a The team may go back to an earlier stage to deal with a problem b The software is guaranteed to be error free c Each stage is carried out twice d Once all the stages have been completed the team go back and start again Q6 Software developers cannot get the software correct at the first attempt This is because Software systems can be very complex Unforeseen errors always creep in that take time to solve There could be problems with the client changing his her mind All of the above a b c d Q7 Regular feedback of information to members of the development team is important This is done in order to Speed up the development process Enable personnel to discuss progress Keep the team happy a b c d Lower the costs on a regular basis Sentence completion software development process On the Web is a sentence completion task on the software development process You should now complete this task 2 3 The Analysis Stage This stage is crucial to the entire cycle of events Any problems occurring at this stage will be propagated design through the system and will become increasingly costly to rectify when discovered implem
113. designed to add functions to or automate some aspect of either an application program or an operating system Scripting languages support high level language control features such as selection and iteration Examples of present day scripting languages are VBScript JavaScript Perl Python and TCL Tool Command Language Applications that provide scripting capability allows the user to extend the functionality of the application by programming a sequence of actions For example in Filemaker Pro a database package it is possible to write scripts that open and close files copy data from records or enter a certain database mode such as browse or find An example script in Filemaker Pro is shown in Code 1 Enter Browse Mode Go to Layout Layout 1 Enter Find Mode Set Field Computing Course S3C8 Perform Find Sort Restore No Dialog Go to Layout S3 Report Final Code 1 Another example is VBScript which is a cut down version of Visual BASIC used to enhance the features of web pages in Internet Explorer Below in Code 2 is an example of a section of VBScript embedded in HTML code lt HTML gt lt HEAD gt lt TITLE gt This is VBScript in action lt TITLE gt lt SCRIPT LANGUAGE VBScript gt MsgBox Welcome to VBScript lt P gt Click on the button below lt P gt lt INPUT TYPE Button NAME cmdClick VALUE Click gt lt SCRIPT gt Code 2 HERIOT WATT UNIVERSITY 5 7 SCRIPTING LANG
114. e Test and gets the numerical value 10 Formal parameter number now has the value 10 4 Procedure Change code is activated and both number and Test 20 8 2 1 6 Comparison of Call by Value and Call by Reference How do Call by Value and Call by Reference work If you have access to the web version of SCHOLAR you should view the animated version of the following explanation Consider the previous program If Call by Value is used the process is 1 The Procedure call Add_10 Test is initiated 2 The Procedure declaration Add_10 is accessed HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 209 Within the procedure a local copy of the variable Test is made named Number The Procedure adds 10 to the value stored in Number The procedure terminates O a Aa O Control returns to the main program Test still has the value 10 If Call by Reference is used the process is 1 The Procedure call Add_10 Test is initiated 2 The Procedure declaration Add_10 is accessed 3 The Procedure accesses the main program variable Test directly and treats it as though it is the local variable Number 4 The Procedure adds 10 to the value stored in Test 5 The procedure terminates 6 Control returns to the main program Test now has the value 20 Don t worry if you have found the material in this section difficult to follow first time round Remember if a parameter is used only to transmit a value to a proced
115. e order of precedence e g 4 5 2 9 2 18 and so 4 5 2 is equal to 18 Example 3 Operator precedence 3 7 5 42 4 Problem What is the result of 3 7 5 12 4 Solution The expression in brackets is evaluated first then exponentiation followed by multiplication then addition i e 3 7 5 72 4 3 2 2 x 4 3 4 4 3 16 19 and so 3 7 5 2 4 is equal to 19 HERIOT WATT UNIVERSITY 6 11 PROGRAMMING CONSTRUCTS 115 Matching operations and results On the Web is an interactivity You should now complete this task 6 11 Programming constructs Structured programming is based on three constructs sequence selection repetition 6 11 1 Sequence This is the computer s basic mode of operation This is how it s designed to work A computer is designed to carry out an instruction and move automatically onto the next instruction A program is working in sequence when it e begins at the beginning carries out each statement or instruction once and only once e stops when it s reached the end In other words it misses nothing out which happens under selection and it does nothing more than once which happens under repetition Sequence is the default mode of operation for a program a program works in sequence unless it is explicitly told to do otherwise by means of one of the other programming constructs Left to itself it will always carry out a statement and proceed autom
116. e program is one that does not stop because of faults in its design A robust program is one that can cope with errors when it is running To put it another way an unreliable program is one that hangs or crashes for no apparent reason whereas a non robust program is one that cannot cope with events that the world HERIOT WATT UNIVERSITY 2 4 THE DESIGN STAGE 17 throws at it Identifying the characteristics of good software design On the Web is an interactivity You should now complete this task 2 4 1 Review questions Q8 Which one of the following processes describes breaking a complex system down into more manageable components top down design using pseudocode refined design prototyping Q9 Inthe software development process which of the following is a legal contract a functional specification b problem specification c requirements specification d software specification Q10 Which of the following are identified during the analysis stage of software development the main costs of the project time taken to complete the project hardware required to run the system d All of the above Q11 The completed software system should be able to cope with many errors while running This means that the software is choose one a Portable b Robust c Reliable d Stable Q12 Which of the following is included in the functional specification a description of what the software must do the hardware u
117. e the output Lo dy Das 8 Dy SO mumheses Because the output is First and Second the value of Count is halved otherwise the output would be twice that required i e Do Until Count NoUfTerms 2 2 Also the value of NoOfTerms is decreased by 2 to take into account the first two values which are output first and are not part of the loop Sample program output is shown in Figure 7 11 HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 171 Fibonacci Fibonacci numbers 11235813 21 34 55 89 144 233 377 610 987 No of terms Run Program Figure 7 11 7 6 9 Review Questions Q12 Which one of the following statements is true regarding the do while loop The conditional statement is always satisfied The block of code is entered first before the condition is tested The loop need not be entered if the condition fails at the start The loop terminates when the condition becomes true a b c d Q13 Looping structures have several features in common Which one of the following is NOT one of these features a Selection b Increment c Initialisation d Condition Q14 What is the output of the following program fragment that uses a do while loop i 0 Do i i i Print i Loop While i lt 5 a 01234 b 12345 c 012345 d 123456 HERIOT WATT UNIVERSITY 172 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Q15 In the previous example the do while loop is replaced by a do until loop as follows
118. e used to override the order of precedence and force some parts of an expression to be evaluated before other parts Operations within parentheses are always performed before those outside Within parentheses however normal operator precedence is maintained When multiplication and division occur together in an expression each operation is evaluated as it occurs from left to right Likewise when addition and subtraction occur together in an expression each operation is evaluated in order of appearance from left to right Arithmetic operators are evaluated in the following order of precedence HERIOT WATT UNIVERSITY 113 114 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Arithmetic operator precedence Parentheses Exponentiation Negation Multiplication and division Integer division Modulus arithmetic Mod Addition and subtraction Operator Precedence Online there is an interactivity which you should complete now Example 1 Operator precedence 4 5 2 Problem What is the result of 4 5 2 Solution The multiplication is calculated first then the addition since multiplication has a higher precedence than addition e g 4 5 2 4 10 14 and so 4 5 2 is equal to 14 Example 2 Operator precedence 4 5 2 Problem What is the result of 4 5 2 Solution The expression in the brackets is calculated first then the multiplication the brackets have altered th
119. ed on its own the print statement with no explicit destination will produce output to the current window which in most cases is the Visual BASIC form HERIOT WATT UNIVERSITY 92 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 For example if X 5 and Y 7 the following statement will output a text string and value to the form Print The sum of the two variables X and Y is X Y If the form is populated with many objects it may be difficult to see the above output It is much better therefore if the output is directed to a specified window such as a MessageBox TextBox or PictureBox Although a PictureBox is meant for graphics it is also ideal for the output of lists of text Using a PictureBox the previous print statement would become PictureBox Print The sum of the two variables X and Y is X Y Usually the term PictureBox is changed to PicBox PicOutput PicDisplay Picture1 or whatever name is suitable for the output Exercise 4 Create a new project and place a command button and PictureBox on the form Rename the PictureBox as PicDisplay and the command button as cmdAdd Double click on the command button and enter the following code The first and last lines are present by default so they can be ignored when entering the text Private Sub cmdAdd_Click Dim numberi As Integer number2 As Integer number3 As Integer Dim Sum As Integer numberi InputBox Please enter a value number2 InputBox Please enter a v
120. ed out repeatedly HERIOT WATT UNIVERSITY 5 4 PROCEDURAL IMPERATIVE LANGUAGES 67 Both iteration and selection are control constructs because they can alter the flow of control of program execution You will see more of this in later topics Examples of procedural languages are Algol Fortran Pascal BASIC C and COBOL Example of a program to read data into an array and output results Problem In Visual BASIC we might tell the computer how to input data into an array and then print out the results Solution gt Program to fill an array with team names and print them out Private Sub FillArray_Click Dim Team 5 As String Dim Count As Integer Assign array values Team 0 Leith Learners Team 1 Bonaly Boys Team 2 Royston Rovers Team 3 Calder Colts Team 4 Juniper Juniors Team 5 Wardie Wanderers For Count 0 To 5 Print Teams Tab 8 Count 1 Tab 14 Team Count Next Count Print End Sub Notice that 1 the program is expressing at each step precisely how each statement is executed 2 the program has beginning and end points which is an indicative feature of procedural language programs HERIOT WATT UNIVERSITY 68 TOPIC 5 LANGUAGES AND ENVIRONMENTS The program output is ormi Leith Learners Bonaly Boys Royston Rovers Structures in procedural languages On the Web is an interactivity You should now complete this task 5 4 1 Review Questions
121. ed to ask the user to guess an age the value of which is stored as a program constant The program should count the number of tries needed to guess the correct age and declares whether the guesses are high or low Solution The algorithm is shown below 1 set the number of guesses to 0 2 do 3 add 1 to the number of guesses 4 request an age from the user 5 if guess gt age output message too high 6 elsif guess lt age output message too low T endif 8 loop until guess age 9 display The number of times guessed The Visual BASIC program is shown in Code 27 Option Explicit Private Sub Commandi_Click program MyAge 17th February 2004 gt Program by Fred Fink This program will prompt the user to guess an age which is stored gt in the program as a constant It will display the number of attempts needed to guess the correct age Const MyAge As Integer 21 again Dim ThisGuess As Integer guesses As Integer guesses 0 Do ThisGuess InputBox Guess my age guesses guesses 1 HERIOT WATT UNIVERSITY 167 168 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 If ThisGuess gt MyAge Then PicDisplay Print ThisGuess is too high ElseIf ThisGuess lt MyAge Then PicDisplay Print ThisGuess is too low End If Loop Until ThisGuess MyAge PicDisplay Print Ok so its MyAge amp but it took you guesses tries End Sub This file GuessAge txt can be downloaded from the course web
122. ed to zero using a for loop Solution A typical solution to this problem is shown here for count 0 to 4 temperature count 0 next count The first time round the loop the variable count has the value 0 and so the element with index number 0 of the array temperature is set to 0 The next time round the loop count has been incremented by 1 and has the value 1 and so element index number 1 of the array will be set to 0 and so on This one simple loop replaces 5 lines of code i e temperature 0 temperature 1 temperature 2 temperature 3 temperature 4 Il Example 2 Displaying the contents of an array Problem How can the contents of an array be displayed using a for loop Solution If you assume you have an array called Store which has 6 elements then you could use the following code to display the contents of each element for count 0 to 5 Print element count Store count next count For example if the array Store held the values 3 12 4 6 3 2 0 1 see Figure 7 14 Store POZORE 0 1 2 3 4 5 Figure 7 14 Contents of a six element array Store Then the output would be Element 0 3 Element 1 12 Element 2 4 6 Element 3 3 2 Element 4 0 Element 5 1 HERIOT WATT UNIVERSITY 178 30 min 20 min TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 This time one simple loop replaces 6 lines of code i e Print element 0 Store 0 Print element 1 S
123. een as such Instead they use a form which is essentially a Visual BASIC window that is the interface between the user and the application and allows information to be input by the user or displayed to the user There may be more than one form in a Visual BASIC project Information may be input to a program via the keyboard or read directly from data files The program may also contain data that is assigned directly to variables or constants during execution time The output of information may be achieved through a variety of Visual BASIC control structures that are placed on the form at the design stage Output can also be directed to a printer or to an existing file Since file I O is beyond the scope of the Higher Computing course only the graphical methods will be discussed at this stage HERIOT WATT UNIVERSITY 87 88 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 The stages in writing a program in Visual BASIC involve the following aspects 1 Design stage the form is used to compose the graphical elements of the program Command buttons and other objects can be placed anywhere on the form and these will dictate how the application is to run 2 Setting properties the form itself and the objects it contains can have various properties set producing the visual effects required of the program Although there are numerous properties for each object the main ones would include Name of the object Colour Caption attached to ob
124. een built to process all outputs should be satisfactory extreme boundary testing data to test that the program functions properly with data at the extremes of its operation for example if a number entered is meant to be limited the program s performance is tested just within the limit on the limit and just beyond the limit as another example if a table is supposed to have a maximum number of elements the program is tested to see if it can cope with exactly the maximum and if it can cope when an attempt is made to exceed the maximum exceptions testing data that lie beyond the extremes of the program s normal operation these should include a selection of what might be called silly data to test the program s robustness that a user might enter in a moment of confusion or mischief Matching definitions Testing On the Web is a interactivity You should now complete this task Faults that become evident during testing are known as bugs If bugs are identified the program is sent back with the test logs to the programming team for debugging This process is likely to be iterative testing finds bugs they get fixed the program s tested again more bugs are found and so on It may be that bugs reveal flaws that were introduced at an earlier stage of the process at the design or even at the analysis stage If this is the case the documentation for each stage of the development process will need to be corrected 2 6 3
125. een them Because of the inexact way floating point numbers are stored in computers you should not use the equality operator between two real numbers Even if two real numbers are printed to the screen as the same two numbers this is no guarantee that they are the same internally The only way to test equality between real numbers A and B is to use the following expression If ABS A B lt small difference Then The function ABS returns the absolute value of any number ABS 5 3 gives 5 ABS 43 gives 43 Depending upon how accurate real numbers are held on the computer small difference is usually of the order 0 0000001 The relational operators are summarised in Table 6 6 These operations can be performed between most types of object but they will be used most often to compare two integer values or two characters Table 6 6 Relational Operators a less than amp lt a less than or equal to b gt a greater than or equal to b Example 1 Using a Relational Operator Problem How can a comparison be made between two variables Numi and Num to find out if Num1 is greater than or equal to Num2 Solution The comparison can be made using the relational operator gt e g Numi gt Num2 This comparison could be reversed to check if Num2 is less than Num1 e g HERIOT WATT UNIVERSITY 123 124 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Num2 lt Numi Example 2 Using a relational operato
126. em has to be worked out Data flow has to be identified at all stages The analyst schedules the work keeps an eye on performance and oversees the development of the system In respect of production a programmer s work is in two parts Second the programmers write the code test it and debug it though testing is often done by a separate team In most cases several programmers work together as a team under a senior programmer s supervision Programmers test a program by running it to ensure the instructions are correct and it produces the desired information If errors do occur the programmer must make the appropriate change and recheck the program until it produces the correct results This process is called debugging Programmers may continue to fix these problems throughout the life of a program HERIOT WATT UNIVERSITY 4 6 INDEPENDENT TEST GROUP 57 4 6 Independent Test Group Consider the following quote from a computing expert in the field of software development No no no no no who develop and implement code Should have absolutely no role Quite an adamant view with a clear message Programmers would be less inclined to test their software to destruction and take into effect test data that might cause unexpected results they have the knowledge of how the functionality of the code was designed and will test accordingly Also they probably don t have sufficient time to fully test the program under all
127. ems Machine code Native computer code that can be understood without translation Macro A block of code that automates a repetitive task Rather like a batch file they are normally created within an application then run by activating a key press combination or clicking on an icon maintainable software which is written and documented in a way which makes it easy for programmers to correct errors add new features or adapt the software Maintenance The upkeep of a program by repair and modification Methodology A technique involving various notations that enables the design of software to be implemented Module library A module library includes code for standard algorithms that can be re used by programmers Normal operation Running of a program under expected normal conditions Object A data item that can be manipulated by a computer system for example a database record or a file Object code The machine code produced by a compiler ready for execution by a processor Object oriented design A method that centres on objects and the operations that can be performed on them HERIOT WATT UNIVERSITY 236 GLOSSARY Object oriented language An object oriented computer language like Java that uses objects rather than actions and data rather than logic An object is represented by a class that can be extended to involve inheritance Optimised Refinement of code to make it more efficient Parameter An argument of a pr
128. en statement 1 else HERIOT WATT UNIVERSITY 6 14 COMPARISON OPERATORS 127 statement 2 end if This code means that when either Vone or Vtwo is equal to 6 then statement 1 is executed If both of the conditions are false then statement 1 is ignored and execution passes onto statement 2 Online there is an interactivity which you should attempt now Example 1 Wash the car Problem A program is written to prompt the user to enter two conditions a temperature and a weather forecast If either or both of the conditions are met then the program will display a suitable message to go and wash the car If no conditions are met the user will be informed that washing the car is not a good idea The conditions are compared to program constants The algorithm is shown below Solution 1 request a temperature from the user 2 request weather condition from user 3 if the first input gt 15 or the second input Sunny then 4 display Wash the car 5 else 6 display Not a good idea The Visual BASIC code for this program is shown in Code 14 Option Explicit Private Sub Command1_Click program using the OR operator 15th February 2004 Program by Fred Fink This program will prompt the user to enter a value and a condition Dim iTemp As Integer Dim weather As String iTemp InputBox Please input today s temperature weather InputBox Please input Sunny or Rainy If iTemp gt 15 Or weathe
129. entation testing documentation evaluation maintenance HERIOT WATT UNIVERSITY 2 3 THE ANALYSIS STAGE 15 Analysis is an attempt to understand a given problem clearly and exactly in order to generate a solution The outcome will QUESTIONNAIRES N a va loz NN be a specification that is used as the basis OBSERVATION for all subsequent work NS i DOCUMENT pamm Analysis sometimes called systems ANALYSIS E analysis is the job of a specialist person mer EXPERT SYSTEMS SYS the systems analyst re ane Full systems analysis has three phases 1 collection of information 2 analysis of information collected 3 production of a problem specification or user requirements specification Sometimes this stage begins with a vague idea or rough outline of the problem On other rather more formal occasions it will start with a full requirements specification This will include hardware and software specifications notes on project issues such as objectives constraints costs and schedule e It may also include a full functional specification which will describe exactly how the system is meant to behave The functional specification is what the development team will follow in creating the software system INTERVIEWS DISCUSSIONS OBSERVATIONS specification agreed beween client and developers HERIOT WATT UNIVERSITY
130. er 5 8 3 2 Answer 5 8 3 2 Answer 5 8 3 2 d Answer 5 8 3 2 Q2 Consider the following segment of programming code For x 1 to 3 For y 1 to 3 Sum x y Next y Next x Print Sum When run what would be the final value of the variable Sum Q OO 0 9 mm om BR ND Q3 Which one of the following statements represents a valid string assignment Name Bert Number 12345 Paper Scots man a b c d All of the above 6 1 Introduction In this topic you will be introduced to the Visual BASIC programming environment Variables and data types are discussed together with fundamental programming structures Formatted input and output constructs are described and exemplified using Visual BASIC code More advanced techniques involve conditional statements such as nested IF statements and the CASE construct Each Visual BASIC construct is exemplified using pseudocode and high level equivalent 6 2 The Programming Environment In this topic all language features are exemplified using Visual BASIC 6 Users of Visual BASIC NET should find few incompatible problems Important differences will be flagged where appropriate Visual BASIC 6 Visual BASIC is an event driven programming language that works within the graphical environment of Windows Visual BASIC code is associated with objects and each object has a set of events associated with it HERIOT WATT UNIVERSITY TOPIC 6
131. ers tools and techniques to design and implement a software solution HERIOT WATT UNIVERSITY 238 GLOSSARY Software development process A series of stages involving defined methods to produce a software project according to an initial specification Software engineering A sphere of computing where the emphasis is on the development of high quality cost effective software produced on schedule and within agreed costs Source code The code for a program written in a high level language This code is then translated into machine code Special purpose language Languages designed for specific tasks such as prolog for artificial intelligence or C for writing operating systems Specification A document outlining the program requirements set by the client SSADM Structured Analysis and Design Model An alternative to the waterfall model that deals only with the analysis and design phases of software development Standard algorithm An algorithm that appears over and over again in many programs Also called common algorithms Stepwise refinement Similar to top down design of sectioning a large and complex system into smaller and more easily manageable components Structure charts A diagrammatic method of designing a solution to solve a software problem Structured data Data that is organised in some way for example an array or database Structured listing Program listing clearly showing the modules involved complete with comment
132. erties of each control are then established HERIOT WATT UNIVERSITY 85 86 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 FT Properties C Sele Returns sets the text displayed in an object s title bar or below an object s Pressing function key F4 on an active button will open the Properties box as seen above Figure 6 2 shows five objects 3 control buttons a message box and a form Formi isual Basic is Figure 6 2 6 3 2 Attaching code to objects In the second process programming code is written for each event and attached to the appropriate object in the form The code for each event is written in the form of a sub procedure HERIOT WATT UNIVERSITY 6 3 BUILDING APPLICATIONS A sub procedure or sub program is a block of code that is implemented when an event such as a mouse click occurs Double clicking on any of the objects in a form or even the form itself will open up the program editor and reveal the code for each event For example clicking on the Exit button will display the code editor as follows FA Prajert1 Farm1 Cade Private Sub cmdExit_Click End End Sub All Visual BASIC code is written between the lines that Visual BASIC enters for you Private Sub cmdExit_Click End Sub On the right of the screen you can see a list of other events that are part of the Visual BASIC environment 6 3 3 Input and Output Controls Visual BASIC programs do not output to the computer scr
133. es an algorithm to find all occurrences of a particular word in a block of text or a spreadsheet package which uses an algorithm to find the maximum value in a range of cells These packages make use of standard algorithms and it is worthwhile for every programmer to know them When implemented these standard algorithms may become key components in a module library This section introduces 3 common algorithms used by programmers Namely 1 linear search 2 counting occurrences 3 finding maxima and minima You need to have prior understanding of arrays as examples given rely upon knowledge of accessing and manipulating such structures HERIOT WATT UNIVERSITY 8 5 STANDARD ALGORITHMS 217 8 5 1 Linear Search One task which computers frequently perform is to search through lists For example looking up a telephone number in a database finding and replacing a word in a text file or looking for a particular stock item in a warehouse etc Linear search is the simplest search method to implement and understand Starting with an array holding say 10 numbers with a pointer indicating the first item the user inputs the item being searched for which is known as the search key Scanning then takes place from left to right until the search key is found if it exists in the list Look at the list below RE Suppose the search key is 76 1 16 is compared to 76 Not the key so pointer moves on one place 2 9 is compared to the key N
134. et user input 2 format d o b and calculate age 3 display output As a structure diagram GET USER FORMAT D O B DISPLAY INPUT amp CALCULATE OUTPUT AGE Each of the three stages can be coded as a procedure sub program Implementation The coding for this would be as follows omitting details Private Sub cmdAge_Click comment lines Call Get_user_input Call Do_calculations Call Display_output End Sub Private Sub Get_user_input End Sub Private Sub Do_calculations End Sub Private Sub Display_output HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 199 End Sub Parameters As it stands this program could not work as data items cannot be transferred between the sub programs To be able to work we need a mechanism to transfer data items between the 3 sub programs This is achieved using parameters First think about the last procedure Display_output To do its work it needs to know the user s name the user s d o b the user s age These data items must be passed IN to this procedure We can show this on the structure diagram and the pseudocode AGE CALCULATOR DOC GET USER FORMAT D O B DISPLAY INPUT amp CALCULATE OUTPUT elz 1 get user input 2 do calculations 3 display output IN name dob age HERIOT WATT UNIVERSITY 200 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Next think about the middle procedure Do_calulations
135. etc As soon as you find that they do not match you can terminate the search as you know that the sequence is not a palindrome It is not necessary to continue searching the whole list of numbers as we know what we set out to find out Note that you only have to loop for count lt length 2 as you compare the first half of the array to the second half See following Figure 7 17 0 1 2 3 length 1 length compare 2 and 2 last 15 and last compare Figure 7 17 Comparing array elements for a palindrome A possible solution is shown in Code 31 Private Sub Commandi_Click program Palindrome 20th February 2004 gt Program by Fred Fink This program will test an input string for a palindrome Const sizeArray As Integer 30 Dim Palarray 1 To sizeArray As String Dim palindromeChar As String Dim length As Integer count As Integer Dim isPalindrome As Boolean count 1 Do While palindromeChar lt gt And count lt sizeArray palindromeChar InputBox Enter your characters one at a time Terminate by full stop Palarray count palindromeChar PicDisplay Print palindromeChar Output characters count count 1 Loop length count 1 gt to account for increment when is read in HERIOT WATT UNIVERSITY 188 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Now check for palindrome isPalindrome True count 1 Do While isPalindrome And count lt length 2 If Palarray count lt
136. evelopment team An error report is about a malfunction of the program and should contain details of the circumstances which lead to in the malfunction These error reports are used by the development team to find and correct the problem 2 6 4 Review questions Q16 Which one of the following statements describe alpha testing a Testing is done by the users b Testing is done within the organisation c Testing is done by specialist companies d Testing is done by the client Q17 Which of the following describes beta testing a The program is tested by the clients b The testing is more rigorous than alpha c The testing is for market research d The program is tested by specialist companies Q18 During alpha testing the program is usually subjected to exceptions testing This means a The input of unexpected data b The input of large numbers c The input of small numbers d All of these 2 7 The Documentation Stage Documentation is intended to describe a system and make it more easily understood Documentation will consist of 1 user guide 2 technical guide Some information may appear in both guides e g system specification Internal documentation such as remarks or comments in the code are for the benefit of the development team It will help if changes have to be made to the software in the future Other documentation for the development team includes all the documents produced in the software development
137. fTerms gt 0 And NoOfTerms lt 16 PicDisplay2 Print NoOfTerms First InputBox Enter first number Second InputBox Enter second number Third 0 Count 0 PicDisplay Print First Second Do Third First Second First Third Second Third Second PicDisplay Print First Second Count Count 1 Loop Until Count NoOfTerms 2 2 End Sub This file Fibonacci txt can be downloaded from the course web site Code 28 HERIOT WATT UNIVERSITY 170 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 The program input is restricted to values gt 0 and lt 17 using a DO Until loop for input validation If you find difficulty in following the logic of the program then perform a paper exercise running through the values of each variable as the program executes This is called a dry run and is best done by means of a trace table re Values First Loop First Loop Second C E 8 op If you have access to the on line version of SCHOLAR you will find it helpful to view the interactive version of this table which shows how it is built up line by line during a dry run of the code The two starting values are 1 1 which are assigned to variables First and Second Variable Third then takes on the value of First Second which is 2 First now takes on the value of Third to become 2 Finally the variable Second takes on the value of Third Second to become 3 The values of First and Second are now displayed to giv
138. g If Then and If Then Else statements nested Ifs and Elselfs are best avoided using Select Case 6 18 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY 144 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 HERIOT WATT UNIVERSITY Topic 7 High Level Language Constructs 2 Contents 7 1 Introduction 7 2 Fixed loops 7 2 1 The For Nextloop 7 2 2 Example 1 7 2 3 Example 2 7 3 Nested For loops Converting inches to centimetres Displaying integers using negative step 7 3 1 Use of an If statement with nested For Nextloop 7 4 Fixed Loop Exercises 7 5 Review Questions 7 6 Conditional Loops EET Do While l00p 2 3 4 4 ugg bo ae abana a we ake ee oe ew OSE SL 7 6 2 Example 1 7 6 3 Example 2 7 6 4 Example 3 Calculating a sum of positive integers Validating character input problem Range checking using a boolean variable 7 6 5 Do While Review Questions 7 6 6 Do Until LOOP 3 ate a ee ee a Oe a ae 7 6 7 Example 1 7 6 8 Example 2 Guessing an age with do until and nested else If Fibonacci numbers 7 6 9 Review Questions 7 7 Formatting output 7 8 Arrays 7 8 1 1 D Arrays 7 8 2 Declaring array
139. g relevant information to the project manager and other members of the consultancy team e deciding whether or not to go ahead with the project paying the consultants Sentence completion software development On the Web is an interactivity You should now complete this task 4 3 The Project Manager The project manager is responsible for the project The project manager will be appointed by the consultants The project manager supervises the project and carries out the initial stages If it goes ahead the project manager will take charge of the project from the first brainstorming session to the software launch and implementation It s up to the project manager to keep the process on schedule by whatever means possible Sometimes it may involve cracking the whip to make sure the work is up to standard and that important deadlines are met being a project manager means being accountable for the entire duration of the project HERIOT WATT UNIVERSITY 51 52 TOPIC 4 PERSONNEL Project managers are easy targets for criticism because the success or failure of a project is often dependent on their decisions Hence it can be a thankless task at times for this overworked person The most time consuming undertaking of all will be managing people whether they be clients or as members of the consultancy team With clients the project manager needs to extract all the relevant information from the client and force
140. ges to identify and remove the errors in the source code Some compilers assist by adding line numbers to the source listing to help pinpoint errors and all compilers will describe the nature of the error e g missing semi colon expected keyword etc although interpreting some compiler diagnostics is a skill in itself Ease of use Interpreters however are more suitable for beginners to programming since errors are immediately displayed corrected by the user until the program is able to be executed On the whole compilers tend to be more difficult to use Portability A compiler produces a complete machine code program which can be save copied distributed and run on any computer which has the appropriate processor type An interpreter does not do this The machine code has to be generated each time the program is run This means that the interpreter must always be present and program execution is slower HERIOT WATT UNIVERSITY 79 80 TOPIC 5 LANGUAGES AND ENVIRONMENTS 5 9 3 Review Questions Q13 One of the main differences between a compiler and interpreter is a An interpreter is faster then a compiler b Acompiler is better for beginners c Acompiler creates an independent machine code program d An interpreter is much harder to use Q14 One disadvantage of using an interpreter is a Looping structures have to be interpreted each time they are entered b It stops execution when an error is encountered c
141. gure 7 7 Running total program Code run and test the progam above HERIOT WATT UNIVERSITY 162 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 7 6 3 Example 2 Validating character input problem A program is written to prompt the user to enter a character The program continues to prompt until it receives a character other than a Y or a y Solution The algorithm is shown below display Continue get input from the keyboard do while user enters Y or user enters y display Continue get input from the keyboard loop display Out of loop NOON amp WN BF The Visual BASIC program is shown in Code 25 Option Explicit Private Sub Command1_Click 17th February 2004 Program by Fred Fink gt This program will illustrate the Do While loop gt Program CharEntry gt This program prompts the user to enter a character It uses a WHILE loop to repeatedly check that a character other than a Y or a y has been entered Dim Response As String PicDisplay Print Do you want to continue Response InputBox Y or y Do While Response Y Or Response y Response InputBox Continue Loop PicDisplay Print Out of loop End Sub This file Validate txt can be downloaded from the course web site Code 25 The program output is minimal since it only responds to the correct input then the program will simply accept the character that is entered Only when the incorrect
142. he full Visual BASIC program is shown in Code 18 Option Explicit Private Sub Commandi_Click Use of the Case Select statement 15th February 2004 gt Program by Fred Fink This program will prompt the user to enter a date gt and the month will be output HERIOT WATT UNIVERSITY 140 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Dim iMark As Integer iMark InputBox Please input a test mark Select Case iMark Case 85 To 100 PicDisplay Print iMark grade A Case 65 To 84 PicDisplay Print iMark grade B Case 50 To 64 PicDisplay Print iMark grade C Case 30 To 49 PicDisplay Print iMark Case 0 To 29 PicDisplay Print iMark Case Else PicDisplay Print iMark is out of range Try again End Select End Sub grade D grade E Private Sub cmd_Exit_Click End End Sub This file Case2 txt can be downloaded from the course web site Code 18 Program output is shown in Figure 6 18 Form1 ML E3 115 is out of range Try again 99 gade 68 gade B 50 gade C 49 gade D 15 gadeE 10 is out of range Try again Figure 6 18 HERIOT WATT UNIVERSITY 6 16 THE SELECT CASE STATEMENT 141 6 16 3 Select Case Example 3 Example 3 Extending the testing for a weekend or weekday using text Input Problem Write a program to test whether a string variable Day holds text that represents a week day or a weekend Assume input can be in either lower or upper case Solution
143. he program from compiling The program cannot run Run time Errors These are errors detected during the execution of the program Even given that a program is translated into machine code and runs on the computer there is no guarantee that it will not generate errors For example a common mistake made by programmers is to divide by zero In most cases this will produce a run time error and cause the program to halt unexpectedly Another example includes attempting to read character data directly as numeric Array Bounds Exceeded is a common mistake in languages which support array data structures Here the programmer is attempting to access a position within the array which exceeds its predefined bounds Logical Errors These are errors in the design of the program e g calling the wrong procedure or routine Even given that the program translates to machine code and does not halt unexpectedly due to run time errors there is no guarantee that it will not fail It may contain logical errors These are errors in the logic of the code itself For example writing code to add two numbers instead of multiplying them or forgetting to write code to do something when a condition that is being tested fails HERIOT WATT UNIVERSITY 3 6 SUMMARY 47 Other examples include making a call to the wrong module passing incorrect data into a module passing the wrong data out of a module Error types Online there is an inte
144. hes Tab 12 Centimetres PicDisplay Print For Inches 0 To 50 Step 5 Cms Inches 2 54 PicDisplay Print Tab 5 Inches Tab 15 Cms Next Inches End Sub Code 20 The program output is shown in Figure 7 2 For Next Inches Centimeteres D 0 5 12 7 10 25 4 15 38 1 50 8 63 5 76 2 88 9 101 6 114 3 127 Figure 7 2 Note that the output of this program is in tabular form This was achieved using the TAB function first to output the heading then the results Tab is short for tabulate and HERIOT WATT UNIVERSITY 7 2 FIXED LOOPS 151 the output items are separated by the values within the tab statements If the value of step is not specified it is assumed by Visual BASIC to be the value 1 by default Conversion program 1 Code and test the conversion program 2 Adapt it to convert miles to kilometres use 1 mile 1 609 km 7 2 3 Example 2 Displaying integers using negative step Problem Write a program that will output ASCII codes from 100 to 65 together with the corresponding characters that the numbers represent Use a for next loop with ve step and output the results in tabular form Solution display The ASCII codes from 100 to 65 for counter 100 to 65 step 1 display the value of the integer and character next counter PWN FE The Visual BASIC program is shown in Code 21 Option Explicit Private Sub Commandi_Click 16th February 2004 gt Program by Fred Fink
145. hes must be week days Note Here you are comparing with the single character and not the entire string called Day so single quotes are required to show that you are using a character In order to test the first character of the string Day the Visual BASIC in built function Left is used For example Left Monday 1 would produce the character M 6 16 4 Select Case Summary Sentence completion case statement On the Web is an interactivity You should now complete this task Musical Notes A B C D E F and G are valid musical notes Write a program that allows the user to input a character and uses a CASE statement to test and display if the character is a valid musical note HERIOT WATT UNIVERSITY 6 17 SUMMARY 143 6 17 Summary an Input Box or text box can be used to get user input to a program output can be directed to a Message box or to the form output can be formatted using TAB and SPC functions variables must be declared before use name and type undeclared variant type should be avoided variable types include integer real single or double Boolean string string concatenation is implemented using the amp character the scope of a variable defines where it can be accessed from wherever possible local variables should be used rather than global variables operator precedence must be considered carefully when evaluating complex expressions selection constructs are implemented usin
146. hes to emphasise or that a particular developer prefers HERIOT WATT UNIVERSITY 2 2 THE NEED FOR ITERATION In this course we will consider the following stages analysis documentation The idea here is that the development of the system flows down or cascades through the stages like water flowing down a fall As each stage is completed responsibility and control is passed down until the final section is completed The process as it stands represents an ideal world rather than reality Developers do not know everything the client will need at the start of a project they make wrong decisions possibly based on incomplete information The model can be improved significantly if it is made to be iterative Ideally you would start a process with the analysis and work through the stages in turn doing everything only once In practice this happens rarely People make mistakes faults become apparent that can only be corrected by going back to an earlier stage of the process An iterative development model There is an on line illustration of the need to use an iterative development model You should view this animation now 2 2 1 Review questions Q4 Which one of the following statements regarding the order of the stages in the software development process is correct Design implementation testing documentation Analysis testing implementation design Design testing evaluation implementation Analysis
147. him her to make decisions regarding software specification With his her own team the project manager promotes good welfare by raising team spirit through regular personal meetings and positive appraisal A job description for a typical project manager might involve the following requirements have experience in dealing with a variety of clients Se Amr e the ability to manage a team BENEFITS foment Ieee Salary 40 50k html possess excellent verbal and written bR communication skills z nds on position where the PM will sonally contribute to the k 2 H0 0 YIJVNYW 193rO0Hd have strong attention to detail possess the ability to create schedules and budgets e show remarkable endurance under stress 4 4 The Systems Analyst The systems analyst carries out the system investigation In large systems the analysis might be carried out by a team of analysts The systems analyst is appointed by the project manager Systems analysts are active in the analysis design testing and implementation phases of the project Systems analysts will usually have some programming experience but they won t necessarily be programmers The aim of the systems analyst is to produce a clear specification that the rest of the development team will use in the subsequent stages Analysts begin an assignment by discussing the systems requirements with the client HERIOT WATT UNIVERSITY 4 4 THE SYSTEMS ANALYST 53 an
148. hould be accepted Answers from page 44 Q10 a Q11 b Q12 c Q13 a To determine that the system meets the specification Output statements at key points in the code Design input routines that will not crash when presented with unexpected data gt wr ae Ta They could remain hidden until the program is run under all conditions HERIOT WATT UNIVERSITY 246 ANSWERS TOPIC 4 4 Personnel Answers from page 55 Q1 Q2 Q3 Q4 Q5 c The group who will purchase the software d Benefit the organisation in some way d The systems analyst is responsible for the entire project a Allow the systems analyst to produce a clear specification of the problem b The project manager Answers from page 58 Q6 Q7 Q8 Q9 d All of the above a They report directly to the project manager at all stages of programming b Programmers will tend to test only within the functionality of their own code d The project manager Q10 c Testing is done by external groups on a variety of computer platforms HERIOT WATT UNIVERSITY ANSWERS TOPIC 5 247 5 Languages and Environments Revision page 63 Q1 dj all of the above Q2 b compiler produces object code for a whole program in one operation Q3 d Syntax error Answers from page 68 Q4 b languages have to be adapted so new versions are released Q5 c BASIC Algol Pascal Comal Q6 d Moderation Q7 c Vi
149. iew Questions Q4 Which one of the following variable names would not be allowed in Visual BASIC a Hello b Number_1 c 17 5 Vat d SCHOLAR Q5 The choice of a meaningful variable name in programming is very important because a It makes it easier for programmers to locate and fix errors b It makes the programs more efficient c Meaningful variable names make the program more reliable d All of the above Q6 A program is written to input a person s age in years and calculate how old they will be in 10 years time Which of the following data types would be required in the program to hold the person s age a String b Real c Boolean d Integer Q7 A program is designed to generate prime numbers up to the maximum value possible with precision The results are stored in a variable called prime In order to perform the calculation the variable prime would need to be declared as Integer Real double Integer long a b c d Real single HERIOT WATT UNIVERSITY 99 100 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 6 7 Declaring Variables Within Visual BASIC variables are used to represent and identify values within a program The values are held in temporary storage locations in the computers memory Each memory location is identified by a unique variable name and the value of its contents can change during the execution of a program Once the program has ended variables will be reset
150. iew this topic HERIOT WATT UNIVERSITY Topic 2 Features of Software Development Process Contents 2 1 Introduction 2 2 The need for iteration 2 2 1 Review questions 2 3 The Analysis Stage 2 4 The Design Stage 2 4 1 Review questions 2 4 2 Designing the human computer interface 2 4 8 Designing Data Structures 2 4 4 Other design choices 2 5 The Implementation Stage 2 5 1 Debugging 2 5 2 Standard algorithms and module libraries 2 5 3 Review questions 2 6 Testing 2 6 1 Test data preparation 262 Alpha testing sae a he We a a eue de te dada amp tete ne Gee 2 6 3 Betatesting s 2 aed bop pp AP eda are eM doe ao oy 2 6 4 Review questions 2 7 The Documentation Stage 2 7 1 User guide 2 7 2 Technical guide 2 8 Evaluation 2 8 1 Robustness and reliability 2 8 2 Review questions 2 9 Maintenance 2 10 Weaknesses of the software development process 2 11 Summary 2 12 End of topic test 11 12 13 14 16 17
151. ike 99s oP WN BE The full Visual BASIC code for this program is as follows Option Explicit Private Sub cmdExecute_Click program simple If_Then 13th February 2004 gt Program by Fred Fink A program to show a simple if then statement Const Ice As Integer 99 Dim userno As Integer userno InputBox Give me a number HERIOT WATT UNIVERSITY 118 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 If userno Ice Then PicDisplay Print I like Ice s End If PicDisplay Print Program End End Sub Code 11 In this program input is via an InputBox and output by means of the PictureBox function Although a PictureBox is meant for graphics it can deal with text as well and this somewhat tidier than displaying text on a form The PictureBox property is set to the name PicDisplay in the properties window Program output is seen in Figure 6 10 Form like Ss rogram End Figure 6 10 Practical Examples using If Then Several examples are given here that use comparison operators and if constructs within a program to solve a problem Try writing the programs for yourself and experiment with making changes to the code to ensure you understand what is happening Example 1 Calculating the area and circumference of a circle Problem Write a program that calculates the area and circumference of a circle The calculations should only be performed if the radius is positive i e a valid radius So
152. ility e efficiency HERIOT WATT UNIVERSITY 30 Eo La TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS e maintainability and from Int2 level e readability e fitness for purpose and e quality of HCI Sentence completion Evaluation On the Web is an interactivity You should now complete this task Evaluation terminology On the Web is an interactivity You should now complete this task 2 8 1 Robustness and reliability There is often confusion between the terms robustness and reliability A program is robust if it can cope with problems that come from outside and are not of its own making e g corrupt input data Reliability is an internal matter A program is reliable if it runs well and is never brought to a halt by a design flaw When the program is complicated the distinction between the two terms is not always clear When a machine hangs it is not always obvious whether this is due to a failure in robustness or reliability Robustness The designer should try to ensure that the design is robust the resulting software should be able to cope with mistakes that users might make or unexpected conditions that might occur These should not lead to wrong results or cause the program to hang As examples of an unexpected condition we could take something going wrong with a printer it jams or it runs out of paper or a disc drive not being available for writing because it simply isn t there the user s forgot
153. im temp As Integer Display Print Numbers before swap Tab 25 valuet value2 temp valuel valuei value2 value2 temp BlankLines 1 Display Print Numbers after swap Tab 25 valuel value2 End Sub Private Sub GetNumbers ByRef Numi As Integer ByRef Num2 As Integer Numi InputBox Input first value Num2 InputBox Input second value End Sub Private Sub cmd_Exit_Click End End Sub This file RefParameter txt can be downloaded from the course web site Code 35 The first call of procedure GetNumbers produces the values for formal parameters Num1 HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 211 and Num2 through user input These values are passed to the actual parameters Number 1 and Number2 BlankLines 2 produces two clear lines before output of results The values are now swapped temp 20 valuei 40 value2 temp Notice the procedure BlankLines 1 is nested within procedure GetNumbers Results are displayed via procedure GetNumbers Typical output is shown in Figure 8 3 Numbers before swap 20 40 Numbers after swap 40 20 Figure 8 3 8 2 1 8 Review Questions Q8 The use of procedures in a program offers many advantages to the programmer Which one of the following would represent such an advantage a They must have meaningful names b Repetition of lines of code are avoided c Procedures can be nested within procedures d They can work
154. imum List End Sub Private Sub Setup Initialise variables Randomize gt and clear output boxes PicList Cls HERIOT WATT UNIVERSITY 8 5 STANDARD ALGORITHMS 225 PicResult Cls PicList Print Pointer 0 Maximum 0 End Sub Private Sub Populate_List ByRef List Fill array with Dim Fill As Integer 716 random numbers For Fill 0 To 15 List Fill Int 100 Rnd 1 PicList Print List Fill Next Fill End Sub Private Sub Search_for_max ByVal Pointer ByVal Maximum ByRef List Maximum List Pointer Do Pointer Pointer 1 If Maximum lt List Pointer Then find maximum Maximum List Pointer End If Loop Until Pointer gt 14 PicResult Print The maximum value in the list is Maximum End Sub Private Sub Command2_Click End End Sub This file Maximum txt can be downloaded from the course web site Maximum 84 41 22 64 53 36 53 47 95 56 76 55 72 48 59 59 The maximum value in the listis 95 End Program HERIOT WATT UNIVERSITY 226 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS 8 5 5 Finding minimum Finding the minimum is almost exactly the same as finding the maximum only 1 line of code needs to be changed in the algorithm although for readability you will want to change the variable name maximum to minimum Program to Find Minimum 1 Rewrite the algorithm form the previous page for Finding a Minimum 2 Adapt the coding to match 3 Test your new program
155. in Downloading web based content from a remote site to a user s local machine can include animations graphics MP3 audio files video clips and so on and this is authenticated by the scripting language However be warned Executable code can inadvertently be downloaded from a remote server to a web browser s machine installed and run using the local browser s interpreter This is easily done by visiting dubious web sites or downloading programs without valid authenticity The user is probably unaware of anything devious occurring This is a weakness in the formal rules defining scripting languages like JavaScript and VBScript 5 7 4 Creating a Macro A macro is a way to automate a task that you perform repeatedly or on a regular basis It is a series of commands and actions that can be stored and run whenever you need to perform the task Instructions can be simple such as entering text and formatting it or complex like automating tasks that would take several minutes to do manually Macro contents consist of ASCII text and can be created and edited in any simple text editor Many programs like Microsoft Word and Microsoft Excel can create macros easily All you have to do is record a set of actions as you perform them For example you could record opening a new document using a specific template inserting a header and inserting a name and address and greeting Each time you replayed the macro HERIOT WATT UNIVERSITY 75 76 T
156. ion HERIOT WATT UNIVERSITY 3 2 DESIGN METHODOLOGIES AND NOTATIONS DIFFICULT PROBLEM 4 Less difficult Less difficult Fairly Easy Easy Problem Problem Problem Problem Easy Fairly Easy Problem Problem 5 Easy Easy Easy Fairly Easy Problem Problem Problem Problem Easy Easy Problem Problem Easy Easy Easy Problem Problem Problem Figure 3 1 Stepwise refinement Stepwise refinement allows the designer to concentrate on one small part of the problem at a time If thinking about the problem as a whole the designer does not have to bother with details In thinking about a portion of the detailed design the designer does not have to bear in mind all the rest of the problem This makes the process manageable Once manageable parts have been identified the analyst can assign individual tasks to different teams of programmers The complex task is made more straightforward by the system of divide and conquer Programmers often use stubs when using a top down technique A stub is an outline of a module that does little more at run time than declare its presence or return a value of appropriate type When all the stubs are in place the program as it stands can be tested to make sure that all the stubs are properly linked Then the detailed work can begin Advantages of top down design On the Web is an interactivity You should now complete this task HERIOT WATT UNIVERSITY 39 40 TOPIC 3 TOOLS AND T
157. ions and Procedures 8 5 Standard Algorithms 8 5 1 Emea Search a ass 404 eet 2 Rae ae R arte 8 5 2 Linear Search Examples 8 5 3 Counting Occurrences 8 5 4 Finding Maximum 8 5 5 Finding minimum 8 6 Further activities on Standard Algorithms BE SUMIMANY eect ala te A ds as aL Rh ae ter deter a E E et ewe Jane te So Gana eed 8 8 End of topic test sels se es aa nine ea ee ee ae ken a we SSS See Prerequisite knowledge Before studying this topic you should be able to e describe and exemplify pre defined functions e recognise appropriate use of the following standard algorithms input validation find min max count occurrences linear search Learning Objectives After completing this topic you should be able to 193 194 196 212 213 213 214 215 216 217 217 221 223 226 226 226 227 191 192 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS understand and use procedures in programs e understand and use functions and user defined functions in programs e describe how the use of procedures and functions aids modularity of programs understand parameters and how they are passed in out in out understand parameter call by value and call by reference e be able to describe in pseudocode and implement
158. is done in a graphical environment Users can click on various objects where each object is programmed independently to be able to respond to user actions A Visual Basic program is therefore modular being made up of many subprograms each having its own program code that can be executed independently 8 2 Procedures and Functions Procedures and functions provide a means of producing structured programs not only in Visual BASIC but in other programming languages as well Procedures and functions allow a program to be broken up into into more meaningful and logical sections Advantages of modular programming The repetition of lines of code is avoided Rather than repeating the same operations several times in a program the code can be placed in a procedure or function The procedure is then called as many times as necessary without re writing the code It allows testing of the procedure code to take place in isolation from the main program Each functional unit can be written independently by programming teams making this part of the software development process more efficient Debugging of the main body of the program is simplified since each procedure can be individually tested Procedure code can be saved and re used in future projects Module libraries HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 195 for instance are repositories for useful chunks of code that can be accessed by programmers who could save time b
159. ist Pointer SearchKey Then Found True PicResult Print Search item SearchKey found at position Pointer Else Pointer Pointer 1 End If Loop If Not Found Then PicResult Print Search item SearchKey is not in list End If End Sub Private Sub Command2_Click End End Sub This file Linear txt can be downloaded from the course web site Code 37 HERIOT WATT UNIVERSITY 220 m 30 min TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Linear Search 2 61 30 82 90 38 79 26 13 39 95 35 35 48 68 49 23 Search item 68 found at position 14 Figure 8 5 The linear search is not the most efficient search strategy since each array element has to be compared with search key until a match is found For example for an array holding 1000 items on average 500 comparisons will be made before the key is found If the data items are sorted into order however then the search time can be improved using a more complex algorithm called binary search This is covered at Advanced Higher level Despite the large number of comparisons required to find an entry it is probably the fastest technique for small arrays It is also the most simplistic in terms of coding It may also be the only method to search larger unordered tables of data Coding linear search 1 Code the example above 2 Test that it works for a comprehensive range of data 3 Store it in a module library for later use Sear
160. it is x appropriate to use a function or a procedure with parameters HERIOT WATT UNIVERSITY 216 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS 8 5 Standard Algorithms An algorithm is a finite sequence of steps which when followed will accomplish a particular task The term algorithm derives from the name of the mathematician Mohammed ibn Musa al Khwarizmi c 825AD who was a mathematician and part of the royal court in Baghdad Al Khwarizmi s work is the likely source for the word algebra as well Figure 8 4 Cunieform tablet There is ample proof that the use of algorithms was evident around 2000 3000 BC by the ancient Sumerians whose work was inscribed on clay tablets using a cunieform cipher Translating this text revealed mathematical rules and astronomical data written in sexagesimal notation base 60 from which remains 360 degrees for circular measure 60 minutes per hour 60 seconds per minute and so on A computer program can be viewed as an elaborate algorithm In mathematics and computer science an algorithm usually means a procedure that solves a problem One major objective of this topic is to introduce you to common algorithms that have been tried and tested by programmers with knowledge of good algorithm design Many algorithms appear over and over again in program after program These are called standard algorithms or common algorithms Think about a word processing package which us
161. itrti loop You should obtain a value of 210 for the sum of all numbers between 0 and 20 inclusive HERIOT WATT UNIVERSITY ANSWERS TOPIC 7 Answers from page 171 Q12 Q13 c The loop need not be entered if the condition fails at the start a Q14 b 12345 b d Selection Q15 Q16 1 Any one of the above Indexing arrays page 178 Q17 c array 0 3 0 0 Q18 d array 7 3 0 0 Q19 c 2 Q20 a 3 Q21 c array 8 12 5 19 3 0 7 52 Q22 c array 8 23 5 9 3 4 7 52 Q23 array 0 9 3 0 Q24 array 0 7 0 0 6 0 0 3 2 0 Q25 The program fragment which will help you to do this is for i 0 to 9 myarray i Answers from page 180 Q26 d All of the above options Q27 b A for loop d Q28 d 046257 Q29 a value_1 0 Hello b 10 Q30 Heads and Tails Program page 185 The full Visual BASIC program is shown in Code 38 Option Explicit HERIOT WATT UNIVERSITY 251 252 ANSWERS TOPIC 7 Dim HeadsTails 1 To 1000 As Integer Private Sub Commandi_Click 220th February gt Program by Fred Fink gt This program simulates the tossing of a coin Dim toss As Integer heads As Integer tails As Integer Dim count As Integer Randomize PicHeads Cls PicTails Cls PicTosses Cls count InputBox Enter number of tosses For toss 0 To count 1 HeadsTails toss Int 2 Rnd 1 Generate numbers Next toss For toss 0
162. ject Height width Font used Position of object within the form Border style Properties are changed by highlighting the object and pressing function key F4 This opens up the Properties window from which changes can be made 3 Coding stage code is designed and written for each object and when the main program is run each event will become part of the overall effect Example events would include e Clicking a command button Loading a form e Clearing the contents of a text box Ending a program When Visual BASIC is started Form shows by default You will see exemplar programs that make use of the following Visual BASIC constructs later in this topic and others 6 3 4 Input Methods In Visual BASIC there are many ways of inputting data We will only consider two of these e using the InputBox function e using Text Boxes on the form HERIOT WATT UNIVERSITY 6 3 BUILDING APPLICATIONS 89 6 3 4 1 InputBox function A program may ask for user input during its execution This can be accomplished using the InputBox function which by default allows text entry The full syntax for the InputBox function is InputBox Prompt Title xpos ypos Prompt is the displayed message Title is the optional text that will appear in the title bar xpos ypos coordinates for positioning the InputBox on the screen For example a program may require the user to enter a name The format is Name InputB
163. le tossing a coin random values 1 for heads or 2 for tails throwing a die random values between 1 and 6 roulette random values between 0 and 49 Random numbers Visual BASIC has a built in function RND that produces a random number from 0 to 1 The randomise function allows the RND function to start from a seed value and to produce a series of numbers based on the seed Random numbers are generated internally using the computer s internal clock Since the random values produced are real they must be converted into integers before being stored in the array This can be achieved using another function INT Values are rounded down to the nearest integer For example Int 7 3 7 Int 6 8 7 7 8 7 Simulation of tossing a coin Problem Write a program to simulate the tossing of a coin up to1000 times determined by the user and output the number of heads and tails produced The program can be done in several sections 1 Generate random numbers within the range 2 Store results of up to 1000 tosses 3 Display output The following code segment will generate the random numbers and convert them to integers within the range 1 and 2 Randomise for toss 0 to 999 HeadTails toss Int rnd 2 next toss HERIOT WATT UNIVERSITY 7 8 ARRAYS 185 This will fill the array called HeadsTails with either 1s or 2s Counting heads and tails With 1000 numbers stored we can now scan the array and count the occurrence
164. les any computer to run Java programs Client The person or group that initiates the development process by specifying a problem Compiler A program that translates a complete high level language program into an independent machine code program Concatenation Joining of Visual BASIC string variables to make longer strings using the amp operator HERIOT WATT UNIVERSITY 232 GLOSSARY Conditional loop A control construct which allows a block of code to be repeated the number of repeats is not known in advance by the programmer but depends on a condition which may be true or false often depending on user input Conditional loops These loops test for a condition after each iteration before performing a further loop Corrective maintenance Correction of previously undetected errors during development that is now apparent after installation of the software on the client site COTS Commercial Off The Shelf software An alternative software development system that allows programmers to purchase ready made software Can be an expensive option Data Unstructured information A collection of numeric or alphanumeric characters which can be processed by a computer Raw data is meaningless to people Database An organised and structured collection of related data Data modelling A process used in object oriented languages that identifies objects how they relate to one another and their manipulation Debugging The detectio
165. lets into the script 9 10 11 12 13 14 15 Pop up Calander 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Cancel c Validating the content of fields When filling in forms each field especially required fields denoted by an asterisk are validated for correct input If the field is left blank or incorrect information entered then a user message will be generated and you may not continue HERIOT WATT UNIVERSITY 5 7 SCRIPTING LANGUAGES Please provide the following details This is necessary in case we need to contact you regarding delivery of your order Title First Name LastName Email Address __ Phone Number _ If you would like your order delivered to someone other than yourself please enter their contact details below Title FirstName _ E Last Name 5 7 3 The need for scripting languages Nowadays scripting languages are becoming more popular due to the emergence of web based applications The market for producing dynamic web content is now expanding extremely rapidly so new scripting languages have been developed to allow users with little or no programming expertise to develop interactive web pages with minimum effort Also the increases in computer performance over the past few years has promoted a comparable increase in the power and sophistication of scripting languages that unlike conventional programming languages can even have certain security features built
166. lution In the previous topic an example was given for calculating the circumference of a circle using a constant for the value of pi This example could be modified to use an if statement to validate the radius i e HERIOT WATT UNIVERSITY 6 13 THE IF THEN ELSE STATEMENT 118 if radius gt O then do calculations display results Example 2 Write a program to input numbers from the keyboard and to print them out The program terminates when 1 is entered A suitable message should be output input number if number gt 0 output number end terminate program output message 6 13 The If Then Else Statement So far we have shown you the use of the if then statement when there is only one alternative i e if the expression is true then execute a single code fragment If the expression is not true you may want to execute a different code fragment This is known as an If Then Else statement and the general format is if condition then statements 1 else statements 2 End if Again the statements may be single or they can be multiple statements if expression TRUE FALSE statements 1 statements 2 rest of program If the expression is true then the code fragment following the then statements 1 will be executed If the expression is false the statements following the else statements 2 will be executed HERIOT WATT UNIVERSITY 120 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Ex
167. ly by putting relevant information on the screen Finally add a section to the above program which will print the array in reverse order after it has printed it conventionally Indexing arrays Answer the following questions Use the arrays interaction on the course web site to help you find out the answers HERIOT WATT UNIVERSITY 7 8 ARRAYS 179 Q17 Begin with an array of 4 elements with a subscript range of 0 3 All values are initialised to O i e array 0 0 0 0 Set array 1 3 What are the arrays contents a array 0 0 0 0 b array 3 0 0 0 c array 0 3 0 0 d array 0 0 3 0 e array 0 0 0 3 f none of the above Q18 Using the same array set array 0 7 What are the array contents now a array 0 0 0 0 b array 3 7 0 0 c array 8 0 7 0 d array 7 3 0 0 e array 0 3 7 0 f array 7 0 3 0 g array 0 7 3 0 h array 0 7 0 3 i array 0 0 7 3 a iagt Q19 Set up a 4 element array with a subscript range of 0 3 with the following values array 3 6 2 8 What is the value of array 2 3 6 2 Q O 0 9 8 e none of the above Q20 In the same array as the previous question what is the value of the element with index 0 Q O 0 D x x n wa D OO e none of the above Q21 Set up an 8 element array with a subscript range of 0 7 e g array 8 23 5 19 3 0 7 52 N
168. member You can think of a few more for yourself Clearly these algorithms HERIOT WATT UNIVERSITY 224 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS are extremely useful and very widely used To find a maximum we set up a variable which will hold the value of the largest item that has been found so far usually the first data element If an element in the array exceeds this working maximum update the working maximum that value Such algorithms sometimes have to return the index number of the largest or smallest element and sometimes the actual maximum or minimum value The algorithms to return the maximum and minimum values are shown below Finding the maximum O OO TF WN BE set pointer to zero set maximum to first item in list Do increment pointer compare maximum to item at current position if item gt maximum then set maximum to item Loop until end of list report maximum value Online there is an interactivity you should attempt now The full Visual BASIC program for maximum is shown below Option Explicit Dim SearchKey As Integer Pointer As Integer Fill As Integer Dim Maximum As Integer Dim List 15 As Variant Private Sub Command1_Click gt Program Maximum 29th February 2004 gt Program by Fred Fink gt This program will perform a search on an array holding 16 random integers and output the maximum value Setup Call procedures Populate_List List Search_for_max Pointer Max
169. n location and removal of errors in a program Declarative language Programmers use this type of language to specify what the problem is rather than how to solve it by writing code The language uses facts and rules to express relationships Desk checking Akin to a dry run where the running of a program is checked without a computer Development team Generic description of the personnel involved in developing the software solution Dry run A pen and paper exercise to debug a program efficient an efficient program is one which does not make unnecessary demands on processor time memory or other system resourses HERIOT WATT UNIVERSITY GLOSSARY 233 Event driven A system that responds to an external event such as mouse click or a key press Event driven language An event driven language that is designed to handle external events like interrupts mouse clicks etc Exceptions testing Testing the robustness of a program by entering silly data character data instead of numeric data excessive values etc Executable code Independent machine code that can be run without translation Exhaustive testing Complete testing of a program under every conceivable condition An expensive method time wise Explicit declaration Each variable for example is declared unambiguously by the user so there is much less room for error in running programs Visual BASIC Feedback A looping system where information is fed back in to a computer s
170. n a file All of the above a b c d Q7 What shape will be displayed by the following Visual BASIC program fragment for any value of N gt 1 for i 1 to N for j 1 toi print next j print next i Triangle Square Rectangle a b c d Circle Q8 What will be displayed by the following Visual BASIC program fragment assuming N 3 sum 0 for i 1 to N for j 1 to N sum sum j next next i print sum a 16 b 17 c 18 d 19 HERIOT WATT UNIVERSITY 7 6 CONDITIONAL LOOPS 159 7 6 Conditional Loops With the for next loop the number of iterations must be known in advance so that the counter variable can be set There are many occasions in programming where the number of iterations is unknown so an alternative looping structure has to be used The Do Loop is a viable alternative to the for next statement In Visual BASIC Do loops come in a variety of flavours and for any given program there will probably be more than one solution using a Do 1loop variant There are two main do loop constructs with two variants 1 Do While loop and variant Do loop While 2 Do Until loop and variant Do loop Until 7 6 1 Do While loop The do while loop repeats a given set of instructions while a given condition is true The general form of this statement is Do while test condition statements Loop The loop repeats itself until the condition becomes false
171. nally three standard algorithms required for Higher Software Development are discussed with exemplar code for each supplied You will recall from Topic 3 that an important aspect of the design phase was the idea of refining a complex program by progressively breaking it down into smaller easier to solve units top down design with step wise refinement Each of these units called modules or program blocks can be independently coded in a high level language and then amalgamated to form the complete program The use of structure charts emphasise this modular design and also the relationship between all the modules in the software system HERIOT WATT UNIVERSITY 193 194 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Produce Best Solution Neue ormatted QuIAU Output In comparison to commercial software the programs that you will be writing in Visual Basic will be relatively short and you might not see the need to use modular techniques The Windows operating system for example contains well over 30 million lines of code Just think of trying to program this in one large block of code This would be an impossible task without the system being decomposed into many smaller discrete units that can be easily modified and more readily debugged and compiled Your own programs however small they may be should embody the principles of modularity Visual Basic is an event driven programming language where the programming
172. ncing a Alteration in the flow of control based upon the test of a condition b The repetitive execution of a sequence of instructions c The execution of program statements in order from beginning to end d Exiting a loop structure after a sequence of instructions Q20 Which one of the following expressions represents the logical AND operator a Requires only one condition to be tested b The expression is TRUE when both conditions being tested are TRUE c The expression is TRUE if either the conditions being tested are TRUE d Can be used to test for values outwith a given range Q21 Which one of the following is NOT a control structure in programming Sequence Repetition Assignment a b c d Selection Outwith range When does the following statement evaluate to be TRUE ig number lt 0 or number gt 9 HERIOT WATT UNIVERSITY 130 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 6 15 Other Forms of If Statement Other more complex variations on the If Statement are possible these include A Nested If constructs B If Then Elseif constructs These can be difficult to get right and are usually best avoided by using either a alist of If statements or b the Select Case construct However nested Ifs and If Then Elseif are included here for completeness but can be omitted if desired 6 15 1 Nested IF Statements optional If a condition has to be tested that depends on whe
173. nd Environments High Level Language Constructs 1 High Level Language Constructs 2 Procedures Functions and Standard Algorithms HERIOT WATT UNIVERSITY Topic 1 The Need for the Software Development Process Cont 1 1 1 2 Real life programs and classroom programming 1 3 Computing disasters e 22 4 0 4 6 wo ea a ak ee mt ed ws bi a ed 1 4 Well planned programs 19 SUMMALY 82 ae ariaa i a BI un ts tp skye bh al an eS Le 1 65 End of Topic Tests ta rn LUE ge ae a meet de Beh e ents IITFOGUIGUIO My xe sets Lee ve Pate chicks Act AN ami sha one By Bede AE Sc Bg aC A a 1 8 1 Examples of Computing Disasters 1 3 2 Information sources on computing disasters o o M DOO FW ND Prerequisite knowledge There are no prerequisites for this introductory topic Learning Objectives to understand what is meant by software development to recognise the professional issues that are involved in the development of a computer system to understand the need for software development to understand what is meant by well planned programs TOPIC 1 THE NEED FOR THE SOFTWARE DEVELOPMENT PROCESS 1 1 Introduction Computer systems are now an important aspect of everyday life It would be difficult to visualise a world without the day to day impact that computer
174. nd Sub Code 23 The program involves an If statement with an embedded for next statement If the capital sum entered does not meet the initial condition then control will be passed to the else statement If the condition is met then the program will continue and execute the for next statement and output results HERIOT WATT UNIVERSITY 156 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Note the output line which looks rather complex All it is doing is concatenating the output as a mixture of string and program variables Concatenation is not just reserved for strings Bank Interest Program Code and run the program You should end up with output as shown in Figure 7 5 for N 10 Nested loops aan 5 12 at1 10 24 at2 15 36 at 3 20 48 at 4 25 6 at 5 30 72 at 6 35 84 at 7 40 96 at 8 46 08 at 3 51 2 at 10 will will will will will will will will will will SEER ee ees Figure 7 5 HERIOT WATT UNIVERSITY 7 4 FIXED LOOP EXERCISES 7 4 Fixed Loop Exercises There are three exercises here e Mowing meadows Drawing right angled triangles and e the hardest Pythagoras Theorem Mowing meadows Use a nested loop to generate the following lines of a well Known verse 1 man went to mow a meadow 2 men 1 man went to mow a meadow 3 men 2 men 1 man went to mow a meadow N men N 1 men N 2 men 1 man went to mow a meadow Drawing right angled triangles
175. ndex or subscript Figure 7 13 Representation of the temperature array with temperature 2 18 0 and temperature 7 14 5 More generally an integer variable can be declared and used as the subscript e g temp temperature i which will take the value assigned in element number i of the array temperature and assign it to the variable temp This means that if you want to access the elements of an array sequentially you can do it using a for next loop where the variable for the subscript is automatically incremented each time you go round the loop Remember that the subscript variable can only be an integer A real is not allowed The examples within this topic will show you how you can access an array using a loop This is the most common way of marching through an array from beginning to end and as you will probably use this technique a lot in your programs HERIOT WATT UNIVERSITY 176 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 7 8 2 Declaring arrays Before you can use an array it must be declared at the beginning of the program with the other variable declarations The declaration provides the name of the array the number of elements and e the data type of the elements Like variables arrays can be declared using the Visual BASIC keywords Dim Public and Private that determines their scope If Dim is used then the array is private to the procedure in which it is declared Public makes the array visible from
176. ng departments one project will be similar to another Projects will have component parts which are similar for example many programs might require a sort routine to act on the contents of a database As time goes by a collection of modules is built up This collection is known as a module library Modules in the library can often be used over and over in new projects This saves time spent designing and coding If a module can be used without alteration there is the added advantage that it has been thoroughly tested and is reliable Use of unaltered modules reduces the time spent on the detection and correction of errors in the project as a whole Sometimes adjustments might be needed to a library module After the necessary work the module will require to undergo error and other testing Characteristics of module libraries On the Web is a interactivity You should now complete this task HERIOT WATT UNIVERSITY 2 6 TESTING 23 2 5 3 Review questions Q13 Which of the following is a quality of a good human computer interface It should be Windows based It can make a program execute faster It can make running a program a less irritable experience It should have lots of colour a b c d Q14 Which one of the following is not a high level language Visual Basic Pascal Assembler d C Q15 Which of these is not the result of compilation a Executable code b Object code c Machine code d So
177. ng is going to be long Your testing is likely to be fairly intensive and exhaustive It will be basic done by a separate team whose function is solely to test programs and find faults A program s lifetime may be The life of the program is short decades and it may undergo only long enough for you to pass changes called maintenance Similarly the documentation only The maintenance is probably going has to stand up to the examiner s to be done by someone who has scrutiny not written the original program and knows nothing about the original design decisions unless they have been documented Programs are written for use by The programs are not intended to other people who might have little be used understanding of computers HERIOT WATT UNIVERSITY 4 TOPIC 1 THE NEED FOR THE SOFTWARE DEVELOPMENT PROCESS Real life programs are written for use by clients who require the software systems to help them do their jobs They probably expect them to work like any complicated electrical appliance such as a TV You switch it on and it works Change channels and the channels change The brightness and other controls do what they are supposed to do without stopping the TV from working or having some unexpected side effects The programmers goal is to produce software as robust and easy to use as a TV In reality this is going to be impractical but when you design programs this should be something you need to bear in mind
178. nly understand machine code d all of the above Q2 Two translator programs are a compiler and an interpreter Which one of the following statements is true A compiler produces object code translating a program line by line A compiler produces object code for a whole program in one operation An interpreter produces object code for a whole program in one operation Acompiler translates and executes a program line by line a b c d Q3 Which one of the following error situations would be picked up by either a compiler or interpreter Run time error Logic error System error a b c d Syntax error 5 1 Introduction This topic will introduce you to the various types of programming languages that would be available at the implementation phase of the software development process As you will see the choices are numerous and expertise is required in matching the system specification with the most appropriate programming language available How programming languages translate source code into object code is further explained emphasising the advantages and disadvantages of the methods used 5 2 Programming Languages During the implementation phase of the software development process the program design will be coded using a suitable high level programming language High level languages help software developers to identify more with the problem rather than the hardware on which the final program will run i e they
179. notation a Structure charts b Stubs c Pseudocode d Stepwise refinement Q5 What statement refers to the term top down design a Itis a software testing approach b Itis breaking complex problems down into smaller units c Itis the detailed design of software logic d Itis the use of pseudocode Q6 Which of the following is a design methodology a Structure chart b Pseudocode c Stepwise refinement d Dry running Q7 For a designer an advantage of pseudocode is that he she can a Think more about the solution to the problem b Think more about the hardware c Think more about how the program will run d Think more about the speed of execution of the program Q8 One advantage of using stepwise refinement at the design stage is that it Reduces the chance of errors being introduced The designer does not have to bother with too much detail Makes the process more complex to novices The designer can concentrate on a small part of the problem at a time a0 0 9 HERIOT WATT UNIVERSITY 44 TOPIC 3 TOOLS AND TECHNIQUES 3 3 Test Data The purpose of test data is to determine that the system behaves as expected and is correct according to the program specification Preparing test data A program is to be written which will read a list of examination marks typed in at the keyboard and find the average examination mark The program should reject examination marks which are not within a specified
180. ntation documentation evaluation d Design documentation implementation evaluation Q2 Which one of the following is an essential item of documentation that should be produced during the software development process a Design notation b Test data c User interface d User and Technical Guides Q3 Which one of the following is NOT an aspect of the user interface of a program a Program listing b Help screens c Instruction screens d Screen layout 2 1 Introduction This topic considers the software development process From the initial client specification to the production of a working program can take considerable time and effort by the development team The process involves constant revision and evaluation at every phase which makes it an iterative process This ensures quality and efficiency in the final product Various models are introduced that aid the software development process but you will find that the perfect solution does not exist An individual may write a program for personal use If it does not work then it can be changed If more features or facilities are required then the individual can make amendments to their program This ad hoc method is not satisfactory in commercial environments where the goal is the creation of large scale software A more structured approach is necessary HERIOT WATT UNIVERSITY 12 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS The sole programmer Many unmanaged
181. number The error messages should be helpful and user friendly The program should deal correctly with numbers having four or more digits by giving the error message Value out of range Maximum of three digits numbers please Calculating Leap Years A leap year is a year which is exactly divisible by 4 unless it is exactly divisible by 100 in which case it is only a leap year if it is exactly divisible by 400 Write a program which prompts the user for a year and then displays if it is a leap year or not Note Use else if in your code You will also need to be careful that you do the tests for leap years and leap centuries in the correct order If you test for leap years first then 1900 is divisible by 4 but as it is not a leap century it will not be a leap year either HERIOT WATT UNIVERSITY 6 16 THE SELECT CASE STATEMENT 6 16 The Select Case Statement To implement multi way decisions the case statement provides a more concise and elegant representation than multiple else if andnested if statements which can get very difficult to follow The case statement is particularly useful when selection is based on a single variable or a simple expression This is called the case selector Note that the case selector must be an ordinal data type i e one whose values can be listed such as integer string or boolean The structure of the Case statement is Select case expression Case valuel Block of one or more statements Ca
182. ny changes made by the procedure to the value passed are local to the procedure and not passed back to the main program In other words the procedure can only modify a copy of the variable value and not the variable ActualValue itself You will see more of this later In a procedure call the word call may be omitted with only the procedure name and parameters required For example Call Square ActualValue becomes Square ActualValue This notation will be used from now on in all programs One of the disadvantages of call by value is that a copy of the actual parameter is always made in order to produce the formal parameter during the procedure call 8 2 1 5 Call by Reference Call by reference is used when information has to be passed out from a procedure to the main program Here the variables inside the procedure body are allowed to reference the memory location of the actual variable that passed it This means that as the actual parameters change as do the formal parameters A reference parameter does not pass a value of a variable but instead passes the address of the variable It is important that you understand the difference between value and reference parameters Consider the following procedures They are identical but one uses call by value and the other uses call by reference HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 207 Private Sub Add_10 ByVal Number As Integer Number Number 10 End Sub Private
183. o the program A change of computer system will require the program to be ported to the new system Perfective maintenance occurs in response to requests from the user to enhance the performance of the program This may be due to changes in the requirements or new legislation Such maintenance can involve revision of the entire system and can be expensive Matching definitions Maintenance On the Web is an interactivity You should now complete this task 2 10 Weaknesses of the software development process Problems are usually encountered when you use this model 1 Real projects rarely follow a linear sequential flow Apart from any software problems people change their minds and often there may be changes in legislation which mean that the program must be altered in order to comply with the new regulations No matter what the reason iteration always occurs and this creates problems because much of your work has to be re examined and revised 2 It is difficult for the customer to state all requirements explicitly at the start of developments The model depends on this and has difficulty incorporating customer uncertainty 3 Clients are frequently excluded from the development The working version of the program will not be available for the customer to see until late in the development cycle HERIOT WATT UNIVERSITY 2 11 SUMMARY 4 Developers work in isolation from the clients often for months only for the clients to
184. ocedure or function that represents a local variable Parameter passing The mechanism by which data is passed to and from procedures and the main program Perfective maintenance Takes place when a system has to be enhanced in some way e g program run faster Portable The ability of a program to run on different machine architectures with different operating systems Problem oriented The focus is on the problem and how it is to be solved rather than on the hardware on which the program will run Problem specification A document outline of what is to be solved in terms of programming a solution to a given problem Procedural language Also known as imperative languages because the programs follow a sequence of steps until they terminate The code is made up of procedures and functions Procedure A block of code that when called from within a program will perform a specific action Process An activity that is performed by a piece of software Programming team A section of the development team responsible for the coding testing implementation and maintenance of the software Project manager A member of the development team who is responsible for the supervision of the project The main tasks are to keep the project on schedule and within budget HERIOT WATT UNIVERSITY GLOSSARY 237 Pseudocode A notation combining natural language and code used to represent the detailed logic of a program i e algorithmic notation RAD
185. ogram will test the number to see if it is less than 10 and print the message that it is a single digit number If it 19 gt 9 at Will output double inceger number otherwise out of range Dim testNumber As Integer declare variable testNumer InputBox Please input amp number between 1 and 99 ask for number If testNunber gt O And testNumber lt 99 Then It testMumber lt 10 Then PicDisplay Print testNumber is a single digit number Else PicDisplay Print testNuxber is a double digit number display result of condition End If Else PicDisplay Print testNunber is out of range display result of condition End It End Sw end of program block Ejas 2l Figure 3 4 HERIOT WATT UNIVERSITY 46 TOPIC 3 TOOLS AND TECHNIQUES 3 5 Error Reporting Errors can occur at any of the stages in the development process This section will describe the following 3 categories of error e syntax errors e run time errors e logical errors Syntax Errors These are errors which result from incorrect use of the programming language structure They are detected during compilation and examples include e use of programming language keywords as variable identifiers e mis spelling of keywords e g PRNIT instead of PRINT e blocks that have a missing end marker e g FOR without NEXT e missing brackets semi colons These types of error can be very irritating as they prevent t
186. on This will be thoroughly checked against the design and against the original specification The high level code written at this stage is called source code which must be translated HERIOT WATT UNIVERSITY 78 TOPIC 5 LANGUAGES AND ENVIRONMENTS into machine code called object code that the computer understands There are two methods of translating source code into object code a compiler and an interpreter 5 9 1 Compilers and Interpreters A compiler which is a complex program in itself translates source code into object code that is then loaded into main memory and executed machine code program source program Compiler errors Another form of translation that converts source code into object code is an interpreter machine code program statement Interpreter errors Unlike a compiler an interpreter checks syntax and generates object code one source line at a time Think of this as very similar to a group of translators at a United Nations Conference who each have to convert sentences spoken by delegates into the native language of their representative When an error is encountered the interpreter immediately feeds back information on the type of error and stops interpreting the code This allows the programmer to see instantly the nature of the error and where it has occurred He or she can then make the necessary changes to the source code and have it re interpreted As
187. ons gt the constants used in the program variable definitions gt the variables used in the program main parts of the program INPUT PHASE read in data from keyboard file mouse etc CALCULATION process the data to give us the results we want OUTPUT send results to a window printer file disk etc HERIOT WATT UNIVERSITY 6 4 PROGRAM STRUCTURE End sub Sub procedures Procedure and function definitions End Sub Code 5 The program area contains the following A general area this area is public and variables declared here will be seen by all parts of the program Global variables should be avoided wherever possible More on this will be discussed later under the term scope A sub procedure cmd_click this contains the main program code that will be initiated in the event of a mouse click for example Within this code there are further declarations local to the sub procedure The declarations are Constants any fixed values which will stay constant throughout the program are declared here Variables variables other than global variables that are going to be used in the program are declared here Sub procedures any subprocedures required by the program are declared after the main sub procedure These are described more fully later on Functions any functions the program will use are also declared here These are described more fully later on The input may be from a variety of devices
188. oolyi And booly2 Then statements for false true Else statements for false false End If The following examples will show the If EndIf statement in use Example 1 Using an elseif statement to calculate the number of digits in a number Problem How can an else if statement be used to find out whether an integer number is within a certain range a positive number and how many digits it contains Solution A typical solution to this problem is shown here if number gt 1000 then n_digits 4 elseif number gt 100 then n_digits 3 elseif number gt 10 then n_digits 2 elseif number gt 0 then n_digits 1 else print Value out of range The above code shows an example of how this could be achieved e You start testing if the variable number is greater than or equal to 1000 in which case there are 4 digits you must be assuming that the variable number is not HERIOT WATT UNIVERSITY 134 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 greater than 999 and the variable n_digits is set to 4 If it is not greater than or equal to 1000 then you move onto the next branch of the if statement The next condition tests the variable number to see if it is greater than or equal to 100 If this is true then you know the variable number has a value between 100 and 999 and so it must have 3 digits and the variable n_digits is set to 3 Again if this condition is not fulfilled then you move onto the next branch of
189. ors HERIOT WATT UNIVERSITY 3 4 STRUCTURED LISTING 45 Q13 The last remaining errors in a program are not easy to remove because a b c d They could remain hidden until the program is run under all conditions The compiler is not very efficient De bugging procedures are not effective enough They will not affect the running of the program since most errors have been found 3 4 Structured Listing A structured listing is a hard copy of the program source code It is important that the source code is laid out in accordance with the conventions of the implementation language The code should be properly indented this helps people follow the structure of the code e Meaningful names should be used for modules constants and variables The use of internal commentary will help to explain the logic of the code to others and also serve as a documentation aid for the programmer A structured listing can be produced at any time during implementation It can serve as a tool for checking program logic and also form part of the final software documentation Figure 3 4 shows a structured listing of a program coded in the language Visual Basic m Project Form Code Option Explicit Private Sub Command Click start of program block progres nested_IF 15th February 2004 Program by Fred Fink This program vill prompt the user to enter a number between 1 and 99 The pr
190. ot equal so pointer moves on 3 34 is compared to key Not equal so pointer moves on 4 76 compared with key Success Key found at position 4 in the list cn manne 8 5 2 Linear Search Examples There are at least two variants of the linear search algorithm The simplest searches the entire list from beginning to end Linear search 1 searching the entire list prompt the user for the search key start at the first element in the list do while not end of list if the current element lt gt search key then move onto the next element in the list else output search key and position end if loop oo N OO O1 amp NN PB This is not a very efficient way of doing things Why bother to search the remainder of a list when the item has been found There are instances when you will want to search HERIOT WATT UNIVERSITY 218 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS the entire list e g if you wish to replace all words in a list that begin with L to words that begin with P then the search would stop when you reach the end of the list The alternative algorithm makes use of a complex condition and a boolean variable Linear search 2 stopping when the search key is found set found to false prompt the user for the search key start at the first element in the list do while not end of list and found is false if the current element search key then set found to true display message else move onto
191. other The program responds by printing the bigger of the two Use the code fragments in the examples above to help you and make sure that the program has user friendly prompts for the input and output Even or odd Write a program to test if a user entered number is even or odd In this program you will have to use the modulus operator mod to calculate the remainder when the value stored in the variable number is divided by 2 An even number has no remainder if divided by 2 Calculating wages Write a program to calculate the commission based wages of a computer salesman His basic wage is 50 per week and he is expected to sell at least 10 computers If he sells more than 10 computers he receives an extra 5 50 per computer he sells after the 10th computer The basic algorithm could be drawn as shown in Figure 6 12 input computers sold calc commission output pay Figure 6 12 HERIOT WATT UNIVERSITY 6 14 COMPARISON OPERATORS 6 14 Comparison Operators There are two kinds of comparison operators that allow comparison within Visual BASIC 1 Relational 2 Logical These are very useful when implementing selection constructs 6 14 1 Relational operators Relational operators are used for testing of conditions They are used to construct the expression which is used in the if statement The relational operators check whether two quantities are the same or whether there is a difference betw
192. ow set array 1 12 What are the array contents now a array 8 23 5 19 8 0 7 52 b array 12 23 5 19 3 0 7 52 c array 8 12 5 19 3 0 7 52 d array 8 23 12 19 3 0 7 52 e array 8 23 5 12 3 0 7 52 f array 8 23 5 19 12 0 7 52 g array 8 23 5 19 3 12 7 52 h array 8 23 5 19 3 0 12 52 HERIOT WATT UNIVERSITY 180 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 i array 8 23 5 19 3 0 7 12 j none of the above Q22 Again starting with an 8 element array with a subscript range of 0 7 e g array 8 23 5 19 3 0 7 52 Set array 3 9 element with index 6 11 and array 6 4 What are the array contents now array 8 23 5 9 3 0 4 52 array 8 23 5 19 9 4 7 52 array 8 23 5 9 3 4 7 52 a0 0 9 array 8 23 5 19 9 4 4 52 e none of the above Q23 Set up an array that can hold 4 values with a subscript range of 0 3 Initialise the array to hold all 0 values Now set the following values e array 1 9 e array 2 3 What are the contents of the array now express in format of array 3 2 5 O Q24 Set up an array that can hold 10 values with a subscript range of 0 9 Initialise the array to hold all 0 values Now set the following values e array 4 6 array 8 2 e array 1 7 e array 7 3 What are the contents of the array now express in format of arr
193. own below Option Explicit Private Sub Commandi_Click program CalculateAverageTemp program to calculate average temperature 20th February 2004 Program by Fred Fink Dim Store 13 As Single Dim total As Single average As Single Dim day As Integer total 0 0 initialise total HERIOT WATT UNIVERSITY 7 8 ARRAYS 183 For day 0 To 13 Store day InputBox Enter temperature for the day PicValues Print day total total Store day PicArray Print Store day Next day average total 14 PicResult Print Format average standard End Sub This file Average Temp2 txt can be downloaded from the course web site Code 30 As the temperature values are entered they are stored in the array Store When the loop terminates the value of average is displayed The program output is shown in Figure 7 15 Average temperature 0 l 2 3 4 5 6 5 8 9 Figure 7 15 HERIOT WATT UNIVERSITY 184 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Version 2 Adapt version 1 as above Test the new version 7 8 6 Random Events Using arrays makes it easy to simulate many numerical activities that otherwise would be fairly tedious to do manually For example analysing the results of tossing a coin 1000 times throwing die or spinning a roulette wheel can all be dealt with in one dimensional arrays Such simulations make use of random numbers that can be generated between upper and lower limits for examp
194. ox Please enter a name The user then complies with the request to enter a name Should a numerical value be required by the program then the input format is identical but a numeric variable is used Numberi InputBox Please enter a value Number program 50 50 Number program Please enter a value In this case the value 12345 is input to the program a caption appears in the title bar and the InputBox appears at coordinates 50 50 In most cases only the prompt is used 6 3 4 2 Use of the Text Box for Input A text box can be used instead of an input box The main advantage of a text box is that a user can type in much more information during the execution of a program Since text boxes can hold large amounts of text it is best that they are created using a vertical scroll bar HERIOT WATT UNIVERSITY 90 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Text Box THIS IS AN EXAMPLE OF ENTERING A LARGE AMOUNT OF TEXT INTO A TEXT BOX NOTICE THAT VERTICAL SCROLL BAR IS PRESENT TO ENSURE ALL THE TEXT IS READABLE SHOULD IT OVERFILL THE TEXT AREA A TEXT BOX CAN LSO BE USED TO INPUT NUMERICAL VALUES INTO A PROGRAM AS LONG AS THE TEXT vi In the properties window the options Vertical scroll bar and Multiline True are set 6 3 4 3 Exercises on Input Methods Exercise 1 Open a new Visual BASIC project and experiment with adding buttons and text boxes to the form from the toolbox window Use the properties windo
195. oximation For accuracy you need to use integers 2 The data type variant is the default mode in Visual BASIC and will be discussed later in the topic It should not normally be used Identifying data types On the Web is an interactivity You should now complete this task 6 6 Naming variables An important aspect of any language is the rules for naming the objects such as constants variables subprocedures and functions There are five rules in Visual BASIC which prescribe valid variable names All Visual BASIC variable names 1 must begin with a letter 2 must contain no spaces 3 must only consist of letters or digits with no punctuation marks except the underscore character 4 can be no longer than 255 characters 5 cannot use Visual BASIC reserved words Some of these keywords are listed in Table 6 3 and must not be used as variable names Table 6 3 if ease public repeat progran ana sf string ao print fx A more complete list of keywords can be found in any good Visual BASIC manual The variable names shown in the table are valid pay period ma imoya HERIOT WATT UNIVERSITY 6 6 NAMING VARIABLES The variable names shown in the table are not valid Why FO birthday const badvaribe Online there is an interactivity Naming variables You should attempt this now Sentence completion variables On the Web is an interactivity You should now complete this task 6 6 1 Rev
196. positive value of the variable index that will cause the following code to fail Dim array_1 19 As integer Dim X As integer index As integer array_1 index array_1 index index a0 0 gw x e n lt O N 7 8 5 Calculating the average of the values stored in an array Problem Write a program to access each of the temperatures of a room over 14 days Calculate the average temperature during the period Solution First try A typical solution to this problem which doesn t use an array is shown in Code 29 HERIOT WATT UNIVERSITY 182 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Option Explicit Private Sub Commandi_Click program CalculateAverageTemp program to calculate average temperature 20th February 2004 Program by Fred Fink Dim total As Single average As Single Temp As Single Dim day As Integer total 0 0 initialise total For day 0 To 13 Temp InputBox Enter temperature of day PicValues Print day total total Temp PicArray Print Temp Next day average total 14 PicResult Print Format average standard End Sub This file Average Temp txt can be downloaded from the course web site Code 29 Refinement using an array The program in code 7 10 gives correct output and result but does not allow the programmer to re use the data which has been entered To do this we need to use an array An improved version using a 1 D array to store the data is sh
197. ption Explicit Dim SearchKey As Integer Pointer As Integer Fill As Integer Dim Occurrence As Integer Dim List 15 As Variant Private Sub Command1_Click Program Counting Occurrences 229th February 2004 gt Program by Fred Fink HERIOT WATT UNIVERSITY gt This program will perform a search on TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS an array holding 16 random integers and output occurrences of an input value Setup Populate_List List Enter_search_item SearchKey Call procedures Search_for_item Pointer SearchKey Occurrence List End Sub Private Sub Setup Randomize PicList Cls PicResult Cls PicList Print Pointer 0 Occurrence End Sub 0 Private Sub Populate_List ByRef List Dim Fill As Integer For Fill 0 To 15 List Fill Int 49 Rnd 1 PicList Print List Fill Next Fill End Sub Initialise variables gt and clear output boxes Fill array with 216 random numbers Private Sub Enter_search_item ByRef SearchKey User input search item SearchKey InputBox Input search item to count End Sub Private Sub Search_for_item ByVal Pointer ByVal SearchKey ByVal Occurrence ByRef List Do If List Pointer SearchKey Then Occurrence Occurrence 1 End If Pointer Pointer 1 Loop Until Pointer gt 15 PicResult Print Search item SearchKey found Occurrence times in the list End Sub Private Sub Command2_Click End End
198. r Sunny Then HERIOT WATT UNIVERSITY 128 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 PicDisplay Print iTemp deg and weather Wash the car Else PicDisplay Print iTemp deg and weather No way End If End Sub Private Sub cmd_Exit_Click End End Sub This file WashCar txt can be downloaded from the course web site Code 14 The program output is shown in Figure 6 15 Formi MALE 18 deg and Sunny Wash the car 14 deg and Sunny Wash the car 22 deg and Rainy Wash the car 14 deg and Rainy No way End Program Figure 6 14 6 14 5 Logical NOT Use of the logical NOT operator is shown below if Vone 6 and not Vtwo 6 then statement 1 end if In this example if Vone is equal to 6 and Vtwo is not equal to 6 then statement 1 is executed The not operator inverts true false values e g if the value is true then not true false HERIOT WATT UNIVERSITY 6 14 COMPARISON OPERATORS 129 Example The Word and Word program could easily be modified to include the NOT operator Rewrite the code and run the program 6 14 6 Review Questions Q17 Operators are used within expressions to assign values to variables and perform calculations Which one of the following operators has the highest precedence in Visual BASIC d Q18 What would be the result of evaluating the following expression 3 4 6 4 Q19 Which one of the following describes seque
199. r in an if statement Problem Construct an if statement that will display a message to the screen if two variables Vali and Val2 are equal Solution A typical solution is shown here Dim Vali As Integer Val2 As integer if Vali Val2 then Print Vali and Val2 are equal end if Sentence completion relational operators On the Web is an interactivity You should now complete this task 6 14 2 Logical Operators Logical operators test conditions as either being true or false In computer programming they are referred to as Boolean operators named after George Boole a mathematician and logician 6 14 3 Logical AND Logical AND means that an expression is true only if both the part before the AND and the part after the AND are true Both must evaluate to true So if number lt 0 and number gt 10 then the expression will always evaluate to false Why Because a number cannot be less than zero and greater than 10 at the same time and both must be true for the AND statement to produce a true result Use of the logical AND operator can be seen in the expression below if Vone 6 and Vtwo 6 then statement 1 else statement 2 End if This code means that when both Vone and Vtwo are equal to 6 then statement 1 is executed If either or both of the conditions is false then statement 1 is ignored and execution passes onto statement 2 Online there is an interactivity which you should a
200. ractivity which you should attempt 3 6 Summary The following summary points are related to the learning objectives in the topic introduction much has to be done in terms of design and testing of software before the coding and implementation stages various graphical design constructs are available including structure charts and diagrams top down design with stepwise refinement is a well established technique testing is an extremely time consuming process and should find and resolve all syntax errors run time errors and logical errors the main aim is to produce software that is reliable robust portable efficient and maintainable 3 7 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY 48 TOPIC 3 TOOLS AND TECHNIQUES HERIOT WATT UNIVERSITY Topic 4 Personnel Contents Arde Hntrodu tion Sefa k 202 Bape eran eee eee eed ed a BALE RSS A 4 2 ME GHENT A Re ee Gi Sacks cine ete ese ea m Gy ese 43 The Project Manager 4 4 The Systems Analyst 4 4 1 Collection of Information 4 4 2 Production of the problem specification 4 4 3 Review Questions 4 5 The Programming Team 4 6 Independent Test Group 4 6 1 Roles in classroom programming
201. ram is a valuable aid to the programming team This is because They are easy to use and can be understood by the user They allow for faster program execution They are required during evaluation They represent the design in a visual way a b c d Q3 Pseudocode can be considered to be an intermediate stage between High level language code and machine code English and high level language code English and machine code a b c d Source code and object code 3 1 Introduction In this topic you will learn about the various methods that are used to aid the system developers and programming team to implement solutions according to program specifications The first important issue you will come across is that program coding is only attempted after extensive and rigorous series of analysis and design stages are completed Efforts at these initial stages pay dividends at the coding stage reducing testing debugging and maintenance of the programs The main tools and techniques include Design methodologies e Test data e Structured program listing e Comprehensive error reporting e Module libraries HERIOT WATT UNIVERSITY 38 TOPIC 3 TOOLS AND TECHNIQUES 3 2 Design methodologies and notations The design of software is something of an art and normally follows a clear design methodology A methodology is an agreed technique used to design software It includes both approaches to designing software and the
202. range and provide a suitable error message to the user Q9 1 Write down what you think an acceptable range for an examination mark would be 2 Write down an algorithm in pseudocode notation to represent the data input part of a solution to this problem 3 Copy the headings in the table below and construct at least 8 test data entries to demonstrate how you would verify the correctness of the program Expected Result Actual Resul Sentence completion test data On the Web is an interactivity You should now complete this task 3 3 1 Review questions Q10 Which one of the following options states the main purpose of test data To determine that the system meets the specification To prove the absence of errors To show that the programmers have been careless To minimise the number of errors in the program a b c d Q11 Error detection can be time consuming Which one of the following could be added to a program to help detect errors a Suitable commentary throughout the program b Output statements at key points in the code c Specific error detecting code d Nothing can be added Q12 One example of a fault avoidance technique in developing software is Take more time to design better software Hire more programmers so that errors will be easier to detect Design input routines that will not crash when presented with unexpected data a b c d Make sure that that the code is specifically written to avoid err
203. re readable When defining a list of variables with the same type specifier the variables can all be defined on the same line as the type specifier or separate type specifiers can be used for each variable For example Dim numberi As integer number2 As integer sum As integer is equivalent to HERIOT WATT UNIVERSITY 6 8 DECLARING CONSTANTS 107 Dim numberi As integer Dim number2 As integer Dim sum As integer However the statement Dim numberi number2 sum As integer will assign sum as integer with number and number2 being assigned variant 6 8 3 String variables and functions A string is simply a collection of characters that are defined within quotes The following are examples of string values coffee This program is not working XYZ February 16 2004 Visual BASIC 6 Shrove Tuesday is pancake day 54 The quotation marks are very important since they tell Visual BASIC that the enclosed characters are a string Characters not enclosed in quotation marks are considered to be a numeric variable or some other part of the Visual BASIC language Note The string value 51 does not equal the value 51 You might think that it s a value for an integer but it s not However there is a Visual BASIC function VAL that will convert string variables to values The following statement NumericalValue VAL 51 will allow the variable NumericalValue to be assigned the integer value 51 Of course the
204. reverse is also true Given a value it can be converted into a string using the Visual BASIC STR function The following statement StringValue STR 51 will allow the variable StringValue to be assigned the string 51 Two other useful functions are CHR and ASC The following examples show how they are used LetterValue ASC A will assign the value 65 to LetterValue This is the ASCII code for the letter A Letter CHR 66 will assign the string B to Letter since the ASCII code for B is 66 Table 6 4 summarises the string functions HERIOT WATT UNIVERSITY 108 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Table 6 4 VAL Converts string to value the integer 66 Converts value to string the string 77 ASC Converts string to ASCII ASC D the ASCII value 68 value ASCII val CHR te Sel vane te CHR 68 the character D String Functions Online there is an interactivity which you should complete now 6 8 4 Concatenation Concatenation is simply joining string variables together to make longer strings The operator is the ampersand symbol amp When two or more strings are combined the second strings are added directly to the end of the preceding string The result is a longer string containing the full contents of both source strings The following example shows concatenation structure NewString StringOne amp StringTwo amp StringThree Here NewString represents the variable that contain
205. rms within the guide HERIOT WATT UNIVERSITY 27 28 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS 2 7 2 Technical guide The technical guide will contain information about the hardware and software requirements of the program The hardware specification will include details of the processor type and speed RAM required RAM desired monitor resolution graphics and sound card specifications etc It will also contain instructions about configuring the program DOCUMENTATION Software designed to operate or run on networks can be very complicated and require a good deal of expertise Technical guides can be very large and cumbersome and difficult to navigate Sentence completion Documentation On the Web is an interactivity You should now complete this task HERIOT WATT UNIVERSITY 2 8 EVALUATION 29 2 8 Evaluation Evaluation is the formal monitoring of a system to ensure that it is performing its purpose accurately efficiently cost effectively and in a timely manner The performance of the system must be matched against a given set of criteria such as the initial project specification Evaluations of various kinds are an important aspect of the software development industry Evaluations are used to determine if systems are usable cost effective conforming to performance criteria etc Evaluation is based on observation interviews and questionnaires Additionally techniques such as automatic data logging
206. rogram does what it is supposed to do In the full software development process test data should be prepared before implementation That is before you have invested time and effort in writing the code All too often there is a temptation especially at classroom level to start coding a program as soon as possible without having produced adequate test data But experience shows that this is a mistake Once you have written the code you will tend to go easy on it and let the program s behaviour shape what you expect of it You are going to be too kind to it MURPHY s LAW 1 MURPHY s LAW 2 The quicker program coding is started the Murphy s Law 1 is correct longer the project will take Testing follows a test plan or strategy Testing should be systematic That means testing is planned e everything is tested in a logical order e the results of testing are recorded With most software projects the usual strategy is to test the software twice The methods are called alpha testing where the software is tested within the organisation beta testing where the software is tested by personnel outside the organisation or by certain members of the public This is sometimes called acceptance testing HERIOT WATT UNIVERSITY 2 6 TESTING 2 6 2 Alpha testing Test data is based on the specification Data will be designed to test three aspects of the program normal operation data that the program has essentially b
207. rogramming COMAL COMmon Algorithmic Language BASIC Beginners All Symbolic Instruction Code Artificial Intelligence in LOGic One of the first interpreted languages designed for beginners to programming in the 1960s The language promoted the use of structured code as opposed to the spaghetti code from using BASIC PROLOG PROgramming Used in the construction of Al applications expert systems and in the teaching of Al Derived from UNIX as the C shell it now has many uses in programming being very close to assembly language Alternatively high level languages can be classified according to their structure and purpose Although quite an extensive list for the purposes of this topic the following categories are of importance 1 Imperative procedural Declarative logical Event driven WwW ND Scripting Two other types which you do not need to know about for this course are O1 Object oriented 6 Functional 65 HERIOT WATT UNIVERSITY 66 TOPIC 5 LANGUAGES AND ENVIRONMENTS A table based on this language classification is shown Table 5 2 Table 5 2 Classification based on structure Programming Purpose Language Pascal procedural general purpose language widely used Visual BASIC event driven windows interface applications multimedia PROLOG declarative artificial intelligence artificial intelligence Visual Poe event omahe _ used as fron
208. rograms do not terminate by default By adding an extra button on the form and programming this with End between the lines of code this will terminate the program This will be used on all subsequent programs Sample output is shown in Figure 6 11 Form 8 is a single digit number 0 is a single digit number 86 Is this double digit number 99 Is this double digit number End Program Figure 6 11 Further examples Example 1 Problem What is the output of the following code Dim Numberi As Integer Number2 As Integer Numberi 10 Number2 5 if Numberi gt Number2 then Print Numberi is bigger else Print Number2 is bigger End if Solution This piece of code first declares two integer variables Number1 and Number2 Number1 is assigned a value of 10 and Number2 is assigned a value of 5 The condition for the if statement is is Number1 greater than Number2 If this is true then the statement Number is bigger is displayed If the condition is false then the statement Number2 is bigger is displayed on the screen HERIOT WATT UNIVERSITY 122 30 min 20 min TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 In this case the condition is true since Number1 has a value of 10 which is greater than the value of 5 that has been assigned to Number2 and so the output from this code is Number1 is bigger Which is bigger Write a program which prompts a user to type in two numbers first one then the
209. rs and students who contributed to the SCHOLAR programme and who evaluated these materials Grateful acknowledgement is made for permission to use the following material in the SCHOLAR programme The Scottish Qualifications Authority for permission to use Past Papers assessments The Scottish Government for financial support All brand names product names logos and related devices are used for identification purposes only and are trademarks registered trademarks or service marks of their respective holders Contents 1 1 1 2 1 3 1 4 1 5 1 6 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 1 3 2 3 3 3 4 3 5 3 6 3 7 4 1 4 2 4 3 4 4 4 5 4 6 4 7 The Need for the Software Development Process Introd ction 4 24 aa a a i aa AEE E goth t en dans Real life programs and classroom programming Computing disasters Ma o oo o e acted del se ee a a Well planned programs Summary End f TOPIC TeSt i 2 20e G4 ni a ok a panda a an ee ag as we Features of Software Development Process Introd ction as or ai na Bo aa Bae O ee ok Ble ee A The need for iteration The Analysis Stage naoa RAA ee SET ER eG The Design Stage be oe antes alee a A Fer Se ahd The Implementation Stage Testing The Documentation Stage Evaluation Maintenance 45 2 LR RE SR he he ithe cay Seed
210. s 1 linear search 2 count occurrences 3 find maximum 4 find minimum 8 8 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY 228 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS HERIOT WATT UNIVERSITY Topic 9 End of Unit Test Contents 229 230 TOPIC 9 END OF UNIT TEST An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY GLOSSARY 231 Glossary Acceptance testing Testing of software outside the development organisation and usually at the client site Adaptive maintenance Takes place when a program s environment changes for example a different operating system Algorithm A detailed sequence of steps which when followed will accomplish a task Alpha testing Testing of software within the development organisation Beta testing Testing of software outside the development organisation using clients or selected members of the public Bottom up design A method of program refinement that starts with individual modules and builds them up into a complete program Boundary testing Running a program with test data that represents the extreme upper and lower values Within this range the program should operate normally Bugs A bug is a program error Bytecode This is produced by JavaScript and is a form of machine code that runs under the Java virtual environment The latter is freeware and enab
211. s 2 aaa a 7 8 3 Simple 1 D array manipulation 7 8 4 Review Questions 7 8 5 Calculating the average of the values stored in an array 7 8 6 Random Events 7 8 7 Simulation Of TOSSING A COIN 428 eee eae eae ee dd dd cn wad 7 8 8 Testing for Palindromes using an array 7 9 Summary 7 10 End of topic test 147 147 148 149 151 153 155 157 157 159 159 160 162 163 165 165 167 168 171 172 173 174 176 177 180 181 184 184 186 190 190 145 146 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Prerequisite knowledge Before studying this topic you should be able to describe and use the following constructs in pseudocode and a suitable high level language fixed loops conditional loops using simple and complex conditions e nested loops e 1 D arrays Learning Objectives After completing this topic you should be able to e declare a 1 dimensional array e access array elements e manipulate data within arrays using iterative structures e format output HERIOT WATT UNIVERSITY 7 1 INTRODUCTION Revision Q1 An array is described as a structured data type This means that a Data items are all in order b Data items will take up a lot of computer memory c Dataitems of the same type are grouped together d None of the above Q2 A 1 D string array called Days 0
212. s Print Message 2 End Sub Private Sub BlankLines Print Print Print End Sub As it stands BlankLines isn t very well structured As programmers we should always be a little wary when we find ourselves repeating code It might be better to put the Print statements within a loop structure The following refinement should produce a more acceptable program Private Sub BlankLines for n 1 to 3 Print Next n End Sub The program is still not very flexible We should be able to tell the procedure how many blank lines to output This is achieved using parameters and we will come back to this section of code later Program with parameters A user is asked to input numerical values between 1 and 30 Write a section of code as a procedure to validate user input between these two values Show how it would be called from the main program 8 2 1 2 Parameter passing How are parameters used to pass information between sub programs To see how this works consider the following program Specification The program must ask a user to enter their name and date of birth It should then convert HERIOT WATT UNIVERSITY 198 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS the date of birth into standard format ddmmyyyy and calculate the person s age The name standard format d o b and age should then be displayed on the screen Design There are 3 clear stages In pseudocode these could be written as 1 g
213. s have on our lives cash machines supermarket tills petrol pumps travel tickets payslips and bills the Internet and e commerce and so on The first few topics of this unit describe the development of software The development of software follows a definite process known as the software development process SDP As you should already know this process can be split into 7 stages analysis implementation documentation By following these 7 stages it should be possible to design and build software systems that are e of high quality e cost effective produced to specification e delivered on time The idea is to bring together a variety of tools techniques and methods which will help create reliable software Programs can be designed to be maintainable that is they are presented and documented so clearly that they can be updated by another programmer at some future time There are many reasons why the software development process is so important These include 1 increased complexity and sophistication of computing systems 2 escalating costs of software systems 3 unreliable software systems 4 the cost of maintaining software HERIOT WATT UNIVERSITY 1 2 REAL LIFE PROGRAMS AND CLASSROOM PROGRAMMING Following the software development process is especially important in the development of real life programs If you understand the problems of large scale programming the need for the soft
214. s of 1s and 2s that represent heads and tails The following code segment should accomplish this For toss 0 to 999 If HeadsTails toss 1 then heads heads 1 else tails tails 1 end if next toss Finally add the code to output the number of heads and tails A typical output is shown in Figure 7 16 ormi Number of heads Number of tals Number of tosses pe Figure 7 16 Heads and Tails Program Code the program and run it a few times to see if you get the expected result i e 500 heads and 500 tails Dice Program The program can easily be modified to simulate throwing a die Exercise HERIOT WATT UNIVERSITY 186 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 Amend Code 38 to output the results of throwing a die about 50 times 7 8 8 Testing for Palindromes using an array Problem Write a program which will read in a sequence of words The characters will be read into an array and the program should then determine if the sequence is a palindrome Note A palindrome is a sequence of number characters words etc which is the same when read from either direction The following examples are palindromes if we ignore spaces the sequence being the same when read from left to right or from right to left 2345432 madam im adam was it a car or a cat I saw live not on evil eve This program may seem more complicated than it really is If you follow the explanation you will see that
215. s the result of the concatenation operation StringOne StringTwo and StringThree all represent string variables Note that the ampersand must be preceded and followed by a space Example of concatenation Example 1 The statement Print Man amp chester would produce the string Manchester Example 2 Stringi This is String2 con String3 cat String4 en String5 ation Print String amp String2 amp Strings amp String4 amp Strings will produce as output This is concatenation HERIOT WATT UNIVERSITY 6 9 VARIABLES AND SCOPE 109 6 9 Variables and scope Variables have another important characteristic called scope This determines which parts of a program are able to see the variable and change its value The scope of a variable is determined not only by the type of declaration but also the declaration s location For instance the Dim keyword assumes different meanings in different parts of a form s code In Visual BASIC variables can be declared as shown in Figure 6 8 Declarations section P TT Fonsi Code mmand1 Option Explicit Public variableGLOBALL Public variable visible throughout program Private varisbleLOCAL1 Global variable visible to entire form Dim variableGLOBAL1 Global variable visible throughout program Private Sub Commandi Click Dir variableLOCAL Local variable only visible vithin aub procedure End Sub Private sub procedure
216. say a command button is pressed These procedures are named by Visual BASIC by concatenating the name of the object code and the name of the event according to the syntax Sub Command_Click End End Sub You will recognise this code which ends a Visual BASIC program 8 2 1 1 General Procedures The basic structure for a general procedure is Sub ProcedureName formal parameters Declarations Statements End sub Notes 1 The name ProcedureName or identifier is what is used when the procedure is called and the name conforms to the same rules of naming variables 2 Data is passed to and from the main program using the procedure parameters Or arguments enclosed in parentheses Not all procedures however need to have parameters 3 The declarations and statements follow an identical pattern to normal programming constructs 4 Procedures are normally declared private and their scope is limited to other procedures and variables within the current form Here to get us started is a simple little procedure that prints blank lines on a form This might be useful for putting spaces into program output Private Sub BlankLines Print Print Print End Sub HERIOT WATT UNIVERSITY 8 2 PROCEDURES AND FUNCTIONS 197 This could be called in the action part of the main block as Call BlankLines Its use in a program could look like this Private Sub commandi_Click program lines Print Message 1 Call BlankLine
217. se value2 Block of one or more statements Case value3 Block of one or more statements Case Else Final block of one or more statements End Select The expression is compared with each of the case values in turn If there is a match the relevant statements are executed If there is no match the Else statements are executed Several worked solutions to problems are given here make sure you understand what is going on in these examples Run these programs for yourself and experiment with making changes to the code to ensure you understand what is happening 6 16 1 Select Case Example 1 Example 1 Write a program to input an integer between 1 and 7 and the day of the week will be output Solution Use the following algorithm 1 ask user to input number between 1 and 7 inclusive 2 select case number 3 case is 1 output Sunday 4 case is 2 output Monday 5 case is 3 output Tuesday 6 case is 4 output Wednesday 7 case is 5 output Thursday 8 case is 6 output Friday 9 case else output Saturday HERIOT WATT UNIVERSITY 137 138 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 10 end select Note the use of keyword is Whenever a condition is expressed within a statement the keyword is is used to impose the condition The full Visual BASIC program is shown in Code 17 Option Explicit Private Sub Commandi_Click Use of the Case Select statement 1 15th February 2004 gt Program by Fred Fink
218. sed to run the software the nature of the problem to be solved a b c d an outline of the problem solution 2 4 2 Designing the human computer interface The human computer interface is all that a user sees of a program A program s viability often relies on the quality of the HCI A good interface makes things easier for the user A bad interface can introduce mistakes and cause irritation Modern HCls are often designed as Graphical User Interfaces GUIs which provide a WIMP environment WIMP stands for Windows Icons Menus Pointers although some HERIOT WATT UNIVERSITY 18 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS textbooks refer to Windows Icons Mouse Pulldown menus A GUI provides a set of Windows which contain Icons and Menus The user controls the program by means of a Pointer which reflects movement of a mouse trackerball or other input device The WIMP environment My computer X EMEsit View Help Open Browse with Pro 5 Paint Explore 4 Find d Scan for Viruses Add to Zip Menu Create Shortcut ins Delete Ravens briefcase Properties Ico n A Window Close Pointer The HCI must allow easy navigation Users should be able to move from one screen to another in a straightforward manner and to leave screens when they wish Some sites on the Internet for example include a site map to show the user how
219. sual BASIC Q8 d They are low level languages Answers from page 77 Q9 a Q10 d Q11 c Q12 d Programs have no pre defined pathway They describe a problem rather than how to solve it Macros automate repetitive tasks Changing audio CDs Answers from page 80 Q13 c A compiler creates an independent machine code program Q14 a Looping structures have to be interpreted each time they are entered Q15 a Computers can only understand machine code HERIOT WATT UNIVERSITY 248 ANSWERS TOPIC 6 6 High Level Language Constructs 1 Revision page 83 Q1 d Answer 5 8 3 2 Q2 c 6 Q3 d All of the above Answers from page 99 Q4 c 17 5 Vat Q5 a It makes it easier for programmers to locate and fix errors Q6 d Integer Q7 c Integer long Answers from page 103 Q8 The variable number2 has not been declared There will be no output since the variable sum has no value and has not been declared Also the Print statement is wrong Answers from page 111 Q9 c Global Q10 d All three statements above Q11 b They are hidden from other procedures and functions Q12 c The extent to which the variable can be seen by the rest of the program Q13 d It can have only the values true or false Answers from page 113 Q14 c 1 Q15 a 3 5 Q16 b 3 Using the logical AND operator in an if statement page 126 If number1 gt 10 AND number2 gt 10 Then Print HERIO
220. t 100 then grade A 7 else number out of range 8 end if 9 If mark gt 0 and lt 100 10 display grade 11 end if HERIOT WATT UNIVERSITY 6 15 OTHER FORMS OF IF STATEMENT 135 The full Visual BASIC program is shown in Code 16 Option Explicit Private Sub Commandi_Click Marks and grades program 15th February 2004 Program by Fred Fink This program will prompt the user to enter a mark and a grade will be output Dim iMark As Integer Dim sGrade As String iMark InputBox Please input a test mark If iMark gt 0 And iMark lt 30 Then sGrade E ElseIf iMark gt 30 And iMark lt 50 Then sGrade D ElseIf iMark gt 50 And iMark lt 65 Then sGrade C ElseIf iMark gt 65 And iMark lt 85 Then sGrade B ElseIf iMark gt 85 And iMark lt 100 Then sGrade A Else PicDisplay Print iMark is out of range Try again End If If iMark gt 0 And iMark lt 100 Then PicDisplay Print iMark grade sGrade End If End Sub Private Sub Command2_Click End End Sub This file Grades txt can be downloaded from the course web site Code 16 HERIOT WATT UNIVERSITY 136 20 min TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Figure 6 16 shows the program output Form 105 is out of range Try again Figure 6 16 Calculating the number of digits in a number Write a program which will calculate the number of digits in a
221. t end to develop user ne nace Java object oriented platform independent an object oriented language VBscript creating creating andeditingmacros creating andeditingmacros macros FORTRAN 9 90 FORTRAN 90 object oriented scientific and software engineering Lisp functional artificial intelligence uses many other languages are derived from it JavaScript writing and enhancing web pages BASIC procedural easy to learn originally developed to teach non specialists the art of programming FORTRAN scientific programming language The above list is not in any way rigorous There are many instances of particular languages fitting into more than one category For example although Visual BASIC is listed as an imperative language it can be used to create event driven programs and has many features in common with object oriented languages 5 4 Procedural Imperative languages A procedural imperative programming language tells the computer how to do something written as an ordered sequence of steps that describe exactly what it must do at each step These instructions which form the basis of an algorithm are followed in written order by the computer Three basic constructs are used to define the order of the steps 1 sequence the logical ordering of steps 2 selection a step or sequence of steps are performed if a condition or set of conditions is true 3 iteration a step or sequence of steps are carri
222. t inrange Then MsgBox Out of range Try again Loop Until Inrange End Sub This file parameters txt can be downloaded from the course web site byVal or byRef page 203 Q4 b byVal Q5 a byRef Q6 a byRef Q7 a byRef HERIOT WATT UNIVERSITY ANSWERS TOPIC 8 Designing the solution page 210 SWAP NUMBERS number number2 number number2 GET NUMBERS 1 getNumbers OUT Number 1 Number 2 2 Blanklines IN 3 3 Swap IN Numberi Number 2 Answers from page 211 Q8 b Repetition of lines of code are avoided Q9 d A footer Q10 b byRef is used for IN OUT parameters Q11 b Anything that happens to the formal parameter happens to the actual parameter Q12 c 56156 Turning a procedure into a function page 215 function getValidNumber as integer Dim numberOk as boolean Dim number as integer do number Inputbox Input a number numberOK number gt 0 if not numberOK then Print The number must be greater than 0 end if loop until numberOK getValidNumber number end function HERIOT WATT UNIVERSITY 255 256 ANSWERS TOPIC 8 Answers from page 215 Q13 c A function returns a single value Q14 c Square Q15 b y ABS 5 Program to Find Minimum page 226 Expected answer pseudocode set pointer to zero set minimum to first item in list Do increment pointer compare minimum to item at current position if item lt minimum then set minimum to item
223. t systematic and comprehensive testing 4 8 End of topic test An online assessment is provided to help you review this topic HERIOT WATT UNIVERSITY 60 TOPIC 4 PERSONNEL HERIOT WATT UNIVERSITY Topic 5 Languages and Environments Contents 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 INTFOCUCTION aieia be BAe Beda remet Ne eae UT BALERS Sa Programming Languages Classification of High Level Languages Procedural Imperative languages 5 4 1 Review Questions Declarative languages Event driven programs Scripting languages 5 7 1 5 7 2 5 7 3 5 7 4 5 7 5 5 7 6 Benefits of scripting languages Examples of Scripting Languages The need for scripting languages Greating a MaGro 44 3484 Ps ad eke a ea ee and tte Running A Macro s 4 45 4 Gt cee an at aa wee Soe BRU AA we af anc Review Questions Other Language Types Translation methods 5 9 1 5 9 2 5 9 3 Compilers and Interpreters Comparing compilers and interpreters Review Questions 2 4 4 4 ass arm mes ardent amp faa he 510
224. t testNumber is a single digit number Else PicDisplay Print testNumber is a double digit number End If Else PicDisplay Print testNumber is out of range End If End Sub Private Sub cmd_endProgram_Click End End Sub This file NestedlF txt can be downloaded from the course web site Code 15 Solution One variable testNumber is declared as an integer The user is prompted to enter a number between 1 and 99 and the value entered is stored in the variable number If the value is not within the specified range greater than 0 and less than 100 then the else part of the outer if statement is executed and the message Number is out of range is displayed on the screen and the program is finished On the other hand if the value is within range then the first part of the outer if statement is executed which contains several lines of code between if and End If Within this block of code is another if statement which tests if the number is less than 10 in which case the message single digit number is displayed on the screen otherwise else the message double digit number is displayed on the screen The program output is shown in Figure 6 15 HERIOT WATT UNIVERSITY 131 132 TOPIC 6 HIGH LEVEL LANGUAGE CONSTRUCTS 1 Formi Figure 6 15 Please take time to follow this explanation through If you can see the how and why of it you will be able to program if statements nested or plain without any
225. ta Tips Window Settings MV Drag and Drop Text Editing M Default to Full Module view IV Procedure Separator Figure 6 4 Here is the simple program to add 2 whole numbers illustrating proper declaration of variables Option Explicit Private Sub Form_load Dim FirstNumber As integer Dim SecondNumber As integer Dim Total As integer Dim MyText As string FirstNumber 5 SecondNumber 10 Total FirstNumber SecondNumber MyText Sample Program End Sub Code 7 HERIOT WATT UNIVERSITY 6 8 DECLARING CONSTANTS 103 Q8 What is wrong with this Visual BASIC program program subtract Dim numberi As Integer Dim result As integer numberi InputBox Please enter the first number number2 InputBox please enter the second number result numberi number2 Print Number 1 take away number 2 sum Calculating minutes Write a program which prompts the user to enter a number of days hours and minutes The program will then calculate and display this as a total number of minutes 20 min 6 8 Declaring constants A constant is a quantity that is allocated by the user usually at the start of a program although they can be defined anywhere in the program A constant retains the same value throughout program execution and cannot be altered Constants are declared using the const statement to create string or numeric values Examples of constant declarations are Const cPi As single 3 141592 Const
226. tal of the numbers 7 6 6 Do Until Loop The Do While loop performs the conditional test first and then executes the loop so the statements within a loop may never be executed The do until loop performs the statements first and then tests the condition This means that the body of the loop is always executed at least once This is the only difference but a significant one between these looping constructs The general form of ado until loop is Do Until test condition statements loop The statements in the body of the loop are executed repeatedly until the test condition is FALSE test condition rest of program Figure 7 9 HERIOT WATT UNIVERSITY 165 166 TOPIC 7 HIGH LEVEL LANGUAGE CONSTRUCTS 2 The do until loop is an example of a top tested while false structure The variant do loop until is an example of a bottom tested while false structure Do statements Loop until test condition The top tested loop can iterate between 0 and N times whereas the bottom tested loop may iterate between 1 and N This means that using the bottom tested loop the iteration must occur at least once so the condition can be tested immediately Some simple examples should clarify the situation Consider the simple lines of code representing a simple do until loop Dim Num As Integer Num 1 Do Until Num 10 Num Num 1 Loop MsgBox Num The equivalent do while loop would be Dim Num As Integer
227. teMain_Click They are re declared in sub procedure ExecuteLocal_Click and assigned new values Figure 6 9 shows the program output The program is called twice by activating the two buttons Formi In main program Testvariable 55 In main program TestString TestString Cal 1 gives TestVariable 0 Cal 1 gives TestString Cal 2 gives TestVariable 110 Cal 2 gives TestString Hello 2 Execute Public Figure 6 9 Public gives the original values that can change In call 1 local procedure resets the variables to 0 since they have been re declared HERIOT WATT UNIVERSITY 6 9 VARIABLES AND SCOPE 111 Call 2 produces the new values from the local procedure Therefore local variables always win Note Extensive use of global variables is bad practice the use of global variables should be kept to a minimum since their values can change from anywhere within a program as you have just seen Local variables on the other hand offer the following advantages 1 side effects caused by a subprogram altering the value of a variable used elsewhere in the program are greatly reduced 2 debugging is easier since access to variables is localised and so tracking errors can be faster 3 the transfer of procedures and functions from one program to another is simplified Sentence completion global and local variables On the Web is an interactivity You should now complete this task 6 9 1 Review Questions Q9
228. ten to put in the CD or the user entering a number when asked for a letter Reliability A reliable program always produces the expected result when given the expected input It is designed correctly to do the task specified Characteristic of good software design On the Web is an interactivity You should now complete this task 2 8 2 Review questions Q19 Choose the correct response that describes the term robust within software development a The program is strong and hardy b The program may be ported to a different machine architecture c The program can cope with mistakes that the user might make HERIOT WATT UNIVERSITY 2 9 MAINTENANCE 31 d The program runs to specification Q20 Choose the correct response that describes the term reliable within software development The program is strong and hardy The program may be ported to a different machine architecture The program can cope with mistakes that the user might make The program runs to specification a b c d Q21 Using a module library can reduce software development time because choose one a Common programming modules can be used b Programmers do not need to write programs from scratch c Programmers can re use library code in their projects d All of the above 2 9 Maintenance Once the software is operating the users will need support In the case of a bespoke system the development team or the organisation it works for may offer
229. the if statement The next condition tests the variable number to see if it is greater than or equal to 10 If this is true then you know the variable number has a value between 10 and 99 and so it must have 2 digits and the variable n_digits is set to 2 Again if this condition is not fulfilled then you move onto the next branch of the if statement The next condition tests the variable number to see if it greater than or equal to 0 If this is true then you know that the variable number has a value between 0 and 9 and so it must have one digit The variable n_digits is set to 1 The next branch of the if statement is not an elseif branch but an else branch and so does not have a condition but is the branch that is executed if none of the other conditions are met Execution of this branch of the if statement results in the message Value out of range being displayed on the screen Example 2 Grades and Marks Problem Write a program using the ElseIf construct for a user to input a test result and output the corresponding grade Test scores range from 0 to 100 and the grades from A being the highest to E the lowest Solution Use the following algorithm 1 ask user to input a mark between O and 100 2 If mark gt 0 and lt 30 then grade E 3 elseIf mark gt 30 and lt 49 then grade D 4 elseif mark gt 49 and lt 65 then grade C 5 elseif mark gt 65 and lt 85 then grade B 6 elseif mark gt 85 and l
230. the interpreter executes each line of code at a time the programmer is able to see the results of their programs immediately which can also help with debugging HERIOT WATT UNIVERSITY 5 9 TRANSLATION METHODS 5 9 2 Comparing compilers and interpreters Efficiency The main difference between an interpreter and a compiler is that compilation requires analysis and the generation of machine code only once whereas an interpreter may need to analyse and interpret the same program statements each time it meets them e g instructions appearing within a loop For example consider the following Visual BASIC code For iCountvar To 20 iSum iSum iCountvar Pic Display iSum Next iCountvar Using a compiler the source code would be analysed and compiled into machine code once only Using an interpreter the source code would be converted into machine code 200 times once each time round the loop Errors This has implications for error reporting For instance when the interpreter encounters an error it reports this to the user immediately and halts further execution of the program Such instant feedback pinpointing the exact location of the error helps the programmer to find and remove errors Compilers on the other hand analyse the entire program taking note of where errors have occurred and places these in an error diagnostic file If errors have occurred then the program cannot run Programmers must then use the error messa
231. ther another condition is already True such as If its 6 30 p m and if I m logged on to SCHOLAR then nested If statements can be used A nested If statement is one that s enclosed within another If statement The format for a nested If statement is as follows If condition Then If another_condition Then statement Else another statement End If End If if statements can be nested but care should always be taken to ensure that the else statement is associated with the correct if Nested IF statements can be avoided by using the Select Case statement which is described in a later topic The following example exemplifies the nested f statement Example 1 Testing for range and the number of digits in a number Problem Describe the operation of the following program as seen in Code 15 Option Explicit Private Sub Commandi_Click program nested_IF 15th February 2004 HERIOT WATT UNIVERSITY 6 15 OTHER FORMS OF IF STATEMENT gt Program by Fred Fink This program will prompt the user to enter a number between 1 and 99 The program will test the number to see if it is less than 10 and print the message that it is a single digit number If it is gt 9 it will output double integer number otherwise out of range Dim testNumber As Integer testNumber InputBox Please input a number between 1 and 99 If testNumber gt 0 And testNumber lt 99 Then If testNumber lt 10 Then PicDisplay Prin
232. therwise it will diverted elsewhere c Give the users in the company something else to do d Benefit the organisation in some way Q3 Which one of the following statements is NOT true of the systems analyst a The systems analyst is appointed by the project manager b The systems analyst discusses the system requirements with the clients c The systems analyst determines the exact nature of the problem d The systems analyst is responsible for the entire project Q4 The purpose of the systems analysis is to a Allow the systems analyst to produce a clear specification of the problem b Allow the client to say how much the project will cost c Allow the project manager to dictate whether the project should go ahead d Allow the collection of information that the company will need anyway Q5 Ifa project falls behind schedule who is responsible for getting it back on track The client The project manager The systems analyst The project will eventually recover itself Q 0 9 HERIOT WATT UNIVERSITY 56 TOPIC 4 PERSONNEL 4 5 The Programming Team The programming team is responsible for the implementation phase of the software development process They work to the design created by the systems analyst They are also responsible for testing the software and for maintaining it once it has been installed The team will report to the systems analyst ff First the detailed logic of the modules in the syst
233. tore 1 Print element 2 Store 2 Print element 3 Store 3 Print element 4 Store 4 Print element 5 Store 5 A single element can be displayed or accessed at random you are not forced to process the entire array to do this Any one of the six lines of code above does the job of printing out that particular array element so the code Print element 5 Score 5 outputs the sixth element of the array the first element being element 0 Example 3 Reading user input into an array Problem How can data entered by the user at the keyboard be stored directly into the elements of an array Solution Consider the situation where you want to store 4 user entered integers in an array called mark You could use a for next loop to prompt and obtain input and to store the integers in the array e g for times 0 to 3 mark times InputBox Please input marks next times For each loop the user will be asked to input a mark After four marks have been entered the loop will terminate and the array mark will be storing the four value Using arrays Several examples using arrays have been illustrated in the course notes Incorporate these program fragments into a working program which can do three things 1 initialise each element of an array to zero 2 allow you to input data in the form of floating point numbers directly into the array 3 print out the contents of the array Try to make the program user friend
234. training in the use of the new system Creators of software systems often establish help desks so users can obtain advice about the software Software does not wear out in any physical sense but the presence of errors or omissions will give rise to the need for maintenance This doesn t appear to be working HERIOT WATT UNIVERSITY 32 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS Software maintenance always involves a change in the software with the accompanying probability that additional errors may be introduced It is essential to ensure that adequate quality control is in place There are three types of software maintenance corrective adaptive perfective Corrective maintenance is concerned with errors that escaped detection during testing but which occur during actual use of the program Users are encouraged to complete an error report stating the inputs that seemed to provoke the problem and any messages that the program might have displayed These error reports are invaluable to the development team who will attempt to replicate the errors and provide a improved solution Adaptive maintenance is necessary when the program s environment changes lt allows the authors to provide a program which responds to changes in the operating environment For example a change of operating system could require changes in the program or a new printer might call for a new printer driver to be added t
235. ttempt now Example 1 Passwords Problem A program is written which asks the user to enter a password and to confirm it by entering it again If both words are equal to a program constant then the program HERIOT WATT UNIVERSITY 6 14 COMPARISON OPERATORS 125 will display a suitable comment If not or only one instance of the password is entered the user will be informed The algorithm is shown below Solution request ist password from the user request 2nd password from the user if the first password constant and the second password constant then display the word entered both times else display the two words and that they are different OO O1 amp WN FB The full Visual BASIC code for this program is as follows Option Explicit Private Sub Commandi_Click program using the AND operator 15th February 2004 Program by Fred Fink gt This program will prompt the user to enter two words and compare them to a string constant Dim Wordi As String Dim Word2 As String Const pass As String Daffodil Wordi InputBox Please input password Word2 InputBox Password again please If Wordi pass And Word2 pass Then PicDisplay Print Both words pass are identical Else PicDisplay Print Wordi and Word2 are not identical End If End Sub Private Sub cmd_Exit_Click End End Sub This file Password txt can be downloaded from the course web site Code 13 HER
236. uce a value parameter to make the procedure much more flexible Here is the Visual BASIC code Code 32 Private Sub Command_Click Modified program lines Print Message 1 HERIOT WATT UNIVERSITY 204 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Call BlankLines 5 Print Message 1 End Sub Private Sub BlankLines ByVal Number as Integer Dim count As Integer For count 1 To Number Print Next Count End Sub Code 32 The actual parameter is 5 the formal parameter is Number By calling Blanklines 5 the actual parameter 5 is passed into the formal parameter Number in the procedure The procedure code is executed with Number 5 then it terminates Note that the formal parameter is preceded by the Visual BASIC keyword ByVal to indicate a value parameter It is essential to declare whether the parameter is called by value or by reference The following worked example will help you understand passing by value Example 1 Use of procedures with value parameters Problem Write a program that outputs the square and square root of a number that is input by the user This number will be passed to each of the procedures Solution The following algorithm uses two procedures with value parameters 1 set up variables 2 get valid user input 3 call subprogram square 4 call subprogram sqrRoot The full Visual BASIC program is shown in Code 33 Option Explicit Private Sub Commandi_Click
237. uirements specification e the system specification or software specification HERIOT WATT UNIVERSITY 4 4 THE SYSTEMS ANALYST 55 The specification includes a full description of the problem All the inputs processes and outputs are described No system works on its own independently of the outside world certain assumptions have to be made about the boundaries between a system and its environment and these must be indicated described and included The specification represents a legal agreement between the clients and the development team The process of reaching agreement will be iterative the analyst will present a draft specification to the clients who will suggest amendments and so on until a specification is agreed The specification is used throughout the rest of the development process Material produced is based on it and compared with it For example test data will be drawn up on the basis of the specification The specification can be used as a checklist to ensure that the development process remains on target 4 4 3 Review Questions Q1 Inthe development process the client is best described as choose one a The group who will use the software b The group who will test the software c The group who will purchase the software d The group who will write the software Q2 In a company the idea of starting a new project is mainly to a Make as large a profit as possible b Use up surplus capital o
238. ulminates in an operational requirements specification When the operational requirements have been agreed by both the consultants and the customer a contract for the system is drawn up The Systems Analyst develops a design for the solution The consultants put a team of programmers on the job to code the design and the software development process begins Once the software has been implemented in a chosen language it undergoes rigorous testing by an independent test group Identifying Personnel involved in a Systems Development On the Web is an interactivity You should now complete this task HERIOT WATT UNIVERSITY 4 2 THE CLIENT 4 2 The Client In a software development project the client is the person or organisation which requires the new software to be developed The client might be a major multinational company a government department a small company a charity an individual It is important to note that the terms client and user do not necessarily mean the same thing but are sometimes used interchangeably A client is someone or a group such as management who buys or intends to buy some software for a particular purpose A user is someone who uses or will use the software The appropriate personnel within the client organisation will be concerned with the following activities e holding discussions with the consultants e reviewing reports and negotiating contracts providin
239. umber as integer as integer double number 2 end function The function would then be called as new_value double 10 We could combine this in a section of a program with a procedure to get a valid positive number gt Program getNumbers Dim number integer getValidNumber number print Twice that is double number sub procedure getValidNumber ByRef number as integer do HERIOT WATT UNIVERSITY 213 214 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS number inputbox Enter a number loop until number gt 0 end sub function double number as integer as integer double number 2 end function Simple Doubler Code the above section of code into a Visual BASIC program and run it with different values 8 3 3 User defined Function Examples Example 1 Area of a Circle A program has to be written that uses a function to output the area of a circle given the radius Solution We will use the following algorithm 1 display table headers 2 For each radius 3 Print radius and area 4 Next radius The Visual BASIC program is seen in Code 36 Option Explicit Const Pi As Single 3 141592 Private Sub Commandi_Click Dim Radius As Integer PicResult Print Tab 4 Radius Tab 16 Area PicResult Print For Radius 1 To 10 PicResult Print Tab 6 Radius Tab 16 Format Area Radius Next Radius End Sub Function Area Radius As Single gt This function will calculate area of
240. urce code 2 6 Testing Testing has several purposes It should check that e the software meets the specification design e itis robust e itis reliable testing documentation evaluation maintenance Commercial software is not exhaustively tested at the testing stage Software can be complicated and the available time is limited There must be a balance between creating a product for the market and exhaustive testing If errors become apparent after release the company will fix them and release an updated version Testing follows a test plan or strategy involving carefully selected test data with a view to ensuring that a reliable product has been constructed Important aspects would be e what part of the program is being tested e what is the expected output using suitable test data Testing is carried out at several stages during and after implementation HERIOT WATT UNIVERSITY 24 TOPIC 2 FEATURES OF SOFTWARE DEVELOPMENT PROCESS Unit Testing Module Testing Sub system Testing Integration Testing Acceptance Testing 2 6 1 Test data preparation Testing can never show that a program is correct Even with extensive testing it is almost certain that undetected errors exist Testing can only demonstrate the presence of errors it cannot demonstrate their absence Tests should be devised against the specification so that you can see whether or not the p
241. ure then make it a value parameter if a parameter represents a result that is produced by the procedure to be used elsewhere in the program then make it a reference parameter Note Call by reference is the default condition for Visual BASIC but for Visual BASIC Net users the default condition is call by value 8 2 1 7 Program using reference parameters Problem A user enters two numbers at the keyboard Write a program that swaps the positions of the numbers Design The program will use 3 procedures as shown in the pseudocode 1 GetNumbers Number1 Number2 2 BlankLines 2 3 swap Number1 Number2 Notice that we are using the procedure BlankLines the first procedure we met at the start HERIOT WATT UNIVERSITY 210 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS Designing the solution 1 Draw a structure diagram 2 Show by arrows the flow of data in and out of the procedures getNumbers and Swap 3 Complete the pseudocode showing the IN and OUT parameters for each procedure Implementation The full Visual BASIC program is shown in Code 35 Option Explicit Private Sub Exchange_Click Dim Numberi As Integer Number2 As Integer GetNumbers Numberi Number2 BlankLines 2 swap Number1 Number2 End Sub Private Sub BlankLines ByVal Num As Integer Dim count As Integer For count 1 To Num Display Print Next count End Sub Private Sub swap ByRef valuei As Integer ByRef value2 As Integer D
242. very user s directory on iterate thisFolder tell application Finder if the count of folders in thisFolder gt O then repeat with innerFolder in every folder of thisFolder as list if file Mail Drop Preferences of innerFolder exists then delete file Mail Drop Preferences of innerFolder end if if file Email Startup of innerFolder exists then delete file Email Startup of innerFolder end if if file EmailSavePreferences of innerFolder exists then delete file EmailSavePreferences of innerFolder end if end repeat end if HERIOT WATT UNIVERSITY 74 TOPIC 5 LANGUAGES AND ENVIRONMENTS end tell end iterate Code 3 JavaScript is a well known scripting language that allows more functionality and enhancement to be added to web pages JavaScript code can run on any platform that has a JavaScript interpreter which includes most browsers Typical uses of JavaScript include a Image or text rollovers If the user rolls the mouse over a graphic or hypertext then a text or graphic box will appear http scholar hw ac uk heriotwatt scholar2003 courses higher computing Unit2 glossary asp 42 JavaScript Text CTRL click to follow link Creating a pop up window to display information in a separate window from the Web page that triggered it This is useful if the user requires to perform a simple calculation or consult a calendar for inputting dates This is achieved by embedding ActiveX controls or Java app
243. w to try out various settings and captions for the buttons and settings for the text box and form Exercise 2 Open a new Visual BASIC project and produce the following form that shows text boxes labels and buttons Use the properties window to create captions for the objects Number addition END Program HERIOT WATT UNIVERSITY 6 3 BUILDING APPLICATIONS 91 6 3 5 Output Methods In Visual BASIC there are many ways of outputting data We will only consider two of these using the MsgBox function e using the Print command 6 3 5 1 The MsgBox A message box allows the program to display any message to the user in a pop up window on screen The MsgBox function is useful in situations where the user requires for example to confirm an action In its simplest form the format of the function is MsgBox The value entered was within the required range The output screen would look like The full format of the MsgBox statement is MsgBox Prompt Buttons Title Prompt is the message to be displayed in the MsgBox Buttons is a numeric expression that specifies which buttons to display with or without icons Title The string message displayed in the title bar Exercise 3 Experiment with MsgBox button values and create your own messages 6 3 5 2 The Print command The print statement is a useful output command since it can be used on its own or in combination with other objects and functions Us
244. ware development process will be obvious Without this understanding it is all too easy to dismiss the software development process as a not very useful exercise but one which will give you a Higher credit 1 2 Real life programs and classroom programming What are the differences between the two Table 1 1 should give you an indication Table 1 1 Real programs vs classroom programs Real life Programs Classroom programs Sc ope are large and complex It is are small and simple They can difficult to hold their details in your be described in a few sentences mind Because of this you have to and probably understood in specify them formally minutes Difficulties The main difficulty is with a The main difficulty you have is with understanding the problem b writing the solution in a ensuring that your understanding programming language which you actually matches the users are just learning and getting your requirements c designing a program to work correctly solution Development Development time is long Maybe Development time is short You time as long as 5 years It is impossible should be able to get the core of to remember all aspects of a the solution working in a few hours program for this length of time so Consequently you can hold details you have to document the design of all aspects of the program in decisions and all your changes your head Documentation is skimpy or non existent Testi
245. y using such code instead of re inventing the wheel Procedures and functions are somewhat similar in their structure They both consist of e a heading e a declaration part where necessary an action part a compound statement A typical Procedure Sub getValidNumber ByRef number As integer Dim numberOk As boolean do Print Input a number numberOk number gt 0 if not numberOk then print The number must be greater than 0 end if loop until numberOk End sub A typical Function function getValidNumber As integer Dim numberOk As boolean Dim number As Integer do print Input a number numberOk number gt 0 if not numberOk then print The number must be greater than 0 end if loop until number0k getValidNumber number end function A procedure or function is activated by a call from the main program after which the procedure or function executes its block of code and then terminates The flow of data between procedures functions and the main program block is accomplished by the use of parameters which will be discussed later HERIOT WATT UNIVERSITY 196 TOPIC 8 PROCEDURES FUNCTIONS AND STANDARD ALGORITHMS 8 2 1 Procedures Visual BASIC offers a variety of procedure types The two that concern us here are event procedures general procedures Up to now most of the programming code you have seen has been made up of event procedures that activate sections of code when
246. ystem Previous output becomes new input Fit for purpose The finished program runs to specification and is robust and reliable Fixed loop A control construct which allows a block of code to be repeated a number of times set by the programmer in advance Fixed loops These loops iterate a fixed number of times Function A block of code like a procedure but a value is returned when the function is used Functional language A language that utilises the evaluation of expressions rather than the execution of commands It is based on the use of functions from which new functions can be created Functional specification This will detail how the developed program will behave under specified conditions General purpose language The language can be used to program solutions covering a broad range of situations HERIOT WATT UNIVERSITY 234 GLOSSARY High level language A language designed to be easily understood by programmers They use commands and instructions based on English words or phrases Human computer interface Allows the program to interact with the outside world The interface is the only part of the program that users see Implicit declaration If a variable for example is not fully declared by the user then it is given default attributes by the Visual BASIC language Independent test group Testing of software by a group out with the development team Inheritance The sharing of characteristics between a class of

SQA Higher Computing Unit 2: Software Development

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