updated intro_lab instruction

intro_lab/README.md

@@ -22,24 +22,20 @@ To compile your C OpenMP code using the default Cray compilers:
 cc -O2 -openmp -lm name_source.c -o name_exec
 ```
 
-In Fortran, you need to use the Intel compiler. On Beskow, you first need to
-switch first from Cray to Intel compiler with:
+Alternatively, compile your C OpenMP code using GNU compilers:
 
 ```
-module swap PrgEnv-cray PrgEnv-intel
+module swap PrgEnv-cray PrgEnv-gnu
+cc -O2 -fopenmp -lm name_source.c -o name_exec
 ```
 
-and then compile with:
+In Fortran, it is recommended to use the Intel compiler
 
 ```
+module swap PrgEnv-cray PrgEnv-intel
 ftn -fpp -O2 -openmp -lm name_source.f90 -o name_exec
 ```
 
-<!---
-**Very Important**: Do not copy and paste from this document to your terminal
-since the - symbol will create problems when compiling.
--->
-
 To run your code on Beskow, you will need to have an interactive allocation:
 
 ```