The company's operating systems, starting with CP/M for 8080/Z80-based microcomputers, were the de facto standard of their era, as MS-DOS and MS Windows became later. DR's product suite included the original CP/M and its various offshoots; DR-DOS which was a MS-DOS compatible version of CP/M, and MP/M, the multi-user CP/M. The first 16-bit system was CP/M-86, which was to be unsuccessful in competition with MS-DOS. There followed Concurrent CP/M, a single-user version of the multi-tasking MP/M-86 featuring "virtual consoles" from which applications could be launched to run concurrently. Successive revisions of this system, which gradually supported MS-DOS applications and the FAT filesystem, were labelled Concurrent DOS, Concurrent DOS XM and Concurrent DOS 386.
Soon after the introduction of the Intel 80286, DR introduced a radical new real-time system, initially called DOS-286 and subsequently Flex OS. This exploited the greater memory addressing capability of the new CPU to provide a more flexible multi-tasking environment. There was a small but powerful set of system APIs, each with a synchronous and an asynchronous variant. Pipes were supported, and all named resources could be aliased by setting Environment variables. This system was to enjoy enduring favour in point-of-sale systems and was adopted by the IBM 4690 OS.
DR produced a selection of programming language compilers and interpreters for their OS-supported platforms, including C, Pascal, COBOL, Forth, PL/I, PL/M, BASIC, and Logo. They 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. Less known are their application programs, limited largely to the GSX-based DR-DRAW and a small suite of GUI programs for GEM.
When the IBM Personal Computer was being developed, DR was asked to supply a version of CP/M written for the Intel 8086 microprocessor as the standard operating system for the PC, which used the code-compatible Intel 8088 chip. DR, which had the dominant OS system of the day, was uneasy about the agreement with IBM and refused, Microsoft seized this opportunity to supply the OS in addition to other software (e.g. Basic) for the new IBM PC. When the IBM PC arrived in late 1981, it came with PC-DOS, which was developed from 86-DOS, which Microsoft acquired for this purpose. By mid-1982, it was marketed as MS-DOS for use in hardware compatible non-IBM computers. This one decision resulted in Microsoft becoming the leading name in computer software. This story is detailed in the PBS series Triumph of the Nerds
Digital Research developed CP/M-86 as an alternative to MS-DOS and it was made available through IBM in early 1982. DR later created an MS-DOS clone with advanced features called DR-DOS, which pressured Microsoft to further improve its own DOS. The competition between MS-DOS and DR-DOS is one of the more controversial chapters of microcomputer history. Microsoft offered the best licensing terms to computer manufacturers that committed to selling MS-DOS with every processor they shipped, making it uneconomical for them to offer both systems. This practice led to a 1994 government antitrust lawsuit against Microsoft that barred it from per-processor licensing. DRI (and later its successor Caldera Systems) accused Microsoft of announcing vaporware versions of MS-DOS to suppress sales of DR-DOS. Microsoft refused to support DR-DOS in Windows; in one beta release of Windows, Microsoft included code that detected DR-DOS and displayed a warning message. DRI's successor Caldera Systems raised these disputes in a 1996 lawsuit, but the case was settled without a trial. As a condition of the settlement Microsoft paid Caldera $150 million and Caldera destroyed all documents it had produced in connection with the case.