Saturday, 8 March 2014

An illustration of Calling a Function in C

When you call any function : there are two way to pass Value to it .  Today we discuss benefits of these two approaches .

CALL BY Value :   

In This Cause we just pass a copy of actual value and any change to this data in called function NOT change actual Value of The data in Caller function (which passes argument ).
Take an example : Swapping two number   without using third variable .

  1. #include <stdio.h>
  2. void swap (int, int);
  3. int main ()
  4. {
  5.         int a,b;
  6.         printf("An Illustration of Call by value\n");
  7.         printf("\nEnter the first number :\n");
  8.         scanf("%d",&a);
  9.         printf("\nEnter the second number :\n");
  10.         scanf("%d",&b);
  12.     printf("\nCall by Value..  \n")
  13.                 swap(a,b); //calling function and print new value in that func;
  15.     printf("\nIn main function ..");
  16.         printf("\nthe first number is %d \n",a);  //printing value of a & b in main 
  17.         printf("\nthe second number is %d\n",b);
  18.         return 0;
  19. }
  20. void swap (int x, int y)
  21. {
  22.         x=x+y; //swapping without using third variable 
  23.         y=x-y;
  24.         x=x-y;
  25.         printf("\nNow the first number is : %d \n",x);
  26.         printf("\nNow the second number is : %d \n",y);
  27. }

In this above example you can see first we call the function swap by method of call by value than than print its new values in function swap . But changing value in swap function does not alter value in main function .

CALL BY Reference  :

In this method we pass address of variable to be passed .  since now change made in values at this address obviously alter the value in caller function (here main )

Let us discuss above case : when we call by reference ....

  1. #include <stdio.h>
  2. void swap (int *, int *);
  3. int main ()
  4. {
  5.         int a,b;
  6.         printf("An Illustration of Call by reference\n");
  7.         printf("\nEnter the first number :\n");
  8.         scanf("%d",&a);
  9.         printf("\nEnter the second number :\n");
  10.         scanf("%d",&b);
  11.         swap (&a,&b);
  12.         printf("\nCall by Reference.. \n");
  13.         printf("\nNow the first number is %d \n",a);
  14.         printf("\nNow the second number is %d \n",b);
  15.         return 0;
  16. }
  17. void swap (int *x, int *y) //receive address in pointer 
  18. {
  19.         *x=*x+*y; //swapping without using third variable 
  20.         *y=*x-*y;
  21.         *x=*x-*y;
  22.         printf("\nNow the first number is : %d \n",*x);
  23.         printf("\nNow the second number is : %d \n",*y);
  24. }

you can see output ... . actual value in main function also changed .

Output for above two program is :

Thanks : Have a Nice Day


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