.GRO File Extension

Bitmap image format sometimes referred to as a GROB (GRaphic Object Bitmap); used by Hewlett-Packard scientific calculators, such as the HP-48 and HP-49; used for storing graphs, charts, and other graphics created on the calculator.

GRO files may be viewed on a computer using a supporting HP calculator emulator, such as Emu48.

ASCII text file that defines audio in a MIDI representation; also contains "note tracks," which specify display data for the audio; can be imported (and subsequently converted to other audio formats) using Audacity's File → Import MIDI... option.