1. Computer Programming TCP1224 Chapter 3 Completing the Problem-Solving Process and Getting Started with C++

2. Week 2 – What we talked about Analysis of a problem Input-Process-Output (IPO) Chart Algorithm Pseudocode and Flowchart 2

3. Comments about tutorial I am glad that many of you tried it, but many seem to be unsure of what you were doing. From my limited observation; ▫Many are probably thinking “what does this have to do with programming?” ▫Some have already sounded out that programming may be difficult! (utter nonsense, it is very easy). What is programming? ▫Syntax that is hard to remember? ▫The need to learn another communication language? ▫It’s that sequence, repetition and selection thing-a-mie-bob? 3

4. UN-official view of programming It is a set of simple to follow instructions for a dumb piece of machinery that has to be spelt out step by step in simple to understand language. ▫Most of us explain an issue or answer questions for people who have some intelligence and will understand our answers. E.g.,  Do you drink?  Meaning “do you drink any alcoholic beverage”?  Where were you?  Usually meaning, “I was looking for you all over and could not find you, where were you at noon when I came to you room?” 4

5. UN-official view of programming Now, imagine that you need to explain to someone who has no sign of intelligence. ▫You will need to speak to that person sloooowwwwlyyyyyy … or actually, you need to speak to that person, word by word. ▫So, same as how you would tell the computer, as in programming. You need to tell step by step … it is really dumb! ▫So, back to the lecture … a computer can only execute instructions in sequence, is able to repeat (repetition) and you can tell it how to decide (selection). 5

6. So, what’s this IPO chart for? For you to tell the “intelligent-less” machine, what it can work with (the input) to produce the results (output). The “processing” component is the step by step instructions for the computer. ▫A computer has no intelligence, so even a simple thing like obtaining the input has to be told. E.g. “Enter the loan period”. It is better to maybe even say, “get input from keyboard for the loan period in months”. ▫You will need to specify these steps. ▫In your mathematics classes, you have often been told to answer showing the steps you used to derive the results. 6

7. Math example A very popular math solving step … Let x = y x ( – y + y ) = y x – y + y / ( x – y ) = y / ( x – y ) 1 + y / ( x – y ) = y / ( x – y ) 1 = ( y / ( x – y ) ) - ( y / ( x – y ) ) 1 = 0 7

8. Algorithm In general, most of you need to be more detailed in your algorithm. Clearly state where does the values used originate from and what each notation mean. Proof read it by making yourself “intelligent-less” and determine if what you wrote can produce the output required. 8

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10. This week’s objectives? Code an algorithm into a program (How to) Desk-check a program (as oppose to Desk-check the algorithm) Evaluate and modify a program Understand the components of a C++ program Create a C++ program 10

11. Concept Lesson More on the Problem-Solving Process Coding the Algorithm into a Program Desk-Checking the Program Evaluating and Modifying the Program Creating a C++ Program 11

12. More on the Problem-Solving Process 12

13. Coding the Algorithm into a Program 13

14. Assigning Names, Data Types, and Initial Values to the IPO Items To code algorithm (i.e. to be able to transform from the algorithm to a program), first assign a name to each input, processing, and output item in IPO chart. By convention; ▫Names can contain only letters, numbers, and _ ▫Cannot contain punctuation characters or spaces ▫Examples:  raise  newPay ▫Each input/processing/output item must have a data type ▫You may initialize each item 14 usually in lowercase letters use camel case if name contains multiple words

15. Assigning Names, Data Types, and Initial Values to the IPO Items Camel case ▫The words are written without any spaces in between them, and the first letter of the 2 nd and following words are capitalized. ▫This creates humps on the words and hence are known as camel case. ▫E.g. thisLectureIsBoring Data type ▫A computer stores information in bits and bytes and have limited variations. In each and every name given, the computer has to be told how to store them and how to use them. ▫E.g. if it is a real number, the C++ language calls it a float or double. Why the difference? Initialize ▫Each time you create a new “variable”, it is just a name. More often than not, you need to put something in there. 15

16. Assigning Names, Data Types, and Initial Values to the IPO Items 16 double is a keyword this is a statement all C++ statements must end with a semicolon

17. Translating the Algorithm into Code 17 cout : standard output stream cin : standard input stream << : insertion operator >> : extraction operator stream: sequence of characters, to perform standard I/O operations a stream manipulator

18. Review: The core C++ code 18

19. Desk-Checking the Program 19

20. Desk-Checking the Program (continued) 20

21. Desk-Checking the Program (continued) 21

22. Evaluating and Modifying the Program Testing is running the program, with sample data ▫Results should agree with desk-check ones! Debugging is locating/removing errors in program ▫Program errors are called bugs 22

23. Evaluating and Modifying the Program A syntax error occurs if an instruction violates the programming language’s syntax (set of rules) ▫E.g., cout < "Hello"; A logic error occurs if an instruction does not give the expected results ▫E.g., average = number1 + number2 / 2; 23

24. Creating a C++ Program 24 source file: Ch3Lab2.cpp object file: Ch3Lab2.obj executable file: Ch3Lab2.exe created using an IDE or a general-purpose editor

25. An Introduction to Programming with C++, Fifth Edition 25

26. Summary Fourth step in the problem-solving process is to code the algorithm into a program In C++, you perform standard I/O operations using streams (sequences of characters) ▫ cout and cin ▫Insertion operator (<<) sends data to output stream ▫Extraction operator (>>) gets data from input stream After coding the algorithm, you desk-check program Final step in the problem-solving process is to evaluate and modify (if necessary) the program 26

27. Summary (continued) Some programs have errors, called bugs ▫Syntax error occurs when an instruction violates one of the rules of the programming language’s syntax ▫Logic error occurs when you enter an instruction that does not give you the expected results ▫You debug to locate and remove errors To create and execute a C++ program, you need to have a text editor and a C++ compiler ▫Compiler translates source code into object code ▫Linker produces executable file 27

28. Summary (continued) Comments are internal documentation of programs C++ programs typically include at least one directive using statements tell compiler where it can find the definition of certain keywords A function is a block of code that performs a task ▫ main() is where the execution of program begins The first line in a function is called the header ▫After the header comes the body, enclosed in braces 28

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