This is an all-in-one desktop computer manufactured during the 1980s which features a built-in monitor, keyboard, and disk drives.

The 1987 Radio Shack catalog listed this system at $1199 USD. It included the TRS-80 version of Tandy DeskMate, a software package that has a word processor, spreadsheet, and other useful programs. It has seventy-one keys.

The '89 catalog still listed it at the same price. It called the 4D a "favorite of businesses and educators". It's possible to add a hard drive to this computer; the catalog listed a hard disk controller (#26-1138) for $449.

According to the "Secret Guide to Computers", the Tandy TRS-80 4D has 5.25" floppy drives and uses 360k disks with 18 sectors, 40 tracks, and two sides. The same book indicates that this computer uses the TRSDOS operating system.

Differences between the 4D and the original model four are few. The above-mentioned (higher) floppy disk capacity is one way this model was different from the Tandy TRS-80 Model 4 and the 4P. The 4P did not appear in the above-mentioned 1987 or 1989 catalogs.

A technical reference manual was published for models 4/4P/4D. It was Radio Shack catalog number 26-2119.