IBM System/23 Datamaster

The System/23 Datamaster (Model 5322 desktop model and Model 5324 floor model ) is an 8-bit microcomputer developed by IBM. Released in July 1981, the Datamaster was the least expensive IBM computer until the far less expensive and far more popular IBM PC was announced in the following month.

Description
The Datamaster is an all-in-one computer with text-mode CRT display, keyboard, processor, memory, and two 8-inch floppy disk drives in one cabinet. The processor is an 8-bit Intel 8085 running at 4.77 MHz, with bank switching to manage 128 KB of memory. Available RAM was 32 KB (expandable to 128 KB ), and the machine had four internal expansion slots. It could display 80 × 24 characters of text (each character with 10 × 14 pixels) with 256 possible characters, similar to the IBM PC's Code page 437, on a built-in 12" green phosphor CRT.

The intention of the Datamaster was to provide a computer that could be installed and operated without specialists. A BASIC interpreter was built-in to the system. IBM decided to merge the Datamaster's BASIC implementation with System/34 BASIC, which reportedly delayed the Datamaster by almost a year. When introduced, a single-screen Datamaster sold for around US$9000 1981. A second keyboard and screen could be attached in an extended configuration.

Influence on later IBM systems
The familiarity the design group gained on the Datamaster project encouraged selection of an Intel CPU for the IBM PC. The delay caused by the decision to reuse System/34 BASIC in the Datamaster was one of the factors in IBM's selection of Microsoft BASIC for the PC (the other being the popularity of Microsoft BASIC on home computers at the time).

A number of hardware components from the Datamaster were reused in the later IBM PC. The PC's expansion bus, later known as the ISA bus, was based on the Datamaster's I/O bus. The Datamaster's Model F keyboard with its 5251-style key arrangement was also reused in the PC, albeit with a serial interface (instead of the parallel one used on the Datamaster) and a new external housing.