Question

What is the difference between passing an argument by value and passing it by reference? Provide for examples to support your answer.

Answer 1

Passing an argument by value means just a copy of the variable is passed as formal argument from the calling function to called function as actual argument.Whenever we change the value of variable in called function the actual value of variable in the calling function will not be effected.

Source code:

#include<stdio.h>
void called(int a)
{
   printf("the value of variable %d \n",a); // value of a before it's value has been changed
   a=10; // value of a has been changed
   printf("the value of variable %d\n",a);
}
int main()
{
   int n;
   printf("enter the value of variable\n");
   scanf("%d",&n);
   called(n); // the value of n is passed as formal parameter to called function;
   printf("the value of variable after the called function has been called %d",n);
   return 0;
}

Output:

C:\Users\SURAJNDesktop\prime.exe enter the value of variable 5 the value of variable 5 the value of variable 10 the value of variable after the called function has been called 5 Process exited after 2.819 seconds with return value e Press any key to continue

Passing an argument by reference  means just address  of the variable is passed as formal argument from the calling function to called function which is accept by a pointer as actual argument in called function.Whenever we change the value of variable in called function the actual value of variable in the calling function will also be changed as we accessing the actual variable by its address.

.Source code:

#include<stdio.h>
void called(int *a)
{
   printf("the value of variable %d \n",*a); // value of a before it's value has been changed
   *a=10; // value of a has been changed
   printf("the value of variable %d\n",*a);
}
int main()
{
   int n;
   printf("enter the value of variable\n");
   scanf("%d",&n);
   called(&n); // the value of n is passed as formal parameter to called function;
   printf("the value of variable after the called function has been called %d",n); // the value of n is changed after called function
   return 0;
}

Output:

CAUsers\SURAADesktop\prime.exe enter the value of variable the value of variable 5 the value of variable 10 the value of variable after the called function has been called 10 Process exited after 3.654 seconds with return value 0 Press any key to continue