Multiuser DOS - Concurrent CP/M-86

Concurrent CP/M-86

The initial version of CP/M for the IBM PC, CP/M-86, was commercially unsuccessful, as Microsoft's MS-DOS offered much the same facilities for a considerably lower price. Like MS-DOS 1.0, CP/M-86 did not fully exploit the power and capabilities of the new 16-bit machine.

It was soon superseded by an implementation of CP/M's multitasking 'big brother', MP/M-86. This turned a PC into a multiuser machine capable of supporting multiple concurrent users using dumb terminals attached by serial ports. The environment presented to each user made it seem as if they had the entire computer to themselves. Since terminals cost a fraction of the then-substantial price of a complete PC, this offered considerable cost savings, as well as facilitating multi-user applications such as accounts or stock control in a time when PC networks were rare, very expensive and difficult to implement.

CP/M-86 and MP/M-86 were later merged to create Concurrent CP/M-86 (also known as CCP/M-86 with BDOS 3.0), which offered CP/M-86 compatibility in conjunction with MP/M-86's multiuser capabilities. Concurrent CP/M-86 3.1 (BDOS 3.1) shipped on 21 February 1984.