A relatively simple MPI code is shown here. You will notice how the code mirrors the general structure of MPI programs:

 
call-procs.c: 
#include <math.h> // math library 
#include <stdio.h>// Standard Input/Output library 
 
int main(int argc, char** argv) 
{ 
  /* MPI Variables */ 
  int num_processes; 
  int curr_rank; 
  int proc_name_len; 
  char proc_name[MPI_MAX_PROCESSOR_NAME]; 
 
  /* Initialize MPI */ 
  MPI_Init (&argc, &argv); 
 
  /* acquire number of processes */ 
  MPI_Comm_size(MPI_COMM_WORLD, &num_processes); 
 
  /* acquire rank of the current process */ 
  MPI_Comm_rank(MPI_COMM_WORLD, &curr_rank); 
...