How to calculate the time required to execute a particular program

The following program shows how to calculate the time taken to execute a program. The program is implemented using c. Here <time.h> header file is included.

Output : 

Code :

#include<stdio.h>
#include<time.h>
int main()
{
 int i;
 clock_t begin,end;
 begin=clock();
 for(i=0;i<5;i++)
 {
  printf("Hello world\n");
 }
 end=clock();
 
 printf("Time taken : %lf\n",(double)(end-begin)/CLOCKS_PER_SEC);
 return 0;
}