What is pass by value in functions? | C Programming

Pass by Value: In this method, the value of each of the actual arguments in the calling function is copied into corresponding formal arguments of the called function. In pass by value, the changes made to formal arguments in the called function have no effect on the values of actual arguments in the calling function.
Example:
#include<stdio.h>
void swap(int x, int y) 
{
int t;
t = x;
x = y;
y = t;
}
 int main() 
{
int m = 10, n = 20;
printf("Before executing swap m=%d n=%d\n", m, n);
swap(m, n);
printf("After executing swap m=%d n=%d\n", m, n); return 0;
}
Output:
Before executing swap m=10 n=20
After executing swap m=10 n=20
Explanation:
In the main function, value of variables m, n are not changed though they are passed to function 'swap'. Swap function has a copy of m, n and hence it can not manipulate the actual value of arguments passed to it.