C++ Programming - OOPS Concepts - Discussion

Give an example program for each call by value, call by reference, call by pointer.

Eg : Call by value.

include <stdio.h>

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

int main ()
{
/* local variable definition */
int a = 100;
int b = 200;

printf("Before swap, value of a : %d\n", a );
printf("Before swap, value of b : %d\n", b );

/* calling a function to swap the values */
swap(a, b);

printf("After swap, value of a : %d\n", a );
printf("After swap, value of b : %d\n", b );

return 0;
}

Eg : call by reference & call by pointer one all the same.

#include <stdio.h>

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

int main ()
{
/* local variable definition */
int a = 100;
int b = 200;

printf("Before swap, value of a : %d\n", a );
printf("Before swap, value of b : %d\n", b );

/* calling a function to swap the values.
* &a indicates pointer to a ie. address of variable a and
* &b indicates pointer to b ie. address of variable b.
*/
swap(&a, &b);

printf("After swap, value of a : %d\n", a );
printf("After swap, value of b : %d\n", b );

return 0;
}

Please clarify me What is the difference between call by pointers and call by reference? Explain it with e.g.

In call reference we pass address so actual parameter value get change.

In call by value formal parameter get copied into actual parameter so actual parameter doesn't change as both have different memory.

Pointer also carries a address n reference also carries a address then what is the difference between call by pointer and call by reference.

In call by value we directly pass value and in call by reference we pass address of that value.

In call by reference: We passes the value in calling time.

And call by reference: We pass the address in calling time.

Call by reference:

void swap(int &x, int &y)
{
..
....

}

swap(a, b);
call by pointer:
void swap(int *x, int *y)
{
...
..

}

swap(&a, &b);

What is mean by call by value, call by Reference and its difference?

If it specifies means what is the answer?

Hi @Amol.

What was the out put of the example program?