Am having some trouble compiling a simple fortran program on my M1 MacBook Air. I am using the latest MacOS, Monterey 12.3.1, and the latest version of Xcode. I installed Homebrew and gcc to update my old version of gfortran. The fortran program on my desktop will compile when I use the command gfortran -c skippy.f, producing the executable file skippy.o on my desktop. But I can’t get the executable file to run. I am an amateur and am really not that familiar with the unix commands, etc. Can someone give me some advice on this? Thanks.

-Dave

~/Desktop 519 $ gfortran -o skippy.f
gfortran: fatal error: no input files; unwilling to write output files
compilation terminated.
~/Desktop 520 $ gfortran -c skippy.f
~/Desktop 521 $ ./skippy.o
-bash: ./skippy.o: Permission denied
~/Desktop 522 $ gfortran skippy.f
ld: library not found for -lSystem
collect2: error: ld returned 1 exit status
~/Desktop 523 $ g77 skippy.f
-bash: g77: command not found
~/Desktop 524 $