Home

PROGRAMMING

1. WHILE ENDWHILE for a variable number of repetitions with the possibility that the process might not be executed even once Entry checked at the beginning e Applying loops in common standard situations i Looking at all elements of an array of all records in a serial sequential file e g valuation of all items held in the file ii Searching for a particular element in an array or serial sequential file stopping the search if found or reporting that the search has failed if the element has not been found when the end of the array is reached iii Search one array for a target value and if found displaying a corresponding value from another array which may hold data of a different type iv Using double loops one embedded in another e g invoicing a number of customers each buying a number of different products Structuring program by means of a top down approach in particular using procedures Writing and using procedures with input parameters Using standard functions as listed in the syllabus including string functions Writing and using own functions to perform simple tasks e g accepting three integers and returning the middle valued number e Setting up menus accepting the user choice and executing the appropriate action e Validation of data for range or within a particular set TESTING Candidates will be expected to write about the process of testing and the design of test data They must be aware of the four elements o
2. one page this may mean there are page totals which are then carried forward This extra data can clearly be simple data as in iii above Testing This is the actual testing It clearly does not form a part of the examination but will be tested theoretically Candidates should be aware of the different types of testing possible These are i Dry Run Candidates WILL be expected to perform a dry run on an algorithm with given data This should be set out in table format with one column for each variable in the routine Each row of the table should show the progress as data passes through the routine Only when the value of a variable changes should there be an entry in the table Leave blank spaces on each row for each variable which does NOT change WWW ICM AC UK ii Module testing iii Program testing iv Link system tests where the file outputs from one program are input into another v Live data testing vi Acceptance testing the user supplies data monitors the outcomes and accepts the programs as they are or requires the programmers to correct some problem area IT DOES NOT WORK A frustrating situation for any programmer is to obtain faulty outputs and the programmer after much dry running and testing has no idea where the error is Candidates frequently suggest asking another programmer to check but this is ignoring the issue A professional programmer should be able to deal with it Possible solutions are e Using a
3. trace program which will display the values of variables at different points in the run and hence give the programmer a better idea of where the problem is e Similarly the programmer can insert his her own test bed routines These are small coding routines perhaps a procedure which can be inserted anywhere in the program to print out variable values at that point These routines are often de activated but left in programs for the benefit of subsequent maintenance programmers 4 TestLog A programmer should record details of every test undertaken This will show i date time ii which set of test data was used i purpose of the test perhaps the menu option being tested ii outcome briefly describe what is successful and what is not iii possible actions or causes of any problems e g variable X should be validated to be 1 to 10 Candidates undertaking the Programming Project sometimes give the impression that everything worked first time We all know that did not happen Admitting problems is a professional approach and indicates that the candidate knows how to proceed Not admitting the problem is actually missing out part of the required project work and will inevitably earn fewer marks DEVELOPMENT PROGRAMMERS MAINTENACE PROGRAMMERS Candidates must know the roles of the programming team in a professional situation Of course it varies depending on the size of the new application and the way the application is being impleme
4. WWW ICM AC UK PROGRAMMING TUTORS These notes are designed to assist teachers of the course and are in a condensed format Teachers should also consult the syllabus for this module and adapt these notes accordingly by using extra examples and by filling out this material with detail Students will be expected to apply the material in a BUSINESS environment and with reference to the particular situation specified in the examination question Repeating these or any other notes in a generalised form is unlikely to satisfy the required answers for any question PRACTICAL REQUIREMENTS Students are expected to have worked in a high level procedural language Centres can choose the language but it is essential that it offers all the features listed within this section These notes will not cover the language teaching elements because this is best achieved using a suitable manual or textbook devoted to that language PROGRAMMING METHOD e Candidates must be familiar a formal algorithmic method of representing logic Ideally PSEUDO CODE is suited for learner programmers because of its compactness Other methods such Flowcharting Jackson Charts are acceptable Whichever method is used it must have a standard format e Suggested layouts for Pseudo code the examples are only intended to illustrate each type and do not represent a solution to a particular problem Input ProductID QuantityOrdered ltemCost QuantityOrdered x UnitPrice Out
5. are not exact round numbers to ensure the print layouts are correct particularly with money values However this need only occur a minimum number of times Data testing for other features can be simpler e g customer orders 2 items at 10 each iv that all arithmetic processes are checked Two examples where data may appear to give the right answers but the logic could be wrong are a Multipliers e g Ensure at least one customer orders two or more items of a given product otherwise a cost of 1 x 17 50 17 50 could have been achieved merely by using the price b 2x2 2 2 Two items at 2 cost 4 but a program error with the x accidentally replaced by a will not show this error Instead check with 2 x 3 or other combinations v that all possible repeating situation occurs e g for a customer ordering system a There are at least two customers in the data b Some customers order only 1 product while others order several products Expected Results This feature is often overlooked Write out the expected results for the complete set of test data All subsequent tests will be compared with these results If the data is good enough to test the program rigorously there should be no need to devise new test data later Bulk Data Test data should never be excessive There is no need to test a particular situation more than once However there is a need sometimes to produce more data simply to ensure that outputs run to more than
6. f testing 1 Test Plan This is the devising of an overall strategy about how to go about the testing Consider the simple example of a program controlled by a menu with the following menu options there would be other options Add new customer Delete customer Amend customer Access and display a customer s details Display all customer balances End Program A test plan would probably be i Check the menu system works Options 1 to 5 and 0 The menu and all procedures need to be in place Each procedure only displays an identifying message to show that it has been accessed the screen held and then return to the menu At this stage NONE of the main procedures perform their required task but the structure is fully in place and the program will run for any option even if it does nothing useful i Options 1 and 5 New customers are added and proved to be on file by option 5 which displays some details for ALL customer onRWND WWW ICM AC UK iii Option 3 Customer details changed address telephone credit rating and checked by option 5 iv Option 4 This could be combined with 3 so that a customer s details are displayed with option 4 altered with option 3 and then checked with option 4 v Option 2 Finally this option is written and checked with 4 or 5 It is pointless trying this earlier because the program needs a minimum amount of data on file to be checked and to start deleting it before other options are fin
7. ished is unhelpful vi Bulk data This is additional data for no other purpose than to check that the program can handle more output than can appear on one screen or one page The decision when to test VALID and INVALIDATE situations varies with type of problem It is usually beneficial to check the program works with valid data before starting to enter invalid situation Test Data Test data needs to be carefully designed Its purpose is not to check that the program works but that it does not fail If a program is tested with minimum data it may appear to work but because certain situations have not been checked logic errors are not seen until that data situation appears later possibly when the program is running live Test data should check i valid and invalid situation Checking for wrong data type is more advanced and is not expected at this level The question will state this boundary conditions e g if better discounts are offered when a customer spends 100 and again at 200 extensive test data is needed Spending totals of 99 99 100 00 199 99 200 00 should be tested The first pair show not only that a better discount is earned at 100 but that it occurs at EXACTLY 100 Testing with 50 150 and 250 WILL give different discounts but these figures do not prove that the changeover occurs exactly at 100 and 200 ii decimal values for real data In designing test data there needs to be some totals which
8. ithin that routine OR in routines called by it ii Global Variables Their values are available throughout the whole program e Automatic file dumps activated by program This is a security process to ensure that main files are saved at frequent time intervals during a long run along with the current state of certain memory registers If the program fails before the next dump the data can be recreated and accurate to the last dump This overcomes the problem of lengthy file update print run failing perhaps because of a printer failure The program is effectively run from the point of the last dump ensuring that all printouts are produced and the file is correct WWW ICM AC UK Iterative Solutions_ Scientific mathematical problems often do not have a known method of solution An example is a complex equation A repetitive method is used where an initial estimated solution is input and a better solution is produced at each phase until successive solutions are within the required accuracy This is ideal for a computer which is able to repeat a process thousands of times per second and work to many digits of accuracy The accuracy required is input The problem is that in some cases unless the initial estimate is close enough instead of converging on an answer the program diverges or converges onto an alternative solution which is not required Candidates are not expected to know the theory of iterative processes but could be asked to progra
9. l an exit condition is met Construct routine with ONE entry and ONE exit Sequence construct grouping the steps of the tasks one after the other Iteration Selection construct performing different tasks according to a condition WWW ICM AC UK Note that Iteration and Selection Constructs must still have one entry one exit It is not permitted to exit the construct from within a loop REQUIRED PROFICIENCES by students e Defining variables and assigning appropriate data types e Input of data from a keyboard including a suitable prompting message e Outputting data to screen and printer with good layouts This includes tabulating data so that decimal points align output of numeric data to a specified number of decimal places e Manipulating string data including extracting parts of a string using appropriate string functions e Choosing the most appropriate data structure strings arrays records e Applying decision instructions IF CASE with multiple actions in any of the resulting action sections e Recognising the need for a loop and deciding which to use Generally this means the ability to use i FOR ENDFOR to control the repeated process a fixed number of times Defining the loop control count variable and incrementing it appropriately by 1 1 or other intervals ii REPEAT UNTIL for a variable number of repetitions which will always occur AT LEAST ONCE Exit from the loop is at the end iii
10. m one where the details are given in the question
11. nted database A general process which would cover most situations where some parts could be omitted is Systems analyst gives a presentation to the whole programming team on the overall purpose of the new system and its common processes 2 He then gives each programmer an individual program specification 3 After reading the specification the programmer may need a 1 1 meeting with the analyst to clarify certain elements 4 Programmer designs test data and expected results Sometimes the analyst provides this Programmer and analyst discuss the testing plan Designing test data early helps to identify the situations that can occur 5 Programmer develops an algorithm 6 Dry run test data through algorithm and compares with expected results 7 As a result of the dry run some changes may need to be made 8 The program is coded into the language dictated by the analyst 9 The program is compiled and syntax errors corrected 10 The program is tested using the same test data and compared with expected results A test log is maintained 11 System and Acceptance testing with the user is undertaken the programmer may be present 12 Throughout the programmer maintains documentation inclusion in the final documentation 13 A user manual is produced A technical manual is produced for the maintenance programmer 14 After acceptance where all programs are completed and working the programming remains on standby for a limited period
12. put GrossTotal VAT NettTotal 3lines 2dp If ItemCost gt 100 then DiscountRate 5 else DiscountRate lt 0 Endlf For Count 1 to 12 process for each month EndFor Repeat process next ordered item Until ProductID 0 While StockLevel gt 0 process this order EndWhile Open File filename Input or Output Close File name or ALL Read filename record Write filename record Data input at keyboard Calculation Output with editing notes Decision note indentations Loop Fixed number of repeats Indentation of the repeated process Loop Variable repeats BUT at least once Loop Variable repeats BUT may not enter first time Open a file Close 1 or all files Read record from particular file Write to a file recordname fieldname can used for individual fields of the record T row column 2 D Array access row column could vary within a double FOR loop The use of indentation as shown above is essential for easy visualisation and to assist during development e Top Down Breaking problems into major parts which are then subdivided into more detailed logic Enables modules can be tested separately and errors pinpointed to precise locations Modules can be written by different people and reused e Structure Programming is the step wise refinement top down approach breaking the problem into blocks called CONSTRUCTS There are 3 main structures construct repeating a series of tasks unti
13. rstands what to do in every situation This includes knowing what options the system offers possible restrictions e g salesmen have access only to certain elements of the system how to run the program how to install possibly but this may be restricted more technical staff possible problems and what to do when they arise Maintenance Programmer He she would have access to all the user documentation but would prefer more compact information The four items above would be at his disposal with details of how the whole system links together ERRORS 1 Syntax errors Violations of the language rules e g Misspelling a key word such as PRINT The compiler detects the error 2 Technical errors during the compilation process The compiler manual probably needs to be consulted 3 Logic errors Errors which produce the wrong results as shown up by comparing actual with expected results 4 Runtime errors Errors which stop the program completing The computer is unable to continue The simplest is Divide by Zero The programmer will not have written an instruction actually doing this but may have coded A B and B might happen to be zero under certain conditions OTHER IMPORTANT FEATURES e Parameter is a value passed to or from a routine indicating how that routine will perform e g A or D indicating whether a sort is to be ascending or descending Procedures Functions use i Local Variables Their values are only valid w
14. to effect immediate corrections when the system is running live Each programmer will probably now be also beginning for a new project 15 When problems seem to have been corrected the team disbands If the team consisted of 10 programmers only a small number of these perhaps even will then be designated as WWW ICM AC UK maintenance programmers for the whole system This means a programmer will be expected to make corrections on some programs that he she did not actually develop 16 After reviews perhaps at 6 months 1 year changes may be needed for business legal reasons and the maintenance programmer will implement these If the maintenance program leaves the company then a replacement should be appointed immediately because of the need for somebody always to be knowledgeable and available at short notice in the event of an emergency business must still keep going DOCUMENTATION All elements of a business program must be retained as part of the documentation The candidate needs to know which parts will be used by the maintenance programmer and which will be for the user User Users are NOT programmers and are not expected nor should be allowed to make changes to programs Hence all elements of the logic should NOT be available to the user This includes i Algorithm ii Annotated listing of the code iii Variables list iv Original Test data The user needs documentation at a simple level to ensure that he she unde

PROGRAMMING

Contents

Download Pdf Manuals

Related Search

Related Contents