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Call By Value

In call by value, original value is not modified.In call by value, value being passed to the function is locally stored by the function parameter in stack memory location. If you change the value of function parameter, it is changed for the current function only. It will not change the value of variable inside the caller method such as main().

Example

#include<stdio.h>
void change(int num)
 {
  printf("Before adding value inside function num=%d",num); 
  num=num+100;
  printf("After adding value inside function num=%d ", num);
}
int main()
 {
  int x=100;
  printf("Before function call x=%d", x);
  change(x);//passing value in function    
  printf("After function call x=%d", x); 
  return 0; 
}

Output

Before function call x=100
Before adding value inside function num=100
After adding value inside function num=200
After function call x=100

Call by reference in C

In call by reference, original value is modified because we pass reference (address).Here, address of the value is passed in the function, so actual and formal arguments shares the same address space. Hence, value changed inside the function, is reflected inside as well as outside the function.

Example

#include<stdio.h> 
void change(int *num) 
{
printf("Before adding value inside function num=%d,*num); 
(*num) += 100;
printf("After adding value inside function num=%d, *num);
 }
int main() {
int x=100; 
printf("Before function call x=%d, x);
change(&x);//passing reference infunction
printf("After function call x=%d ", x);
return 0;
}
  

Output

Before function call x=100
Before adding value inside function num=100
After adding value inside function num=200
After function call x=200 

Difference Between Call By Value and Call By Reference

Call By Value	Call By Reference
A copy of value is passed to the function	An address of value is passed to the function
Changes made inside the function is not reflected on other functions	Changes made inside the function is reflected outside the function also
Actual and formal arguments will be created in different memory location	Actual and formal arguments will be created

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