Types of function

In C Language, when function is called with arguments, you can pass the values using 2 ways: call by value and call by reference.

1. Call by value When a function is called and value of a variable is passed via argument it is known as call-by-value. In this case, any changes made inside the function have no effect on another functions.
2. Call by Reference When a function is called and reference (address) of a variable is passed via argument it is known as call-by-reference. In this case, changes will reflect in another functions.

#include<stdio.h>
#include<conio.h>

void fun(int); //function declaration
void main()
{
    int a=10;
    clrscr();
    fun(a);  //function call
    printf("\nValue of A outside function is = %d",a);
    getch();
}
void fun(int a) //function definition
{
    a=20;
    printf("\nValue of A inside function is %d",a);
}

#include<stdio.h>
#include<conio.h>

void fun(int &a); //function declaration
void main()
{
    int a=10;
    clrscr();
    fun(a);  //function call
    printf("\nValue of A outside function is = %d",a);
    getch();
}
void fun(int &a) //function definition
{
    a=20;
    printf("\nValue of A inside function is %d",a);
}

Example 3: Program to return multiple values by using call by reference.

#include<stdio.h>
#include<conio.h>

void AreaCircum(float, float &ar, float &cir);
void main()
{
    float radius, area=0, circum=0;
    clrscr();
	printf("Enter Radius: ");
    AreaCircum(radius, area, circum);
    printf("\nArea of Circle = %f",area);
    printf("\nCircumference of Circle = %f",circum);
    getch();
}
void AreaCircum(float r, float &ar, float &cir)
{
    ar=3.14*r*r;
    cir=2*3.14*r;
}

Exercise Questions:

1. WAP to Swap 2 Numbers using Call by Reference