SECTION I - Using C++
Contents
1. function prototypes constants global variables int main program statements go here return 0 end of main function You can use this template to begin all of your coding projects where some of the code is not provided A consistent look for all of your programs shows good coding discipline Using a proper structure indenting consistent use of upper case and lower case can make your programming easier to debug for you and anyone who needs to maintain your code at a later date Lesson 1 9 Summary C is a widely used programming language which makes it an important language for a programmer to master The programmer should understand the steps to completing a C programming project as well as the way a C compiler goes about creating an executable file A good C program should be properly commented spaced and indented mainly for ease of maintenance Good programming style usually indicates a well structured program CHAPTER 2 Problem Solving I Objectives Describe the tools available to plan a programming task List the symbols used in flowcharting and their meaning Explain how to use pseudocode to plan a programming task Create an IPO chart to solve a programming problem Define the steps in creating an IPO chart Lesson 2 1 Problem Solving The ability to solve word problems is perhaps the most important tool in the programmers toolbox Every program begins as a word problem Some2. Always required The section of the program under Declare Variables has three entries We declare the variable Y and give it a value of 3 a variable called Z and give it a value of 2 and a variable called X and give it a value of 0 because we do not know the result of the calculation yet A variable is a chunk of memory that is allocated by the program to store a value The value may or may not be known at the time the program is written The value stored in a variable may be changed in the course of the program execution You give that chunk of memory a name so your program can reference the correct area of memory to get the correct value for its calculation The section of the program under Calculation shows the calculation of adding the amount stored in Y to the amount stored in Z and putting the result in the variable X The expression to the right of the equal sign assignment operator is evaluated left to right and when complete the result is stored in the variable to the left of the equal sign assignment operator Lesson 3 2 Real World Example Now let s put a real life situation to this equation John has 3 Apples Mary has 2 Apples if they give all their apples to Mom how many Apples will Mom have From this problem we develop an equation Mom s Apples John s Apples Mary s Apples Our IPO chart should look like this I P O Johns Apples 3 Marys Apples 2 add Johns apples to Marys apples giving
3. Moms apples Moms Apples Or in our example program from above lt p gt Apples cpp This is a sample program int main Declare Variables int JohnApples int MaryApples int MomApples 0 3 2 Calculation MomApples JohnApples MaryApples The variable MomApples has now been assigned the value of JohnApples plus the value of MaryApples return 0 End of Main Function We use exactly the same program but give the variables more explicit names The program simply takes the values stored in JohnApples and the value stored in MaryApples adds the values together and puts the sum in the variable called MomApples At the end of this process the contents of the chunk of memory assigned to each variable will look like Chunk called JohnApples Chunk called MaryApples Chunk called MomApples Lesson 3 3 A Complex Problem Now we are ready to tackle an even more complex problem You purchase a new text book for 79 95 and the sales tax is 5 You pay for the book with a 100 bill How much change will you receive from this transaction Again we must first develop the formula or algorithm for solving this problem It will really consist of several steps of formulas with the answer from one providing the data for subsequent steps We need a little more work on our IPO chart here to produce a chart that accurately reflects what we need to accomplish First
4. It is merely writing down the steps to solve the problem in the correct and logical order The process is similar to doing an outline before you write a report It helps you organize your thoughts on writing the applications There are no keywords or specific syntax for the pseudocode Pseudocode for a problem requiring the solution to the simple interest algorithm Interest Principal Times Rate Times Term may be expressed in pseudocode as follows 1 Ask the user for the principal amount 2 Ask the user for the interest rate as a decimal 3 Ask the user for the length of the loan in years 4 Calculate the Interest by multiplying the principal times the rate and the result of that by the term of the loan 5 Display the annual interest for the loan These simple sentences outline a step by step process for solving the algorithm Lesson 2 5 IPO Charts Creating an IPO chart to analyze your program can eliminate many problems when you are ready to code IPO is an acronym for Input Processing and Output Each letter represents a column in this three column form First column lists the variables for the Inputs the second column shows any processing items variables created within the code as well as the pseudocode or flowchart used to solve the problem The third column list the variables that are to be output When using the IPO chart you must first analyze the word problem and find out what is the goal or the output or the answer to the
5. PC It is an Open Source offering so it is the full version that will not expire or will you ever be asked to make any purchase There is limited support available on the internet gcc Compiler The gcc compiler is included in almost every Linux Operating System implementation C is widely used in the Linux community for software development Many of the applications available for the Linux operating system were written in C and many require compilation before they can be used Lesson1 5 Compiling a Program Create Source Code Enter the code required to solve the problem This is a plain text file that consists of the C framework containing C commands These commands are stored in a file with a cpp extension Compile the Code The compiler turns the source code into the ones and zeros that the computer understands This is then written to a file with an obj extension Link in the Libraries Some commands we use in C require additional code to complete their function This code is stored in files called libraries This is tested code that you benefit from because it can greatly reduce the number of commands you need to write by using pre written and tested code The result of this process is a file with a exe extension Executable Once you have an executable file it can then be transported to any other PC with a suitable operating system and run just as well as it did on the computer that created it Note that programs created by
6. Visual C will require that the computer running the executable has the current NET framework installed Finding Files When you have everything working you may want to find the source and executable files By default Microsoft puts a project folder in the Project folder within the Visual Studio folder found in the user s document folder There are several sub folders in the project folder and depending on the version the cpp source and exe executable will be found in one of these folders Lesson 1 6 The Programming Process Understand the Problem Before the programmer can do anything they must have a solid understanding of the problem to be solved by the computer program they are about to create Analysis The programmer must break the problem down into the logical steps and algorithms required to solve the problem This is generally accomplished with flowcharts pseudocode IPO charts and other analysis tools Code This is the step where the programmer writes the source code to solve the application problem When coding is complete the programmer compiles the program fixes any errors and repeats the process until the compiler can produce an executable file Test Now that we have an executable file the programmer must make sure the program produces accurate and consistent results There should be a set of test data that tests all possible conditions the program may encounter in the course of normal or even abnormal operating co
7. What is the output We need to solve for the change received from our transaction Second What are the inputs given The price of the textbook 79 95 The rate of the sales tax which is 5 Lastly we pay with a 100 bill Notice that before we can solve for the change received we must know a the amount of the sales tax and b the total amount of the sale including tax The storage areas for SalesTax and TotalCost are neither input or output They are listed under Processing P as Processing Items PI Next we must solve for how much sales tax will be charged This calculation is SalesTax 79 95 times 05 OR SalesTax PriceOfBook TaxRate Next we need to find the total cost of our purchase TotalCost 79 95 plus SalesTax OR TotalCost PriceOfBook SalesTax Last we need to calculate the change due from our 100 bill ChangeDue 100 TotalCost OR ChangeDue Payment TotalCost Our IPO chart should look like this I PI processing items O SalesTax TotalCost P PriceOfBook 79 95 SalesTax PriceOfBook TaxRate ChangeDue Tax Rate 05 TotalCost PriceOfBook SalesTax Payment 100 00 ChangeDue Payment TotalCost Our program will need more variables and three different calculations as we see above Note the change in the IPO Chart In the middle column there is a section marked PI Processing Items Processing Items are variables that need to be set up for interim calculations The
8. declared error message programname cpp author Jim Kelley date October 9 2009 This program demonstrates good style and comments include lt iostream gt using namespace std int main declare variables int numl1 int num2 int answer get data from users cout lt lt Enter a Number cin gt gt numl1 cout lt lt Enter a Number cin gt gt num2 processing here if numl lt num2 determine if num2 is larger than numl answer num2 numl1 if true subtract numl from num2 else if it is false answer numl num2 subtract num2 from numl1 display results cout lt lt The answer is lt lt answer lt lt endl return 0 end of main function Lesson 1 8 C TEMPLATE All C program exercises and examples will use the same basic template There are a group of statements common to all C programs we will be working with A skeleton C program is shown below This is the minimum code for all of your C programs Putting the comments up front all the lines that begin with is important to identifying your program I have also listed names for the files you create in all exercises naming conventions are extremely important to writing clear maintainable application programs Template for a C program programname cpp author date include lt iostream gt other include statements may be required using namespace std structs
9. places in the code to explain what a particular section of code has been designed to do Proper indentation means that you indent lines of code consistently to add readability to your code There is nothing harder to follow than a program that does not use indentation consistently Indentation helps you track where a section of code starts and ends This is a big help when you are trying to determine where a statement block starts and ends Consistent naming styles for variables and constants One style for constants is to make them in ALL UPPERCASE Then when you are looking at code you know that when you encounter a variable name in all uppercase it is a constant Naming your variables should be done in one of three ways pick one and stick with it 1 all lowercase characters 2 Camel case starting with a lowercase letter and using uppercase to separate words for example payrate would be written payRate 3 Using underscores in place of spaces to separate words like payrate would be written pay_rate Most C programmers stick with lowercase whenever possible Many programming languages are case sensitive and a programmer is always safe in using lowercase exclusively C variable names are case sensitive so when writing variable names you need to write them the same way in the code as you declared them initially Short meaningful names using one of the three styles we mentioned earlier are the best way to avoid the dreaded variable name not
10. problem That is What is the answer we are looking for When you discover what that is write the goal in the output O column Next we look at the word problem and decide what is the algorithm or the formula to arrive at the answer we are looking for Perhaps it is given as part of the problem or we may have to do some looking for an algorithm that will solve the problem Now that we know the algorithm we need to examine the word problem for input items Has sufficient data been given to us to solve the algorithm or the formula or the equation we found to solve the problem We need to make a list of all the inputs required note those values that have been supplied by the word problem and place them in the Input I column of the IPO chart Then back to the Processing column Now we need to write the pseudocode or flowchart the processes required to solve the problem These must be presented in the proper and logical order First we need to gather any information required from the user that was not supplied by the problem Next we need to plug all of the inputs into the algorithm Finally we need to display the output Example Let s examine the following word problem You want to do some home improvements so you take a one year loan at the rate of 5 85 and we have several estimates and need to calculate based on the amount you enter into the program How much interest will you pay Step 1 We need to discover the goal or the output
11. we calculate the change due by taking the amount of payment and subtracting the value calculated in the total cost step If these are done in any other order the result will be incorrect At the end of this process the contents of the chunk of memory assigned to each variable will look like Chunk called PriceOfBook 79 95 Chunk called TaxRate 0 05 Chunk called Payment 100 Chunk called SalesTax 4 Chunk called TotalCost 83 95 Chunk called ChangeDue 16 05 Now you should understand why your ability to solve word problems is critical to understanding how to develop a computer program You need to be able to solve the problem once manually before you can teach the computer to solve the problem by giving it the steps by which you solved the problem correctly Yes a program merely teaches or instructs the computer to do things in the order dictated by the programmer Another point often missed by beginning programmers is the remarkable similarity of these small programs Programs require that the programmer present the computer with directions in very specific order and syntax There must always be a line int mainQ This opens the programs main function This is how the computer knows where the instructions begin There must also be two lines at the very end return 0 End of Main Function This is how the computer knows when it is finished processing the program Everything between mus
12. SECTION I Using C Lesson 1 Overview of C Lesson 2 Problem Solving I Tools Lesson 3 Problem Solving II Word Problems Lesson 4 Problem Solving III Generating Test Data CHAPTER 1 Overview of C Objectives Identify various C compilers Describe Microsoft s Visual C List the steps to compile an executable file Explain the programming process Describe the statements common to most C programs Lesson 1 1 USING VISUAL C The Microsoft Visual Studio Programming Suite contains Visual C Microsoft s implementation of the C programming language The Microsoft C IDE Integrated Development Environment provides several tools to make programming in C much easier First there is the Editor which helps you format your program and color codes various segments of your program Next the ability to compile and debug your programs point and click Should there be errors in the way you have written your code statements syntax errors in your program the IDE will try to point you to the approximate line number where the error was detected Note the word approximate The first exercise will explain how to build your first C program Lesson 1 2 Why learn C The C language is one of the most widely used programming languages in the industry It is extremely flexible in its ability to solve problems from basic business applications to complex scientific applications This wide range of applications make
13. am to insure the change only affects the changed areas When changes are made to solve the problem new test data should be added to the series of test data
14. art calculate the Interest for each set of input data Where there is invalid data note that in the Interest column Lesson 4 3 Case Study We will now apply what we have learned about IPO charts and test data to an actual program We need to go though each step carefully and in order to develop a good plan for writing and testing our code Payroll We will create a basic payroll program that will ask the user for the employee number hours worked maximum 40 minimum 8 rate of pay maximum 25 00 minimum 6 35 and number of dependents maximum 7 It will calculate the gross pay and the federal tax for the employee and lastly calculate the net pay and display the following Employee Number Gross Pay Federal Tax and Net Pay Gross Pay is hours worked multiplied by rate of pay Federal tax is 15 of gross pay minus 1 000 for each dependent Net Pay is Gross Pay minus Federal Tax Let s create our IPO chart from the Payroll problem description First we are told that we need to calculate the Net Pay for the employee Second we are told to ask the user to enter employee number hours worked rate of pay and number of dependents We are given the calculation for Gross Pay hours worked times rate of pay Federal Tax 15 of Gross minus 1 000 times the number of dependents and Net Pay Gross Pay minus the Federal Tax Let s apply this information to an IPO chart T PI O P mploy number Get Employee Number Gross Pay hou
15. de and IPO charts as well as combination of these tools If done properly the coding testing and debugging of the program will be much quicker and the documentation of the final program will be easier and more accurate CHAPTER 3 Problem Solving II Objectives Define the output required in a word problem List inputs required by a word program Create an algorithm to solve the word problem List the steps needed to program a solution to the problem Explain the importance of using IPO charts Lesson 3 1 Word Problems In algebra we learned about solving for unknown variables like X Y Z In this equation we assign the value of Y Z to the variable X So if Y has the value 3 and Z has the value 2 the value of X will be 5 X 3 2 X 5 We can translate this into a C program as follows Algebra cpp This is a sample program int main Always required Open Bracket Always required Declare Variables A variable is an unknown value Unknown at the time of programming but may be assigned an initial value that may or may not be changed int Y 3 A variable named Y with a value of 3 int Z 2 A variable named Z with a value of 2 int X 0 A variable named X with a value of 0 Calculation X is assigned the value of Y plus Z X Y Z The variable X now contains the sum of Y plus Z 5 return 0 Always required Closing Bracket End of Main Function
16. for this word problem The last sentence is the key How much interest will you pay Interest is the number we have to come up with So we write Interest in the Output O column of the IPO Chart Step 2 Next we should decide on the formula for calculating the interest on a loan A little research will provide us with the formula Interest is equal to the Principal amount of the loan multiplied by the rate of interest multiplied by the term of the loan The actual formula is I P R T Step 3 Back to the word problem and see if we are given information about the Principal the Rate and the Term In the Input I column we need to put Principal user will enter Rate 0585 and Term 1 Step 4 Now we go back to the Processing P column and do the pseudocode for solving the problem 1 Get user input for the Principal amount rate and term of the loan 2 Plug the inputs into the algorithm I P R T 3 Display the output on the screen It is a good idea at this point to practice using the IPO chart You should practice several word problems using the IPO chart This will be helpful in analyzing word problems and turning them into C programs Lesson 2 6 IPO CHART All C program exercises and examples require an IPO chart prepared before beginning the code phase The IPO chart for the problem is shown below It is important to map out how to solve the problem before beginning to write the code An anonymous pr
17. hange One of the companies that use our payroll system have a new requirement We received the following request from their paymaster Payroll Change Request Acme Corp has decided to give all of our employees the opportunity to invest in a 401K program We will allow them to put between 0 and 10 of their Gross Pay into a 401k program We will deduct this amount pre tax before calculating the Federal Tax this reduces the amount of federal tax paid by the employee We also require the amount to be put in a 401K program be printed in the final report We need to go back and update our IPO chart appropriately to reflect the new changes Yes we should always keep our IPO chart as a form of documentation for our programs Then we should look at our test data and add the appropriate columns and rows to reflect the new changes Remember these changes will affect our calculated fields so we will have to re calculate each to insure proper test results We will also have to add rows to reflect testing possible scenarios from adding this new requirement I have shown the adjustments below Inputs Outputs Tests Emp Nbr Hrs Wkd Pay Rate Dependent 401K Gross Pay 401K Amt Federal Net Pay S Tax 12345 40 10 75 2 0 05 Normal 40 hr Pay 23456 40 9 0 0 05 Normal Pay No Dep 34567 40 10 8 0 05 Too many dep 45678 40 30 3 0 05 Invalid Pay Rate max 56789 45 10 0 0 05 Invalid Hours Hi 98765 7 10 0 0 05 In
18. it a popular language in education scientific engineering and the business world You can find the current ranking of C by going to the web site www tiobe com Lesson 1 3 Where is the C language used The C programming language is used to develop a wide range of applications It can be used by any local business to write a program to do their payroll or solve some other business problem requiring a custom built solution It may be used by a software developer to create a commerical package for a common application like a word processor or an accounts receivable package It is also used in Government Military aerospace and the scientific community Most engineering majors are required to take a course in C programming as it is widely used in engineering applications C is a compiled language so it is used where speed of processing is important Compiled means that the program contains all of the commands required by the program in the ones and zeros that the computer needs to do its processing Lesson 1 4 Different C Compilers Microsoft Visual Studio Visual C is a commercial product that is part of the Visual Studio NET suite It comes with an excellent editor compiler debugger and runtime environment Microsoft offers an Express version which is a free download from their web site of Express software devCpp is a free C compiler available from http www bloodshed net Bloodshed Software and you can download it to your
19. lve the problem This picture is called a flowchart It is a series of symbols connected by lines that depict the flow of the data to solve the problem While there are quite a few different symbols that can be used we will focus on a basic set of seven symbols that may be used to describe the flow of most programs e Terminal Process Decision Input Output Page connector Off Page Connector Flow Line SYMBOL FOR TERMINAL SYMBOL FOR PROCESS SYMBOL FOR DECISIONS SYMBOL FOR INPUT OUTPUT SYMBOL FOR PAGE CONNECTOR LJ SSE SYMBOL FOR FLOW LINE There are many more symbols but these are the important symbols for the purposes of this book SAMPLE FLOWCHART This flowchart represents a program that asks the user for two numbers Then compares those numbers and if they are equal the program prints Numbers are Equal If the numbers are not equal the program adds the two numbers and prints the sum For some programmers this type of visual representation is important to understand the flow of the code they will need to generate It can be a time consuming process to develop a neat flowchart that is accurate Often a flowchart is drawn in rough symbols on paper and then at the end when all has been considered drawn in a Word processor or with a flowcharting tool such as Microsoft s Visio or Dia a free tool similar to Visio Lesson 2 4 Pseudocode Pseudocode is another way to develop the logic of a program
20. n 0 End of Main Function Lesson 3 6 Summary Turning a word problem int an algorithm to solve the problem is often one of the most difficult tasks First you need to read the problem carefully and decide what information you need and what information you should throw out If you can t solve the problem on paper how will you write the code to solve the problem The more complex the problem the more complex the analysis and planning IPO charts seem to be one of the best tools for assisting beginning programmers in organizing their analysis of a word problem CHAPER 4 Problem Solving III Objectives e Explain the importance of a set of test data e Create test data for a program e Use test data for testing and problem solving Lesson 4 1 Test Data Preparing to test your program is often a task that is completely ignored However this may be one of the most important steps in software development Using a set of test data to test your program not only makes sure your program does what it was intended to do but also provides a means of conducting future tests after modifications have been made that insure you don t fix one problem and create a new problem A well crafted set of test data will test all of the possible values and conditions that the program is likely to encounter in the user environment The test data should not only be good data but also data that tests the error handling of the program You can count on the user e
21. nditions Implementation Once the program is free of errors and has been proven to produce accurate and consistent results it can be put into production Users trained to operate the program documentation written to explain how the program works and what it does and placed on the computers or servers that will host the application program Maintenance Even after a program is in use the users will find problems errors in calculation and usually new things the program should do that were never thought of before This is the maintenance phase and is ongoing throughout the life of the program Even such well known application programs like Windows Word Excel etc all have periodic updates done to fix problems found Lesson 1 7 Programming Style Exercising care in how you lay out your programs is an important step in making your programs easy to read and maintain As we introduce various elements of C we will demonstrate a particular style of programming When you develop a style of programming it should be used consistently Some of the elements of good programming are good use of comments proper indentation consistent naming styles for variables and constants and proper attention to case uppercase and lowercase letters Proper use of comments means that you put comment lines before your program that identify the name of the source file the author the date of the program and the purpose of the program You also place comments at key
22. ntain the program and possibly a developers manual to help the programming department understand how to write programs to interface with the product or to alter the product to fit company needs Then there should be a document that describes the various algorithms found within the program to insure the user knows how certain results were obtained from the input data Some companies will insist on training manuals and training materials to assist in bringing their workers up to speed on the program Developers may keep track of the weekly progress of the development and the problems encountered in the development cycle We will talk about a series of test data that will be used to validate the results of the program during testing The word documentation strikes fear in the heart of many programmers Programmers feel they are employed to write code not to write stories about their code Many resist writing the documentation required and even to the point where they would rather leave their job than write documentation Larger software companies have special documentation specialists to write the necessary documentation but often it is left to the person who wrote the code Lesson 2 8 Summary Programs are written to solve problems Taking a word problem developing an algorithm to solve the problem writing the code and finally testing and debugging the code is the mission Some of the tools used to develop the algorithm are Flowcharts Pseudoco
23. ntering a value that is out of range or the wrong data type It is important that your program handle these errors and does not blow up on the user Minimally test data should test boundaries one over a boundary one under a boundary illegal data on each field processed Test data also comes into play when you make modifications to an existing program You should be able to use the same test data to validate the changes you made did not affect the existing functions of the program When you find a problem with a program and fix the problem that test data should be added to your original test data The test data then becomes a document that grows as your application program changes Lesson 4 2 Building the Test Data First step is to create a chart to track each input calculation and output A spreadsheet is a great tool for keeping track of your test data and can be used to validate your calculations The alternative is a paper version and hand calculate all your outputs It might look something like this Principal Rate Term Months Interest The above form shows inputs and outputs for the Interest calcualtion problem The user is asked for the four inputs and the output is calculated To complete this form enter a variety of responses for the four inputs consider ranges and invalid data Once you have take care of the inputs using the algorithm for the calculation that we developed in our IPO ch
24. ogrammer once wrote Weeks of programming can save hours of planning Without a proper plan for your code it will take you many times longer to prepare a program than if you took the time to plan your process to solve the problem and then coded it IPO Chart for Interest Problem I Input P Processing O Output Principle 1 Get the user to input the principle amount of Interest Rate the loan Term of Loan 2 Get the user to input the interest rate 3 Get the user to input the term of the loan 4 Calculate the interest using the algorithm Interest Principle Rate Term 5 Display the output on the screen Lesson 2 7 Documentation In the world of programming the dreaded question is Where s the documentation Every programming project in the real world must be accompanied by some human readable content to explain various aspects of the program We create IPO charts which certainly are a part of documentation we insert copious comments into our code another form of documentation but we also need to provide a written narrative of the technical details of the program Various programming shops have different requirements for such written narratives and most expect this prior to acceptance of the final product If you are working for a company that writes commercial software you would be expected to provide a user manual to explain how to use the product an administrators manual to explain how to install and mai
25. one expresses a problem either verbally or written the programmer takes that information analyzes it develops the algorithm to solve the problem and turns it into a working program or system of interrelated programs Often developing the algorithm is the hardest part of solving the problem This is where the logic of programming becomes the brick wall in programming Too often beginning programmers do not take the time to analyze the problem and try to develop a working algorithm on the fly This may work for the simple problems at the beginning but makes the more advanced problems more difficult This is why we devote some time at the beginning of this book to the mechanics of solving problems and using problem solving tools Developing these skills at the beginning and following them throughout the course will make for a better learning experience Lesson 2 2 Tools Now we need to examine some of the tools used to analyze word problems and produce the proper analysis of the programming problem to assist the programmer in producing accurate code We will look at several of these tools flowcharting pseudocode IPO Charts and Documentation While some of these have the same function we wil talk about each of them and as your expertise develops you will learn which of these are best for you Lesson 2 3 Flowcharting Once we have learned to break out a problem it is often necessary to draw a picture of the process required to so
26. re your success in the remainder of this course Lesson 3 4 Why IPO CHARTS C program exercises and examples may require an IPO chart prepared before beginning the code phase Organizing your word problems into IPO charts may seem to be a complete waste of time but they do serve a vital service to the programmer This is your road map to creating an efficient well written program It is not evident in the simple problems we have looked at so far but in the not too distant future you will be writing more complex programs and user defined functions The lack of an IPO chart will make your programming and debugging of these programs far more difficult Lesson 3 5 Sample IPO Chart and Program PROBLEM Tom wants to borrow 1 000 for one year to purchase a new laptop His bank will give him the money at twelve percent interest for one year Tom wants to know how much interest he will pay on this loan IPO CHART E P O Principal 1000 Interest Rate 12 Interest Principal Term 1 times Rate times Term l Display Interest PROGRAM Interest cpp This is a sample program int main Declare Variables Variables known from data in the problem double principle 1000 00 double rate 0 12 double term 1 0 double interest 0 0 Interest Calculation interest principle rate term Display the result cout lt lt Interest on loan lt lt interest lt lt endl retur
27. rs worked Get hours worked Federal Tax rate of pay maximum 40 hours min 8 hours Net Pay number of dependents Get rate of pay maximum 25 00 minimum 6 35 Get number of dependents maximum 7 dependents Calculate Gross Pay hours worked times rate of pay Calculate Federal Tax Gross Pay times 15 minus number of dependents times 1 000 Calculate Net Pay Gross Pay minus Federal Tax Display Results Now we need to set up some test data We should first create values for each input and then calculate each calculated value When we run our program we should get exactly the same results Inputs Outputs Tests Emp Nbr Hrs Wkd Rate of Pay Dependents Gross Pay Federal Tax Net Pay 12345 40 10 75 2 Normal 40 hr pay 23456 40 9 0 Normal Pay No Dep 34567 40 10 8 Too many dependent 45678 40 30 3 Invalid Pay Rate 56789 45 10 0 Invalid Hours Hi 98765 7 10 0 Invalid Hours Lo 87654 40 25 7 All Max Values 76543 8 6 35 0 All Min Values 65432 40 6 2 Invalid Pay Rate Min Test data should be prepared prior to starting the code phase Preparing a table like we see above will help us understand the requirements of the programming phase Thinking of all the possibilities is an exercise that may help clarify the code required to solve the problem Lesson 4 4 Maintenance Once a program is in place we must realize the world changes and requirements c
28. t also be in a logical order For your simple beginning programs we can work with a template that will most often work for many of the programs you will be writing in this class Then as you learn the rules you can start to develop your own style of programming However be advised that in many programming shops you will be required to adhere to standards and styles of that shop and you may not be able to be as creative in style as perhaps you would like In our samples above we first declared all our variables This is important to do before the calculations because it tells the computer what the names of the variables are before the computer needs to use them We certainly want to name the memory areas and load them with data before we do any calculations The second step of our programs was to do the calculation or calculations required to solve the problem So our template for all the examples above were a simple two step template to declare variables and then do calculations Now you are ready to move on to more complex problems and examples To convert these problems into code it is often necessary to diagram the logic necessary for the computer to solve the problem There are many tools to accomplish this task but we have discussed three of these and learned to use them to organize our thoughts The three we have illustrated in this chapter are Flowcharting Pseudocode and IPO charts Practice using these tools and it will help to insu
29. valid Hours Lo 87654 40 25 7 0 1 All max values 76543 8 6 35 0 0 All min values 65432 40 6 2 0 05 Invalid Pay Rate Low 99943 8 6 35 0 0 No 401K 99932 40 6 2 0 1 Max 401K 99921 40 6 2 0 12 Exceed Max 401K Lesson 4 5 Importance of Test Data All C program exercises and examples will require test data to be prepared before beginning the code phase The importance of test data is often overlooked It helps us in a number of ways To organize our thoughts on the program requirements To think about input validation issues To validate our algorithms by making the programmer hand calculate outputs To insure changes do not adversely affect other calculations in the program So it is important to take the time to learn how to generate test data When you get a job in programming it will more than likely require that you generate a complete suite of test data for your program projects and demonstrate that your code successfully solves all of the test data situations both legal or illegal inputs Lesson 4 6 Summary Too often a program is not completely tested before it is released to the users Students get into the habit that when it seems to run successfully it is complete Building a series of test data is necessary to test ALL of the possibilities before releasing to the users they will find new problems The test data will also be used to re test the program when changes are made to the progr
30. y are neither input or output items They are needed for storing the interim results of calculations in the course of processing Hence the name Processing Items In our example above there are two processing items SalesTax and TotalCost As you can see looking at the three calculations SalesTax holds the amount of Sales tax calculated and TotalCost holds the cost of the book plus the sales tax Since the output is only the change due these values are not considered output but are necessary to store the results of these calculation so that the ChangeDue can be calculated Change cpp This is a sample program int main Declare Variables Variables known from data in the problem double PriceOfBook 79 95 double TaxRate 05 double Payment 100 00 Variables that will be calculated in the course of running the program double SalesTax 0 double TotalCost 0 double ChangeDue 0 Calculations Sales Tax Calculation SalesTax PriceOfBook TaxRate Total Cost Calculation TotalCost PriceOfBook SalesTax Change Due Calculation ChangeDue Payment TotalCost return 0 End of Main Function In the calculations section we can see how we must order the calculations properly so the result is correct First we must calculate the sales tax Next we calculate the total cost by using the price of the book plus the value we calculated for sales tax in the previous step Last
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