Direct Machine Environment, abbreviated DME, was a

mainframe A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

environment for the

ICL 2900 Series The ICL 2900 Series was a range of mainframe computer systems announced by the British manufacturer ICL on 9 October 1974. The company had started development under the name "New Range" immediately on its formation in 1968. The range was not de ...

of computing systems from

International Computers Limited International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that operated from 1968 until 2002. It was formed through a merger of International Computers and Tabulators (ICT), English ...

that was developed in the 1970s. DME was more-or-less an

ICL 1900 ICT 1900 was a family of mainframe computers released by International Computers and Tabulators (ICT) and later International Computers Limited (ICL) during the 1960s and 1970s. The 1900 series was notable for being one of the few non-American c ...

order code processor in

microcode In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a la ...

, which permitted the ICL 1900 series executive,

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

s and

program libraries In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subr ...

to operate on the ICL 2900 series.

Reason for Development

At this time most companies that had computers had large teams of programmers to write their applications. DME was developed so that customers could buy the new hardware and run their 1900 or System 4 applications whilst they developed their replacement VME applications. This led to some users running DME and VME alternately on the same machine for some years. Unfortunately this led to situations where development teams were waiting around for time to run their new applications. This, and the fact that some users were not moving to the new system, led ICL to develop a system called Concurrent Machine Environment (CME) under which VME ran DME as a subsystem, enabling 1900 and System 4 applications to be run on a 2900 or Series 39 machine alongside VME applications.

References

Direct Machine Environment {{operating-system-stub