thumb|Closeup of a running 5120
The IBM 5120 Computing System (sometimes referred to as the IBM 5110 Model 3) is a 16-bit microcomputer developed by IBM and released in February 1980. Marketed as the desktop follow-on to the portable IBM 5110 Computing System, it featured two built-in 8-inch 1.2 MB floppy disk drives, an integrated 9-inch monochrome monitor, 32 KB RAM, plus an optional IBM 5114 stand-alone diskette unit with two additional 8-inch 1.2 MB floppy disk drives.
The system was sold with both APL and BASIC languages in ROM, and provided a toggle switch on the front panel to select the language. APL allowed numerous business software written on IBM minicomputers to run on the 5120.
Description
It was launched in 1980 as the lowest-priced IBM business computer to date. Depending on the options the overall system prices ranged from $9,340 to $23,990. To emphasize its office image IBM released six new programs that year: task inventory, billing, payroll, accounts payable, accounts receivable and general ledger accounting.
IBM did not offer a LAN or hard disk drive for these systems. However, in 1981, Hal Prewitt, founder of Core International, Inc, invented and marketed the world's first and only hard disk subsystems and "CoreNet", a LAN used to share programs and data for the IBM 5110 and 5120 systems. In 1984, Core introduced PC51, software that ran unmodified 5100 Series computer programs written in BASIC on the IBM PC and compatibles under PC DOS and shared programs and data on CoreNet, the LAN for all these models.
The 5120 was withdrawn from marketing on 10 December 1982.