Sunday, 1 April 2012

Structure Of a C Program

A typical c program has the following structure:
  1. Pre Processor Directives
  2. Declaration Of Global Variables
  3. Function Prototype
  4. Main Function
  5. User Defined Function definition.
//pre processor directive
//declaration of global variables
int k=0;
//function prototype void add(int,int); //main function void main() { int a=10; add(a,k); } //User defined Function definition void add(int value1,int value2) { printf("sum:%d",value1+value2); }

Pre Processor Directives:

These are the directives to the compiler, they are followed while compiling the code.

1.#include<****.h>:directive to include the header file during 

2.#define PI 3.1419  directive defining the value of constant PI,
wherever PI is used it will be replaced by 3.1419

Function Prototype:

A function prototype is nothing but signature of function.(for more info read article on functions) 
int add(int,int);
It informs the compiler about the existence of a function add in the program.(whose body may be defined after the main function.)

Declaration Of Global Variables:

Global variables are those variables which can be used/ whose scope is throughout the program, ie these variables are common to main function and user defined functions.These variables have to be declared before the main function.

Main Function:

Every C program should have a main function, the execution of a program starts from main function.
However the we can call all other functions from a main function.(Read article on functions for more info on calling a function.).

User Defined Function Definition:

user defined function definition contains the logic for user defined functions.
void add(int var1,int var2)
this function adds the two variables passed and prints the results on the computer screen.
similarly we can define custom functions to perform tasks desired by us.

No comments:

Post a Comment