In 1972, Gary Kildall, an instructor at the Naval Postgraduate School in Monterey, California, began working at Intel as a consultant under the business name Microcomputer Applications Associates (MAA).

[11] The company's documentation had a poor reputation, with Jerry Pournelle in 1982 describing it as seemingly "encrypted and translated into Swahili".

[14] It remained influential, with US$45 million in 1983 sales making Digital Research the fourth-largest microcomputer software company.

"[16] In a parallel development Digital Research also produced a selection of programming language compilers and interpreters for their OS-supported platforms, including C, Pascal, COBOL, FORTRAN, PL/I, PL/M, CBASIC, BASIC, and Logo.

[citation needed] Microsoft seized this opportunity to supply an OS, in addition to other software (e.g., BASIC) for the new IBM PC.

This practice led to a US Department of Justice investigation, resulting in a decision in 1994 that barred Microsoft from "per-processor" licensing.

[19] Successive revisions of Concurrent CP/M incorporated MS-DOS API emulation (since 1983), which gradually added more support for DOS applications and the FAT file system.

[citation needed] In 1985, soon after the introduction of the 80286-based IBM PC/AT, Digital Research introduced a real-time system, initially called Concurrent DOS 286.

In order to achieve this, it gave up built-in support to run CP/M applications and was changed to use DOS-compatible internal structures.

[citation needed] In 1985 Digital Research also produced a microcomputer version of the GKS graphics standard (related to NAPLPS) called GSX, and later used this as the basis of their GEM GUI.

Digital Research (and later its successor Caldera) accused Microsoft of announcing vaporware versions of MS-DOS to suppress sales of DR DOS.