6. Structure of C Program

Every C program is made of function and every function consist of instructions called statement.

Structure of C Program.

#include //stdio.h is the header file
main() // main function is the first function which is executed by a C program.

All C statements are written within main function.
{

// All C statements.

}

Functions

Every C program consists of one or more modules called functions. One of the functions must be called main( ).
The program will always begin by executing the main function, which may access other functions.

Any other function definitions must be defined separately, either ahead of or after main.

A function name is always followed by a pair of parenthesis, namely, ( ). And all function statements are enclosed within a pair of braces { }.

The program execution always starts with main function. When the closing brace of the main function is reached, program execution stops, and the control is handed back to the OS (Operating System).

Statements

Single C language instruction is called a statement. Statements are written according to the grammar of C language. Every C language statement must ends with semicolon(;).

In order to write a C program we should follow some basic rules which are described below:

a) Usually all statements in C are entered in small alphabets.

b) Blank spaces may be inserted between two words to improve the program readability. However no blank spaces are allowed within a variables, constants or key words.

c) It has no specific rules for the position at which statements is to be retained that's why it’s often called a free form language.

d) All C statements must end with a semicolon (; )