CP/M (Control Program for Microcomputers) was essentially the first operating system for hobbyists and small businesses, dominating the 8-bit microcomputer market in the late 1970s and early 1980s. Created by Gary Kildall in 1974, it provided file management, program loading, and hardware abstraction, making micros practical for real work. Its portability across hardware platforms fueled its success, though it was eventually eclipsed by MS-DOS.
Gary Kildall developed CP/M in 1974 while consulting for Intel on the 8080 microprocessor. Frustrated by the lack of a disk operating system for the new chips, he wrote CP/M initially for his own use on an Intellec-8 development system. It was a simple DOS for managing floppy disks, inspired by DEC's minicomputer OSes. Kildall founded Digital Research Inc. (DRI) with his wife Dorothy in 1976 to commercialize it. The first version shipped in 1974, with refinements leading to CP/M 1.3 in 1975. Intel declined to buy it for $20,000, allowing DRI to market it widely.
DRI officially sold around 250,000 licenses, but due to widespread piracy and unlicensed copies, estimates suggest millions of installations worldwide. By the early 1980s, CP/M was on over half of all microcomputers, generating tens of millions in revenue for DRI.
CP/M ran on over 200 different hardware platforms from dozens of manufacturers, including Altair 8800, IMSAI 8080, Osborne 1, Kaypro II, TRS-80 Model II, and many S-100 bus systems. It supported hundreds of models, making it the de facto standard for 8-bit business and hobbyist machines before the IBM PC.
CP/M was actively used from 1974 to the mid-1980s, with peak popularity 1978-1983. Legacy support continued into the 1990s on embedded systems and clones. It spanned about 15-20 years of widespread use before MS-DOS dominance.
DRI released several versions: CP/M 1.3 (1975), 1.4 (1976), 2.0 (1979), 2.2 (1980, most popular), and 3.0 (1983, known as CP/M Plus with banking and improved performance). Variants like MP/M (multi-user) and CP/M-86 (for 8086) extended the family.
In 1980, IBM approached DRI for CP/M-86 for the upcoming PC. Legend says Kildall missed the meeting (flying his plane), leaving his wife and lawyers to negotiate. In reality, talks failed over terms: DRI wanted royalties per copy ($10/unit), while IBM demanded a flat fee ($310,000 total) and non-disclosure. Licensing issues and IBM's secrecy clashed with DRI's open model. IBM turned to Microsoft, who acquired 86-DOS from Seattle Computer Products for $75,000 and adapted it into PC-DOS/MS-DOS. Kildall later claimed DOS copied CP/M's API, but a lawsuit settled out of court.
The original CP/M license cost around $150 for end-users (OEMs paid less for bundling). Minimal hardware: Intel 8080 or Z80 CPU, at least 16 KB RAM (48-64 KB realistic for useful operation), a console terminal (ASCII keyboard/CRT), and at least one floppy disk drive (typically 8-inch, 77 KB single-density).