Call by value and Call by reference in C Programming

Call by value and Call by reference in C are two ways to pass arguments in a function

Lets see above one by one

Call by value

Whenever we call a function and passes the value of variable to the called function is called call by value.

#include <stdio.h>
void swap(int x, int y);		/* function declaration */

 int main ()
 {
   int a = 10;
   int b = 20;
 
   printf("Value of 'a' before swap=  %d\n", a );
   printf("Value of 'b' before swap=  %d\n", b );
    
   swap(a, b);		// calling a function  swap & passes the value of variable
 
   printf("Value of 'a' after  swap=  %d\n", a );
   printf("Value of 'b' after  swap=  %d\n", b );
 
   return 0;
}

void swap(int x, int y) 		// function definition to swap the values 
{
   int temp;

   temp = x;
   x = y;   
   y = temp; 
  
   return;
}

#include <stdio.h>

void swap(int x, int y); /* function declaration */

int main ()

{

int a = 10;

int b = 20;

printf("Value of 'a' before swap= %d\n", a );

printf("Value of 'b' before swap= %d\n", b );

swap(a, b); // calling a function swap & passes the value of variable

printf("Value of 'a' after swap= %d\n", a );

printf("Value of 'b' after swap= %d\n", b );

return 0;

}

void swap(int x, int y) // function definition to swap the values

{

int temp;

temp = x;

x = y;

y = temp;

return;

}

OUTPUT

Value of 'a' before swap=  10
Value of 'b' before swap=  20
Value of 'a' after  swap=  10
Value of 'b' after  swap=  20

Value of 'a' before swap= 10

Value of 'b' before swap= 20

Value of 'a' after swap= 10

Value of 'b' after swap= 20

Call by reference

Whenever we call a function and passes the reference of variable to the called function is called call by reference.

In the call by reference, to pass the reference of the variable we use pointer.

#include <stdio.h>

void swap(int * x, int * y); /* function declaration */
int main() {
    int a = 10;
    int b = 20;

    printf("Value of 'a'  before swap= %d\n", a);
    printf("Value of 'b'  before swap= %d\n", b);

    swap( & a, & b); //call function swap and passes the reference of variable 

    printf("Value of 'a'  after  swap= %d\n", a);
    printf("Value of 'b'  after  swap= %d\n", b);

    return 0;
}

void swap(int * x, int * y) // function definition to swap the values 
{
    int temp;

    temp = * x;
    * x = * y;
    * y = temp;
    return;
}

#include <stdio.h>

void swap(int * x, int * y); /* function declaration */

int main() {

int a = 10;

int b = 20;

printf("Value of 'a' before swap= %d\n", a);

printf("Value of 'b' before swap= %d\n", b);

swap( & a, & b); //call function swap and passes the reference of variable

printf("Value of 'a' after swap= %d\n", a);

printf("Value of 'b' after swap= %d\n", b);

return 0;

}

void swap(int * x, int * y) // function definition to swap the values

{

int temp;

temp = * x;

* x = * y;

* y = temp;

return;

}

OUTPUT

Value of 'a' before swap=  10
Value of 'b' before swap=  20
Value of 'a' after  swap=  20
Value of 'b' after  swap=  10

Value of 'a' before swap= 10

Value of 'b' before swap= 20

Value of 'a' after swap= 20

Value of 'b' after swap= 10