Inside a Classic: The TRS-80 Model 100

The Model 100's designers blessed the unit with ample expansion potential, especially for a compact computer of its size. You could connect an external floppy disk drive (the "Chipmunk" third-party drive was a popular option) or the Model 100's Disk/Video interface, which provided both disk-based storage and the ability to connect to a CRT monitor.

Unfortunately, most of its powerful expansion options had to squeeze through an inconveniently located 40-pin expansion bus on the bottom surface of the unit, seen here. Immediately below that, you'll notice a free slot for a user-provided software ROM chip, which proved essential in extending the 100's usefulness. It allowed users to add software for spreadsheets, bar code scanners and the like.