MINIMOP was an
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
which ran on the
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 Ele ...
(ICL)
1900 series of computers. MINIMOP provided an
on-line
In computer technology and telecommunications, online indicates a state of connectivity and offline indicates a disconnected state. In modern terminology, this usually refers to an Internet connection, but (especially when expressed "on line" or ...
,
time-sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1
Its emergence a ...
environment (Multiple Online Programming, or MOP in ICL terminology), and typically ran alongside
George 2
GEORGE was the name given to a series of operating systems released by International Computers and Tabulators (ICT) in the 1960s, for the ICT 1900 series of computers. These included GEORGE 1, GEORGE 2, GEORGE 3, and GEORGE 4.
Initially the 19 ...
running
batch jobs.
[ MINIMOP was named to reflect its role as an alternative to the MOP facilities of ]George 3
GEORGE was the name given to a series of operating systems released by International Computers and Tabulators (ICT) in the 1960s, for the ICT 1900 series of computers. These included GEORGE 1, GEORGE 2, GEORGE 3, and GEORGE 4.
Initially the 19 ...
, which required a more powerful machine.
MINIMOP would run on all 1900 processors apart from the low-end 1901 and 1902 and required only 16K words of memory and two 4 or 8 million character magnetic disks.
Each user was provided with a fixed size file to hold his data, which was subdivided into a number of variable sized ''subfiles''. The command language could be extended with simple macros.
Implementation
MINIMOP was implemented as a multithreaded (sub-programmed in ICL terminology) user level program running on the standard ''executive'' (low level operating system) of the ICL 1900. The ''program under control'' facilities of executive were used to run user programs under MINIMOP. All user I/O operations were trapped by MINIMOP and emulated rather than accessing real peripherals. As memory was at a premium user programs would be swapped out of memory whenever they needed to wait (for input or output) or when they reached the end of their time slice
In computing, preemption is the act of temporarily interrupting an executing task, with the intention of resuming it at a later time. This interrupt is done by an external scheduler with no assistance or cooperation from the task. This preempt ...
.
MAXIMOP
Queen Mary College, London, now Queen Mary, University of London
, mottoeng = With united powers
, established = 1785 – The London Hospital Medical College1843 – St Bartholomew's Hospital Medical College1882 – Westfield College1887 – East London College/Queen Mary College
, type = Public researc ...
, later developed MAXIMOP, an improved system largely compatible with MINIMOP.
References
ICL operating systems
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