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Early computers were built to perform a series of single tasks, like a calculator. Operating systems did not exist in
their modern and more complex forms until the early 1960s. Some operating system features were developed in
the 1950s, such as monitor programs that could automatically run different application programs in succession to
speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel
processing. When personal computers by companies such as Apple Inc., Atari, IBM and Amiga became popular in
the 1980s, vendors added operating system features that had previously become widely used on mainframe and
mini computers. Later, many features such as graphical user interface were developed specifically for personal
computer operating systems.
An operating system consists of many parts. One of the most important components is the kernel, which controls
low-level processes that the average user usually cannot see: it controls how memory is read and written, the order
in which processes are executed, how information is received and sent by devices like the monitor, keyboard and
mouse, and decides how to interpret information received from networks. The user interface is a component that
interacts with the computer user directly, allowing them to control and use programs. The user interface may be
graphical with icons and a desktop, or textual, with a command line. Application programming interfaces provide
services and code libraries that let applications developers write modular code reusing well defined programming
sequences in user space libraries or in the operating system itself. Which features are considered part of the
operating system is defined differently in various operating systems. For example, Microsoft Windows considers its
user interface to be part of the operating system, while many versions of Linux do not.
Main article: History of operating systems
In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer
and would arrive at a scheduled time with program and data on punched paper cards and tape. The program would
be loaded into the machine, and the machine would be set to work until the program completed or crashed.
Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan
12/31/2010 Operating system - Wikipedia, the free …
OS/360 was used on most IBM
mainframe computers beginning in
1966, including the computers that
helped NASA put a man on the
Turing was a master of this on the early Manchester Mark 1 machine,
and he was already deriving the primitive conception of an operating
system from the principles of the Universal Turing
Later machines came with libraries of software, which would be linked to
a user's program to assist in operations such as input and output and
generating computer code from human-readable symbolic code. This was
the genesis of the modern-day operating system. However, machines still
ran a single job at a time. At Cambridge University in England the job
queue was at one time a washing line from which tapes were hung with
different colored clothes-pegs to indicate job-priority.
For more details on IBM mainframe operating systems, see
History of IBM mainframe operating systems.
Through the 1950s, many major features were pioneered in the field of
operating systems, including batch processing, input/output interrupt,
buffering, multitasking, spooling, runtime libraries, link-loading, and
programs for sorting records in files. These features were included or not
included in application software at the option of application programmers, rather than in a separate operating system
used by all applications. In 1959 the SHARE Operating System was released as an integrated utility for the IBM
704, and later in the 709 and 7090 mainframes.
During the 1960s, IBM's OS/360 introduced the concept of a single OS spanning an entire product line, which was
crucial for the success of the System/360 machines. IBM's current mainframe operating systems are distant
descendants of this original system and applications written for OS/360 can still be run on modern
machines. In the mid-'70s, MVS, a descendant of OS/360, offered the first
implementation of using RAM as a transparent cache for data.
OS/360 also pioneered the concept that the operating system keeps track of all of the system resources that are
used, including program and data space allocation in main memory and file space in secondary storage, and file
locking during update. When the process is terminated for any reason, all of these resources are re-claimed by the
The alternative CP-67 system for the S/360-67 started a whole line of IBM operating systems focused on the
concept of virtual machines. Other operating systems used on IBM S/360 series mainframes included systems
developed by IBM: DOS/360 (Disk Operating System), TSS/360 (Time Sharing System), TOS/360 (Tape
Operating System), BOS/360 (Basic Operating System), and ACP (Airline Control Program), as well as a few
non-IBM systems: MTS (Michigan Terminal System) and MUSIC (Multi-User System for Interactive Computing).
Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In
cooperation with the University of Minnesota, the KRONOS and later the NOS operating systems were developed
during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing
systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in
timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the
12/31/2010 Operating system - Wikipedia, the free …
PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was
remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. Burroughs Corporation
introduced the B5000 in 1961 with the MCP, (Master Control Program) operating system. The B5000 was a
stack machine designed to exclusively support high-level languages with no machine language or assembler, and
indeed the MCP was the first OS to be written exclusively in a high-level language – ESPOL, a dialect of ALGOL.
MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation
of virtual memory. During development of the AS400, IBM made an approach to Burroughs to licence MCP to run
on the AS400 hardware. This proposal was declined by Burroughs management to protect its existing hardware
production. MCP is still in use today in the Unisys ClearPath/MCP line of computers.
UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all
early main-frame systems, this was a batch-oriented system that managed magnetic drums, disks, card readers and
line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time
sharing, also patterned after the Dartmouth BC system.
General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which
introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed to General
Comprehensive Operating System (GCOS).
Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-
10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Prior to the widespread use of UNIX,
TOPS-10 was a particularly popular system in universities, and in the early ARPANET community.
In the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported
software to run on more than one system. Early systems had utilized microprogramming to implement features on
their systems in order to permit different underlying architecture to appear to be the same as others in a series. In
fact most 360's after the 360/40 (except the 360/165 and 360/168) were microprogrammed implementations. But
soon other means of achieving application compatibility were proven to be more significant.
The enormous investment in software for these systems made since 1960s caused most of the original computer
manufacturers to continue to develop compatible operating systems along with the hardware. The notable
supported mainframe operating systems include:
Burroughs MCP – B5000, 1961 to Unisys Clearpath/MCP, present.
IBM OS/360 – IBM System/360, 1966 to IBM z/OS, present.
IBM CP-67 – IBM System/360, 1967 to IBM z/VM, present.
UNIVAC EXEC 8 – UNIVAC 1108, 1967, to OS 2200 Unisys Clearpath Dorado, present.