Write a C Program to perform Call By Value and Call By Reference methods

Below is the source code for C Program to perform Call By Value method which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/*  Call by value*/

#include<stdio.h>
void value(int x, int y);
int main( )
{
        int a=5, b=8;
        printf("Before calling the function, a = %d and b = %d\n", a, b);
        value(a, b);
        printf("After calling the function, a = %d and b = %d\n", a, b);

    return 0;
}
void value(int x, int y)
{
        x++;
        y++;
        printf("Inside function x = %d , y = %d\n",x,y);
}

OUTPUT : :

Before calling the function, a = 5 and b = 8
Inside function x = 6 , y = 9
After calling the function, a = 5 and b = 8

Call by Reference

• If data is passed by reference, a pointer to the data is copied instead of the actual variable as is done in a call by value. Because a pointer is copied, if the value at that pointers address is changed in the function, the value is also changed in main().

• In call by reference, original value is modified because we pass reference (address).

• Here, address of the value is passed in the function, so actual and formal arguments shares the same address space.Hence, value changed inside the function, is reflected inside as well as outside the function.

Below is the source code for C Program to perform Call By Reference method which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/* Call by reference*/

#include<stdio.h>
void ref(int *p, int *q);
int main()
{
        int a = 5;
        int b = 8;
        printf("Before calling the function, a = %d and b = %d\n", a, b);
        ref(&a, &b);
        printf("After calling the function, a = %d and b = %d\n", a, b);
        
        return 0;
}
void ref(int *p, int *q)
{
        (*p)++;
        (*q)++;
        printf("Inside function *p = %d, *q = %d\n", *p, *q);
}

OUTPUT : :

Before calling the function, a = 5 and b = 8
Inside function *p = 6, *q = 9
After calling the function, a = 6 and b = 9

Conclusion of Call By Value and Call By Reference :