IMDOS was a modified version of the CP/M

CP/M

CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...

 operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 for Intel 8080

Intel 8080

The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility...

 processors, used by IMS Associates, Inc.

IMS Associates, Inc.

IMS Associates, Inc., or IMSAI, was a microcomputer company, responsible for one of the earliest successes in personal computing, the IMSAI 8080. The company was founded in 1973 by William Millard and was based in San Leandro, California. Their first product launch was the IMSAI 8080 in 1975. One...

 (IMS) for their IMSAI 8080

IMSAI 8080

The IMSAI 8080 was an early microcomputer released in late 1975, based on the Intel 8080 and later 8085 and S-100 bus. It was a clone of its main competitor, the earlier MITS Altair 8800. The IMSAI is largely regarded as the first "clone" computer. The IMSAI machine ran a highly modified version of...

 personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

. Since MITS

Micro Instrumentation and Telemetry Systems

Micro Instrumentation and Telemetry Systems was an American electronics company founded in Albuquerque, New Mexico that began manufacturing electronic calculators in 1971 and personal computers in 1975. Ed Roberts and Forrest Mims founded MITS in December 1969 to produce miniaturized telemetry...

 would not license their operating system to other manufacturers, IMS approached Gary Kildall

Gary Kildall

Gary Arlen Kildall was an American computer scientist and microcomputer entrepreneur who created the CP/M operating system and founded Digital Research, Inc....

and paid a fixed fee of $25,000 for non-exclusive CP/M license.

IMDOS introduced interrupt-driven devices, tree-structured directories, and other advances to CP/M.