Solution 1

C

#include <stdio.h>
#ifdef _OPENMP 
#include <omp.h> 
#endif

int main(int argc, char* argv[])
{
#ifdef _OPENMP
int iam;
#pragma omp parallel private(iam)
    { /* the parallel block starts here */
        iam=omp_get_thread_num();
#pragma omp critical
        printf("Hello from %d\n",iam);
    } /* the parallel block ends here */

#else
        printf("Hello, this is a serial program.\n");
#endif

    return 0;
}

 FORTRAN

 Program Hello_from_Threads
#ifdef _OPENMP
   use omp_lib
#endif
   implicit none

   integer :: iam
#ifdef _OPENMP

!$omp parallel private(iam)
   iam=omp_get_thread_num()

!$omp critical
   write(*,*) 'Hello from', iam
!$omp end critical

!$omp end parallel
#else
   write(*,*) 'Hello, this is a serial program'
#endif
end program Hello_from_Threads