int nthreads, tid;
#pragma omp parallel private(tid)
/* Obtain and print thread id */
tid = omp_get_thread_num();
printf("Hello World from thread = %d\\n", tid);
/* Only master thread does this */
if (tid == 0)
nthreads = omp_get_num_threads();
printf("Number of threads = %d\\n", nthreads);
} /* All threads join master thread and terminate */
Make sure that you use the proper compiler option to compile your code with OpenMP pragmas: "-openmp" on Linux and "/Qopenmp" on Windows.
You might not notice any problems while compiling your code because the compiler just emits the warning about unrecognized pragma but not the error.