Function is a group of statements that is used to perform any task. In another words we can say that a function is a self- contained block of programs that perform a coherent task.
Why to use function
Function is used to divide a large code into modules that helps us to debug and maintain the code.We can call any function multiple times.
There are various advantages of function:
- Code re-usability
- Easy to debug the program
- Code optimization.
Types of Functions
In C language, there are two types of functions that are given below:
- Library Function :
Library function is used to declare the c header file such as scanf(), printf() and many more.
- User-defined function
User define function is used to create own function and we can use it multiple times.
Defining a Function
We can define a function by using following syntax:
Syntax:
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return typefunction name( parameter list ) { body of the function } |
The function definition consists of a function header and a function body. There are following parts of a function.
- Return type: A function may return a value. If we don’t want to return a value then we have to use void.
- Function name: We can define the function name.
- Parameters:We can pass the valuein function at the time of calling.
- Function body:Function body is the collection of statements.
Let us consider an example:
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#include<stdio.h> void sum(); // declaring a function int a=5,b=10, c; void sum() // defining function { c=a*b; printf("Multiplication of (A*B) : %d\n", c); } int main() { sum(); // calling function return 0; } |
Call by value and call by Reference in C
In C language, there are two ways to pass the value of data to function.
- call by value.
- call by reference.
call by value:
We can’t change the original value at the time of passing value in the function but it can be changed for the current function only. It will not change the value of variable inside the caller method such as main().
Let us consider an example:
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#include<stdio.h> void abc(int id, int mob) { printf(" Passing value inside the abc function"); } int main() { int id=101, mob=90972762; abc(id, mob); // passing value to the function printf("\nValue of ID: %d",id); printf("\nValue of NAME: %d",mob); return 0; } |
call by reference:
We can change the original value while using call by reference through pass the reference (address).
Let us consider an example:
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#include <stdio.h> void fun(int *n) { printf("Adding value before inside the function=%d \n",*n); (*n) += 10; printf("Adding value after inside the function=%d \n", *n); } int main() { int x=10; printf("Before function call x=%d \n", x); fun(&x);//passing reference in function printf("After function call x=%d \n", x); return 0; } |
