Data General RDOS

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DeveloperData General
OS familyData General
Working stateDiscontinued
Source modelClosed source
Initial release1972; 46 years ago (1972)
Latest releaseRDOS 7.5 / 1986; 32 years ago (1986)
PlatformsNOVA, microNOVA, Eclipse
Kernel typeMonolithic
Default user interfaceCLI
Licenserestricted, per machine

The Data General RDOS (Real-time Disk Operating System) was a real-time operating system released in 1970.[1] The software was only sold bundled with the company's popular Nova and Eclipse minicomputers.[2]

RDOS was capable of multitasking, with the ability to run up to 32 what were called "tasks" (similar to the current term threads) simultaneously on each of two grounds (foreground and background) within a 64 KB memory space. Later versions of RDOS were compatible with Data General's 16-bit Eclipse minicomputer line.[3]

A cut-down version of RDOS, without real-time background and foreground capability but still capable of running multiple threads and multi-user Data General Business Basic, was called Data General Diskette Operating System[4] (DG-DOS or, now somewhat confusingly, simply DOS); another related operating system was RTOS, a Real-Time Operating System for diskless environments. RDOS on microNOVA-based "Micro Products" micro-minicomputers was sometimes called DG/RDOS.[5]

RDOS was superseded in the early 1980s by Data General's AOS family of operating systems, including AOS/VS and MP/AOS (MP/OS on smaller systems).

Antitrust lawsuit[edit]

In the late 1970s Data General was sued (under the Sherman and Clayton antitrust acts)[6] by competitors for their practice of bundling RDOS with the Data General Nova or Eclipse minicomputer.[7] When Data General introduced the Data General Nova, a company called Digidyne wanted to use its RDOS operating system on its own hardware clone. Data General refused to license their software and claimed their "bundling rights". In 1985, courts including the United States Court of Appeals for the Ninth Circuit ruled against Data General in a case called Digidyne v. Data General. The Supreme Court of the United States declined to hear Data General's appeal, although Justices White and Blackmun would have heard it. The precedent set by the lower courts eventually forced Data General to license the operating system because restricting the software to only Data General's hardware was an illegal tying arrangement.[8]

In 1999, Data General was taken over by EMC Corporation.[9]


  1. ^ The Electronic Engineer: EE. Chilton Company. 1969.
  2. ^ Computer Law Reporter. Computer Law Reporter Incorporated. 1986.
  3. ^ Sidney W. Frost; James C. Dunlap (1983). Automated law office systems: a survey of today's tools and techniques. West Pub. Co.
  4. ^ IDG Enterprise (9 July 1975). Computerworld. IDG Enterprise. pp. 18–. ISSN 0010-4841.
  5. ^ Trade Cases. Commerce Clearing House. 1987.
  6. ^ Santa Clara computer and high-technology law journal. 1986.
  7. ^ "In Re Data General Corp. Antitrust Litigation, 529 F. Supp. 801 (N.D. Cal. 1981)". Justia. Retrieved 26 December 2016.
  8. ^ "Tying Arrangements and the Computer Industry: Digidyne Corp. vs. Data General". JSTOR 1372482. Missing or empty |url= (help)
  9. ^ InfoWorld Media Group, Inc. (16 August 1999). InfoWorld. InfoWorld Media Group, Inc. pp. 12–. ISSN 0199-6649.

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