Running a C program on Mac OS X
created with GCC 5.2.0
gcc exio.c -o exio.app

Download exio.app
Note: I used the .app extension, but that is not necessary.exio

Open the terminal app in Applications/Utilities

Run it 
Go to where you saved it (e.g. Downoloads) in the finder with cd (change directory)
  cd Downloads
Make it executable "chmod +x exio.app"
Run it
  ./exio.app

Links: