# mopac > MOPAC (Molecular Orbital PACkage) is a semiempirical quantum chemistry program based on Dewar and Thiel's NDDO approximation. > More information: . - Perform calculations according to an input file (`.mop`, `.dat`, and `.arc`): `mopac {{path/to/input_file}}` - Minimal working example with HF that writes to the current directory and streams the output file: `touch test.out; echo "PM7\n#comment\n\nH 0.95506 0.05781 -0.03133\nF 1.89426 0.05781 -0.03133" > test.mop; mopac test.mop & tail -f test.out`