Programming for Problem Solving (3110003)

The parameters can be passed in two ways during function calling,

1. Call by value
2. Call by reference

Call by value

• In call by value, the values of actual parameters are copied to their corresponding formal parameters.
• So the original values of the variables of calling function remain unchanged.
• Even if a function tries to change the value of passed parameter, those changes will occur in formal parameter, not in actual parameter.

Example:

#include <stdio.h>
void swap(int, int); 
void main()
{
    int x, y;
    printf("Enter the value of X & Y:"); 
    scanf("%d%d", &x, &y);
    swap(x, y);
    printf(“\n Values inside the main function”); 
    printf(“\n x=%d, y=%d”, x, y);
}
void swap(int x,int y) {    
    int temp;
    temp=x;
    x=y;
    y=temp;
    printf(“\n Values inside the swap function”); 
    printf("\n x=%d y=%d", x, y); 
} 

Output:

Enter the value of X & Y: 3 5
Values inside the swap function
X=5 y=3

Call by Reference

• In call by reference, the address of the actual parameters is passed as an argument to the called function.
• So the original content of the calling function can be changed.
• Call by reference is used whenever we want to change the value of local variables through function.

Example:

#include <stdio.h>
void swap(int *, int *); 
void main()
{
    int x,y;
    printf("Enter the value of X & Y: 
    scanf("%d%d", &x, &y);
    swap(&x, &y);
    printf(“\n Value inside the main function”); 
    printf("\n x=%d y=%d", x, y);
}
void swap(int *x, int *y) {
    int temp;
    temp=*x;
    *x=*y;
    *y=temp;
    printf(“\n Value inside the swap function”); 
    printf("\n x=%d y=%d", x, y);
}

Output:

Enter the value of X & Y: 3 5
Value inside the swap function
X=5 y=3
Value inside the main function
X=5 y=3