The TRS‑80 Model 4, introduced on April 26, 1983, was the continuation of the TRS‑80 computer line that began with the Model I in 1977. Features The Model 4 strongly resembled the Model III that it replaced. The most noticeable difference was the color: white instead of the battleship grey that dated back to the Model I. Some of the new features included: a 4Mhz clock speed (double that of the Model III) a full 64K of RAM plus support for another 64K of extended memory an 80 by 24 screen with reverse video an expanded keyboard with function keys TRSDOS 6 operating system with Microsoft BASIC CP/M compatibility This one has an extra Floppy drive instead of the cover plate. The computer is starting up but asks for a floppy disk. The original boot disk is missing. This is the most extensive version ( Model no 260-1069) Serial number: 004306