Skip to main content

Call by value vs call by reference

Difference between call by value and call by reference
There are two types of parameter passing schemes.
     1. Call by value
     2. Call by reference

Call by Value:
     A copy of actual arguments are passed to the formal arguments.  So, any modification to formal arguments won't affect the original value of actual arguments.

Example C program to illustrate call by value:
 
  #include <stdio.h>
  /* swaps given two number */
  void swap(int a, int b) {
        int tmp;
        tmp = a;
        a = b;
        b = tmp;
        printf("Inside swap() -> a = %d\tb = %d\n", a, b);
        return;
  }

  int main() {
        int a, b;
        printf("Enter two integers: ");
        scanf("%d%d", &a, &b);
        swap(a, b); // pass by value
        printf("Inside main() -> a = %d\tb = %d\n", a, b);
        return 0;
  }

  Output:
  jp@jp-VirtualBox:~/$ ./a.out
  Enter two integers: 10 20
  Inside swap() -> a = 20 b = 10
  Inside main() -> a = 10 b = 20



Call by Reference:
Here, the address of variables are passed from the actual argument to the formal argument.  So, the called function acts on addresses rather than values.  Here, the formal arguments have the pointer to the actual arguments. So, any change made to formal arguments reflect on actual arguments.

Example C program to illustrate call by reference
 
  #include <stdio.h>
  /* swaps given two number */
  void swap(int *a, int *b) {
        int tmp;
        tmp = *a;
        *a = *b;
        *b = tmp;
        printf("Inside swap() -> *a = %d\t*b = %d\n", *a, *b);
        return;
  }

  int main() {
        int a, b;
        printf("Enter two integers: ");
        scanf("%d%d", &a, &b);
        /* address of variable is passed to swap() */
        swap(&a, &b);  // pass by reference
        printf("Inside main() ->  a = %d\t b = %d\n", a, b);
        return 0;
  }

  Output:
  jp@jp-VirtualBox:~/$ ./a.out
  Enter two integers: 10 20
  Inside swap() -> *a = 20 *b = 10
  Inside main() ->  a = 20 b = 10



Labels:

Comments

Post a Comment

Popular posts from this blog

Array of pointer to structure

Array of pointer to structure is nothing but an array whose elements are pointers to structure How to declare array of pointer to structure? Below is an example declaration for array of pointer to structure. struct student *arr[10]; Here, arr is an array 10 of pointer to structure student. Dynamic memory allocation: Below is the procedure to perform dynamic memory allocation for the structure pointers in an array. struct student { int age; char name[32]; }; fun() { int i = 0; struct student *arr[10]; for (i = 0; i < 10; i++) { /* dynamic memory allocation for 5 structure objects */ arr[i] = (struct student *)malloc(sizeof(struct student) * 5); } } Write a c program to pass an array of structure pointers to another function   #include <stdio.h>   #include <stdlib.h>   #include <string.h>   struct student {         int age, rollno;         char name[32];   };   /* printing details of stude...
Post a Comment
Read more

Nested function in C

What is nested function? If a function is defined inside another function, then it is called as nested function.  Nested function example in C: Consider the following example, int add(int a, int b) {        void print(int res) {          printf("Result is %d, res);       }       print(a+b);       return 0; } Here, print() is a nested function.  Because, it is defined inside another function named add() . Example C program using nested functions: #include <stdio.h> void add(int a, int b) { void print(int res) { // nested function printf("Result is %d\n", res); return; } print(a + b); // passing sum of a and b as parameter return; } int main() { add(10, 20); return 0; }   Output:   jp@jp-VirtualBox:~/$ ./a.out   Result is 30 Previous Next
Post a Comment
Read more

Difference between asterisk and ampersand operators in c

Address Operator (& - Ampersand): Returns address of the given variable.  Consider the following example, int *ptr, var = 10; ptr = &var; ptr = &var sets the address of the variable var to pointer ptr.  & is also called as reference operator. Let us try to understand the purpose of reference operator using the following example program.   #include <stdio.h>   int main() {         int var = 10, *ptr;         /* assigning address of variable var to pointer ptr */         ptr = &var;         /* printing the address of the variable var */         printf("Address of var is 0x%x\n", &var);         /* printing the value of pointer ptr */         printf("Value of ptr is 0x%x\n", ptr);         return 0;   }   Output:   jp@jp-VirtualBox:~/$ ./a.out   Address of var is 0x...
Post a Comment
Read more