CP/M (Control Program for Microcomputers) is an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc. Initially confined to single-tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations, and were migrated to 16-bit processors.

The combination of CP/M and S-100 bus computers patterned on the MITS Altair was an early "industry standard" for microcomputers, and this computer platform was widely used in business through the late 1970s and into the mid-1980s. By greatly reducing the amount of programming required to install an application on a new manufacturer's computer, CP/M increased the market size for both hardware and software.

Source: Wikipedia, "CP/M," available under the CC-BY-SA License.