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_Operating Systems _
By: Anonymous
Operating Systems An operating system is the program that manages all the
application programs in a computer system. This also includes managing the
input and output devices, and assigning system resources. Operating systems
evolved as the solution to the problems that were evident in early computer
systems, and coincide with the changing computer systems. Three cycles are
clear in the evolution of computers, the mainframe computers, minicomputers
and microcomputers, and each of these stages influenced the development of
operating systems. Now, advances in software and hardware technologies have
resulted in an increased demand for more sophisticated and powerful operating
systems, with each new generation able to handle and perform more complex
tasks. The folowing report examines the development of operating systems, and
how the changing tehcnology shaped the evolution of operating systems. First
Generation Computers (1945Ó1955) In the midÓ1940's enormous machines capable
of performing numerical calculations were created. The machine consisted of
vacuum tubes and plugboards, and programming was done purely in machine code.
Programming languages were unheard of during the early part of the period, and
each machine was specifically assembled to carry out a particular calculation.
These early computers had no need for an operating system and were operated
directly from the operator's console by a computer programmer, who had
immediate knowledge of the computers design. By the early 1950's punched cards
were introduced, allowing programs to be written and read directly from the
card, instead of using plugboards. Second Generation Computers (1955Ó1965) In
the midÓ1950's, the transistor was introduced, creating a more reliable
computer. Computers were used primarily for scientific and engineering
calculations and were programmed mainly in FORTRAN and assembly language. As
computers became more reliable they also became more business orientated,
although they were still very large and expensive. Because of the expenditure,
the productiveness of the system had to be magnified as to ensure cost
effectiveness. Job scheduling and the hiring of computer operators, ensured
that the computer was used effectively and crucial time was not wasted.
Loading the compliers was a time consuming process as each complier was kept
on a magnetic tape, which had to be manually mounted. This became a problem
particularly when there were multiple jobs to execute written in different
languages (mainly in Assembly or Fortran). Each card and tape had to
individually be installed, executed then removed for each program. To combat
this problem, the Batch System was developed. This meant that all the jobs
were grouped into batches and read by one computer (usually an IBM 1401) then
executed one after the other on the mainframe computer (usually an IBM 7094),
eliminating the need to swap tapes or cards between programs. The first
operating system was designed by General Motors for the IBM 701. It was called
Input/Output System, and consisted of a small set of code that provided a
common set of procedures to be used to access the input and output devices. It
also allowed each program to access the code when finished and accepted and
loaded the next program. However, there was a need to improve the sharing of
programs, which led to the development of the SOS (Share operating system), in
1959. The SOS provided buffer management and supervision for I/O devices as
well as support for programming in assembly language. Around the same time as
SOS was being developed, the first operating system to support programming in
a highÓlevel language was achieved. FMS (Fortran Monitoring System)
incorporated a translator for IBM's FORTRAN language, which was widely used as
most programs where written in this language. Third Generation Computers
(1965Ó1980) In the late 1960's IBM created the System/360 which was a series
of software compatible computers ranging in different power of performance and
price. The machines had the same architecture and instruction set, which
allowed programs written for one machine to be executed on another. The
operating system required to run on this family of computers has to be able to
work on all models, be backwards compatible and be able to run on both small
and large systems. The software written to handle these different requirements
was OS/360, which consisted of millions of lines of assembly language written
by thousands of different programmers. It also contained thousands of bugs,
but despite this the operating system satisfactory fulfilled the requirements
of most users. A major feature of the new operating system was the ability to
implement multiprogramming. By partitioning the memory into several pieces,
programmers where able to use the CPU more effectively then ever before, as a
job could be processed whilst another was waiting for I/O to finish. Spooling
was another important feature implemented in third generation operating
systems. Spooling (Simultaneous Peripheral Operation OnÓLine) was is ability
to load a new program into an empty partition of memory when a pervious job
had finished. This technique meant that the IBM 1401 computer was no longer
required to read the program from the magnetic tape. mission of a job and
returning of results had increased. This led designers to the concept of
timeÓsharing, which involved each user communicating with the computer through
an their own onÓline terminal. The SPU could only be allocated to 3 terminals,
each job held in a partition of memory. Many timeÓsharing operating systems
were introduced in the 1960's, including the MULTICS (Multiplexed Information
and Computing Service). Developed by Bell Labs, MULTICS was written almost
completely in highÓlevel language, and is known as the first major operating
system to have done so. MULTICS examined many new concepts including segmented
memory, device independence, hierarchal file system, I/O redirection, a
powerful user interface and protection rings. The 1960's also gave rise to the
minicomputer, starting with the DEC PDPÓ1. Minicomputers presented the market
with an affordable alternative to the large batch systems of that time, but
had only a small amount of memory. The early operating system of the
minicomputers were Input/Output selectors, and provided an interactive user
interface for a single user, and ran only one program at a time. By the
1970's, DEC introduced a new family of minicomputers. The PDPÓ11 series had 3
operating systems available to use on the systems, a simple single user system
(RTÓ11), a time sharing system (RSTS) and a realÓtime system (RSXÓ11). RSXÓ11
was the most advanced operating system for the PDPÓ11 series. It supported a
powerful command language and file system, memory management and
muiltprogramming a number of tasks. Around the same time as DEC were
implementing their minicomputers, two researchers, ken Thomspson and Dennis
Richie were developing a new operating system for the DEC PDPÓ7. Their aim was
to create a new singleÓuser operating, and the first version was officially
released in 1971. This operating system, called UNIX became very popular and
is still used widely today. Fourth Generation Computers (1980Ó1990) By the
1980's, technology had advanced a great deal from the days of the mainframe
computers and vacuum tubes. With the introduction of Large Scale Integration
circuits (LSI) and silicon chips consisting of thousands of transistors,
computers reached a new level. Microcomputers, which were physically much like
the minicomputers of the third generation, however they were much cheaper
enabling individuals to now use them, not just large company's and
universities. These personal computers and required an operating system that
was user friendly so that people with little computer knowledge was able to
use it. In 1981, IBM was releasing a 16Óbit personal computer, and required a
more powerful operating system then the ones available at the time, so they
turned to Microsoft to deliver it. The software, called Micro Soft Disk
Operating System (MSÓDOS) became the standard operating system for most
personal computers of that era. In the midÓ1980's, networks of personal
computers had increased a great deal, requiring a new type of operating
system. The OS had to be able to manage remote and local hardware and
software, file sharing and protection, among other things. Two types of
systems were introduced, the network operating system in which users can copy
from one station to another, and the distributed operating system, in which
the computer appears to be a uniÓprocessor system, even though it is actually
running programs and storing files in a remote location. One of the best known
network operating system for a distributed network is the Network File System
(NFS), which was originally designed by Sun Microsystems, for use on UNIX
based machines. An important feature of the NFS is its ability to support
different type of computers. This allowed a machine running NFS to communicate
with an IBM compatible machine running MSÓDOS, which was an important addition
to networking computing. In 1983, Microsoft Corporation introduced the
MSXÓDOS, an operating system for MSX microcomputers that can run 8Óbit
Microsoft software including the languages BASIC, COBOLÓ80, and FORTRANÓ80,
and Multiplan. 1984 saw the release of the Apple Macintosh, a lowÓcost
workstation, which evolved from early Alto computer designs. The Macintosh
provided advanced graphics and high performance for its size and cost. As the
Macintosh was not compatible with other systems, it required its own operating
system, which is how the Apple operating system was established. MIMIX, based
on the UNIX design was also a popular choice for the Macintosh. As computer
processors got faster, operating systems also had to improve in order to take
advantage of this progression. Microsoft released version 2 of MSÓDOS, which
adopted the many features that made UNIX so popular, although MSÓDOS was
designed to be smaller then, but was not as large as the UNIX operating system
making it ideal for personal computers. Modern Operating Systems The past 9
years have seen many advances in computers and their operating systems.
Processors continue to increase in speed, each requiring an operating system
to handle the new developments. Microsoft Corporation has dominated the IBM
compatible world, Windows being the standard operating system for majority of
personal computers. Now as computing and information technology becomes more
towards the Internet and virtual computing, so too must the operating systems.
In 1992, Microsoft for Workgroups 3.1 was introduced, extending on from the
previous versions. It allowed the sending of electronic mail, and provided
advanced networking capabilities to be used as a client on an existing local
area network. This was only the one stage in the vast evolution of the worlds
most popular operating system, with the most recent being Windows NT and
Windows 98, the latter being a fully Internet integrated operating system.
Windows, however is not the only operating system in use today. Other's such
as UNIX, Apple Operating System and OS/Warp have also had an impact, each new
version more advanced, and more user friendly then the last.
Word Count: 1774
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