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Call by Value
The call by value method of passing arguments to a function copies the actual value of an
argument into the formal parameter of the function. In this case, changes made to the parameter
inside the function have no effect on the argument.
By default, C programming uses call by value to pass arguments. In general, it means the
code within a function cannot alter the arguments used to call the function. Consider the function
swap() definition as follows.
Now, let us call the function swap() by passing actual values as in the following example:

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

{
int temp;

temp = x; /* save the value of x */

x = y; /* put y into x */
y = temp; /* put temp into y */

return;

}

#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 );

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