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. 1

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

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

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

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

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

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. 2. 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. 3. Now write your program as explained in the previous slide. (translation of algorithm to a c++ program). 7

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

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 9

Another Sample Program Program: #include 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 10

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. 11

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 Rules to Declare an Identifier (variable) Valid Name: A Student_Name _Fname Pi Inalid Name: $Sum //special ch. 6StName // 1 st letter digit F name // no space allowed int // reserve word 12 Variable: Location in memory where value can be stored An identifier is a name for a variable, constant, function, etc.

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

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

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

How many bytes I am eating? integer data short2 bytes int2 bytes(16 bit system) 4 bytes (32 bit system) long4 bytes Floating point data float4 bytes double8 bytes long double10 bytes Characterchar 1 byte Booleanbool 1 byte 16

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 17

Comments Non - executable statements Comments are used for program documentation Two formats Single Line CommentsMulti 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. */ 18

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. 19

20

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.. 21

22 Thank You New Computer Scientists

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 23