Program

1. Program A computer program (also software, or just a program) is a sequence of instructions written in a sequence to perform a specified task with a computer.

2. Creating a C++ Program source code created using an IDE Object code Executable code: exe file An Introduction to Programming with C++, Fifth Edition

3. Processing a C++ Program (cont'd.) C++ Programming: From Problem Analysis to Program Design, Fifth Edition

4. The Problem Analysis–Coding–Execution Cycle (cont’d.) C++ Programming: From Problem Analysis to Program Design, Fifth Edition

5. Structure of C++ Program Header File Contains built-in-functions. These are also called pre-defined or already developed functions To include header files in our program Preprocessor Directives Angle or pointed brackets #include<iostream.h> #include<conio.h> void main( ) { cout<<“Welcome to Computer Scientists”; getch(); } h stands for header file 1 File name(standard input output ) Return type of main function. It is used to determines whether the program is executed successfully or not. Void means nothing Function Name Starting point of program execution 2 main function Parenthesis shows function. It is used to pass parameters/arguments Body Begin Program Body 3 Each statement must end with semicolon. A statement without semicolon generates syntax error. Body End Get character function. It get a character at runtime. But we use it to stay screen to see output Cout stands for console output.. It uses insertion operator (<<) print the output on the monitor/console. String or message to be displayed on monitor. It must be enclosed in double quotes(“ “)

6. Standard input and output streams cin Key Board >> … Standard input stream cout Monitor <<… <<… cerr Memory Standard output stream

7. Simple Steps to write and run a program in C++. • Go to this path C:\TC\BIN then double click on short to open C++ language. • Now save your program by choosing a meaningful program file name. e.g. welcome.cpp is a file name for a program that will display welcome message at runtime. • Now write your program as explained in the previous slide. (translation of algorithm to a c++ program).

8. 4. Press Alt+F9 key to compile program. If your program is error free then following screen will appear:

9. 5. Now press Ctrl+F9 key to run the program. Following screen shows the output of the program: Now press enter to go back to the source code of the program

10. Another Sample Program Program: #include<stdio h> void main() { int number; cout<<”Enter an integer: \n”); //message for user cin>>number; //get input cout<<”The number you entered is: “<<number; getch(); } Output:    Enter an integer:    25    The number you entered is: 25

11. Programming Style C++ is a free-format language, which means that: • Extra blanks (spaces) or tabs before or after identifiers/operators are ignored. • Blank lines are ignored by the compiler just like comments. • Code can be indented in any way. • There can be more than one statement on a single line. • A single statement can continue over several lines. In order to improve the readability of your program, use the following conventions: • Start the program with a header that tells what the program does. • Use meaningful variable names. • Document each variable declaration with a comment telling what the variable is used for. • Place each executable statement on a single line. • A segment of code is a sequence of executable statements that belong together. • Use blank lines to separate different segments of code. • Document each segment of code with a comment telling what the segment does.

12. Variable: Location in memory where value can be stored • An identifier is a name for a variable, constant, function, etc. Rules to Declare an Identifier (variable) • Alphabets from A to Z or a to z • The digits from 0 to 9 • Underscore(_) can be used • The first character of an identifier can not be a digit • The name of an identifier can not be a reserve word • No space allowed in the name of identifier Valid Name: A Student_Name _Fname Pi Inalid Name: $Sum //special ch. 6StName // 1st letter digit F name // no space allowed int // reserve word

13. Identifier (variable) Declaration Syntax Data-Type Space Variable-Name(Indentifier); e.g. intfrstNumber; char choice; float divide; long output; Identifier (variable) Initialization Syntax Data-Type Space Variable-Name(Indentifier) = Value; e.g. intfrstNumber=10; char choice=‘y’; float divide=0.0;

14. 45 45 72 45 72 first first second first second 117 sum Memory Concepts Variable Identifier • cin>> first; • Assume user entered 45 • cin>>second; • Assume user entered 72 • sum = first + second;

15. Assignment Operator (=) • = (assignment operator) • Assigns value to variable • Binary operator (two operands) • Example: sum = variable1 + variable2;

16. How many bytes I am eating?

17. Arithmetic • Rules of operator precedence • Operators in parentheses evaluated first • Nested/embedded parentheses • Operators in innermost pair first • Multiplication, division, modulus applied next • Operators applied from left to right • Addition, subtraction applied last • Operators applied from left to right

18. Comments Non - executable statements Comments are used for program documentation Two formats Single Line Comments Multi Lines Comments // This program is used to show the Welcome Message. /* This program is used to show the square of even numbers from 10 to 100. */

19. Tokens Tokens are individual words and punctuation marks in passage of text. In C++, program the smallest individual units are known as C Tokens. C++ has Six types of Tokens. The Tokens are shown in figure. C++ programs are written using these tokens and the syntax of the language.

21. C++ keywords • Each keyword has a predefined purpose in the language. • Do not use keywords as variable and constant names!! • Exmples: bool, break, case, char, const, continue, do, default, double, else, extern, false, float, for, if, int, long, namespace, return, short, static, struct, switch,typedef, true, unsigned, void, while etc etc..

22. Thank You New Computer Scientists

23. Memory Concepts • Variable names • Correspond to actual locations in computer's memory • Every variable has name, type, size and value • When new value placed into variable, overwrites previous value