updated intro_lab instruction

README.md

@@ -50,7 +50,7 @@ All examples are available in both C and Fortran90.
 - OpenMP Intro lab: 
   - [Instructions](intro_lab/README.md)
   - Simple hello world program [in C](intro_lab/hello.c) and [in Fortran](intro_lab/hello.f90)
-  - Calculate pi [in C](intro_lab/pi.c) and [in Fortran](intro_lab/pi.f90)
+  - Calculate π [in C](intro_lab/pi.c) and [in Fortran](intro_lab/pi.f90)
   - Solutions will be made available later during the lab
 - OpenMP Advanced Lab: 
   - [Instructions](advanced_lab/README.md)

intro_lab/hello.c

@@ -5,4 +5,6 @@ int main ()
     int thread_id = 0;
 
     printf("Hello World from thread %d \n", thread_id);
+
+    return 0;
 }

intro_lab/pi.c

@@ -38,4 +38,6 @@ int main ()
     pi = step * sum;
     run_time = omp_get_wtime() - start_time;
     printf("\n pi with %ld steps is %lf in %lf seconds\n ",num_steps,pi,run_time);
+
+    return 0;
 }