Function In C

Modular programming:

Modular programming is programming concept. This concept allow us to divide a large solution into several small modules. Each module is devloped independently and act is a solution of small problem.

Need/Advantages of modular programming :

1. A module developed once and reuse several times in a program.
2. Due to readability, A problem will have less no of instruction.
3. A problem has less numbers of instruction has less number of errors.
4. program is easily maintainable .
5. program is easily extendable.

In C language to apply modular programming we use function or structures.

Function:-

A function is an individual unit of small set of instruction to solve a specific task. Function may be inbuilt or user Define.

User define function:- If a function not exist in language, it can be devloped by the user. The development of a function has 3 steps.

1. Function declaration ( Prototype )
2. Function calling
3. Function definition

Function declaration:-

Function declaration is a statement that declare a user define function, It describe the name of function, and return type of a function. The definition of a function must be placed out of other function in C language.

e.g.

Argument :-

Argument can be value or variable which given to a function during it’s calling.

Function calling :-

This is a statement where we call a function by using it’s name. During calling a function we have to pass all the Argument to the function.we can call a function several times.

Function Definition:-

Function Definition is the body of function (set of instruction). this body will execute when we call a function.The defection begin from header row. This header row contain return type,name of function and Argument variable of a function. A function definition may/may not return a value.

Defection of a function can not be placed within another function. Definition must be placed in globle scope of program.

A simple Function who calculate average of 4 integers :

#include<stdio.h>;
void main()
{
    int A,B,C;
    float res;
       // here we are declaring a function
    float average ( int , int , int , int );
    A = 12, B = 23 , C = 34;
       //now i am calling my function
    res = average(A, B, C, 45 );
       // see how to pass Arguments
    printf("Result is %.2f n",res);
       // here %.2f will allow 2 values printing after decimel
}
      // now i am defining my function
      // here you have to give names to argument 
      // here you can give names to argument what ever you want
   float average ( int num1 , int num2 , int num3 , int num4 )
     // here value of A copy in num1
     // here value of B copy in num2
     // here value of C copy in num3
     // here value of 45 copy in num4
{
     float z;
     z = num1 + num2 + num3 + num4 ;
     z = z/4;
     return z;
        // we use return keyword to return a value back to main 
       //function
}