An argument of an operator or of a machine language instruction.

Last updated: 1995-08-18


1. operating system.

2. operator.

operating system

<operating system>

(OS) The low-level software which handles the interface to peripheral hardware, schedules tasks, allocates storage, and presents a default interface to the user when no application program is running.

The OS may be split into a kernel which is always present and various system programs which use facilities provided by the kernel to perform higher-level house-keeping tasks, often acting as servers in a client-server relationship.

Some would include a graphical user interface and window system as part of the OS, others would not. The operating system loader, BIOS, or other firmware required at boot time or when installing the operating system would generally not be considered part of the operating system, though this distinction is unclear in the case of a rommable operating system such as RISC OS.

The facilities an operating system provides and its general design philosophy exert an extremely strong influence on programming style and on the technical cultures that grow up around the machines on which it runs.

Example operating systems include 386BSD, AIX, AOS, Amoeba, Angel, Artemis microkernel, BeOS, Brazil, COS, CP/M, CTSS, Chorus, DACNOS, DOSEXEC 2, GCOS, GEORGE 3, GEOS, ITS, KAOS, Linux, LynxOS, MPV, MS-DOS, MVS, Mach, Macintosh operating system, Microsoft Windows, MINIX, Multics, Multipop-68, Novell NetWare, OS-9, OS/2, Pick, Plan 9, QNX, RISC OS, STING, System V, System/360, TOPS-10, TOPS-20, TRUSIX, TWENEX, TYMCOM-X, Thoth, Unix, VM/CMS, VMS, VRTX, VSTa, VxWorks, WAITS.


Usenet newsgroup: comp.os.research.

[Jargon File]

Last updated: 1999-06-09

Operating System/360

<operating system>

(OS/360) An operating system developed by IBM for their System/360 computer (announced in 1964).

After this experience, Frederick P. Brooks wrote his famous book, The Mythical Man-Month, giving OS/360 as an example of the second-system effect.

[Features? Relatonship to DOS/360?]

Last updated: 2001-03-23

Operating System/Multiprogramming of Fixed Tasks

<operating system>

(OS/MFT) One of the IBM operating systems associated with the IBM 360, released in 1966 and targetted at mid-range IBM 360 users (typically 360/40, 360/50). OS/MFT was the juinior member of the main 'OS' series of IBM operating systems, the other being OS/MVT. Smaller 360 mainframes used DOS.

OS/MFT shared JCL and utilities with OS/MVT but allocated memory differently. In OS/MFT, partitions of memory were of a fixed number and size, specified by the generation and configuration of the operating system. As this class of mainframe had typically less than 512K of main memory, partitions tended to be about 128K.

With the advent of Virtual Storage and the System 370's Dynamic Address Translation (DAT), OS/MFT was improved to become OS/VS1, taking account of virtual storage in a single partition up to 16MB.

Last updated: 1999-01-22

operational database


A database containing up-to-date, modifiable data, in contrast to a decision support database.

Last updated: 1995-02-14

Operational Data Store


(ODS) A group of integrated databases designed to support the monitoring of operations. Unlike function oriented databases, an ODS contains subject-oriented, dynamic, current enterprise-wide information that is continually updated to show the current state of operations.

["Data Warehousing Architecture and Implementation"].

Last updated: 2010-02-28

operational requirements


Qualitative and quantitative parameters that specify the desired capabilities of a system and serve as a basis for determining the operational effectiveness and suitability of a system prior to deployment.

Last updated: 1997-01-07

operational semantics


A set of rules specifying how the state of an actual or hypothetical computer changes while executing a program. The overall state is typically divided into a number of components, e.g. stack, heap, registers etc. Each rule specifies certain preconditions on the contents of some components and their new contents after the application of the rule.

It is similar in spirit to the notion of a Turing machine, in which actions are precisely described in a mathematical way.

Compuare axiomatic semantics, denotational semantics.

Last updated: 1996-08-21

operational test and evaluation


(OT&E) Formal testing conducted prior to deployment to evaluate the operational effectiveness and suitability of the system with respect to its mission.

Last updated: 1997-01-07

operational testing


A US DoD term for testing performed by the end-user on software in its normal operating environment.

Last updated: 1997-01-07

operation code


(Always "op code" when spoken) The part or parts of a machine language instruction which determines what kind of action the computer should take, e.g. add, jump, load, store. In any particular instruction set certain fixed bit positions within the instruction word contain the op code, others give parameters such as the addresses or registers involved. For example, in a 32-bit instruction the most significant eight bits might be the op code giving 256 possible operations.

For some instruction sets, certain values in the fixed bit positions may select a group of operations and the exact operation may depend on other bits within instruction word or subsequent words.

When programming in assembly language, the op code is represented by a readable name called an instruction mnemonic.

Last updated: 1997-02-14

operations support technician


A person who analyses and supports computer operations by controlling production applications, monitoring system resources and response time and providing first-line support for operational problems.

Last updated: 2004-03-20



A symbol used as a function, with infix syntax if it has two arguments (e.g. "+") or prefix syntax if it has only one (e.g. Boolean NOT). Many languages use operators for built-in functions such as arithmetic and logic.

Last updated: 1995-04-30

Operator Control Language


(OCL) The batch language for the IBM System/36, used specifically with the RPG II compiler.

See also CL.

Last updated: 1994-11-18

operator overloading


Nearby terms:

OpenVMSOpenWindowsoperandoperatingoperating systemOperating System/360

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