CECS 410 Computers and Networks
Operating Systems – Part 1
Operating System Overview
Defn: The operating system (OS) is the software that manages the
way other programs run on the computer. The OS controls all
peripheral devices attached to a computer and handles
communication between the user and the computer.
1964 OS/360 For IBM 360 Computers
1964 DOS/360 DOS for IBM 360 Computers
1969 Unix First Unix OS
1978 Apple DOS3.1 First Apple OS
1981 MS DOS Microsoft’s DOS
1984 Mac OS 1.0 First Mac OS
1985 MS Windows 1.0 First Windows OS
1991 Linux First Linux
1995 Windows 95
1997 Mac OS 7.6
1998 Windows 98
2000 Windows 2000/Me
2001 Windows XP
2001 Mac OS X Based on Unix approach
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DOS for IBM PC compatibles (From Wikipedia, the free encyclopedia.)
In particular, DOS refers to the family of closely related operating systems
which dominated the IBM PC compatible market for the decade between
1985 and 1995: PC-DOS, MS-DOS, DR-DOS, FreeDOS, OpenDOS, PTS-
DOS, and several others. Of these, MS-DOS from Microsoft became the
most widely used.
MS-DOS (and the IBM PC-DOS which was licensed therefrom), and its
predecessor, QDOS, was a successor to CP/M (Command Processor / (for)
Microcomputers)—which was the dominant operating system for 8-bit
Intel 8080 and Zilog Z80 based microcomputers.
DOS was one of the first operating systems for the PC compatible
platform, and the first on that platform to gain widespread use (it was still
widespread more than 10 years later). This was a quick and messy affair
(the variant MS-DOS, sometimes colloquially referred to as Messy DOS,
was developed from QDOS, which literally meant "Quick and Dirty
IBM-PCs were only distributed with PC-DOS, whereas PC compatible
computers from nearly all other manufacturers were distributed with MS-
DOS. For the early years of this operating system family, PC-DOS was
almost identical to MS-DOS. More recently, free versions of DOS such as
FreeDOS and OpenDOS have started to appear.
Early versions of Microsoft Windows were little more than a graphical
shell for DOS, and later versions of Windows were tightly integrated with
MS-DOS. It is also possible to run DOS programs under OS/2 and Linux
using virtual-machine emulators.
Because of the long existence and ubiquity of DOS in the world of the PC-
compatible platform (DOS compatible programs were made well into the
90's), DOS was often considered to be the native operating system of the
PC compatible platform.
Dr. Tracy Bradley Maples (Fall 2005) 2
Microsoft Windows (From Wikipedia, the free encyclopedia.)
The Microsoft Windows family of operating systems originated as a
graphical layer on top of the older MS-DOS environment for the IBM PC.
Modern versions are based on the newer Windows NT core that first took
shape in OS/2. Windows runs on 32- and 64-bit Intel and AMD computers,
although earlier versions also ran on the DEC Alpha, MIPS and PowerPC
architectures (and there was work in progress to make it work also on the
Today, Windows is a popular desktop operating system, enjoying a near-
monopoly of around 85% of the worldwide desktop market share. It is also
widely used on low-end and mid-range servers, supporting applications
such as web servers and database servers.
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Unix (From Wikipedia, the free encyclopedia.)
Unix or UNIX is a computer operating system originally developed in the
1960s and 1970s by a group of AT&T Bell Labs employees including Ken
Thompson, Dennis Ritchie, and Douglas McIlroy. Today's Unix systems
are split into various branches, developed over time by AT&T, several
other commercial vendors, as well as several non-profit organizations.
Unix was designed to be portable, multi-tasking and multi-user. The Unix
systems are characterized by various concepts: plain text files, command
line interpreter, hierarchical file system, treating devices and certain types
of inter-process communication as files, etc. In software engineering, Unix
is mainly noted for its use of the C programming language and for the
The present owner of the UNIX trademark is The Open Group, while the
present claimants on the rights to the UNIX source code are The SCO
Group and Novell. Only systems fully compliant with and certified to the
Single UNIX Specification qualify as "UNIX" (others are called "UNIX
system-like" or Unix-like).
During the late 1970s and early 1980s, Unix's influence in academic
circles led to massive adoption (particularly of the BSD variant,
originating from the University of California, Berkeley) of Unix by
commercial startups, the most notable of which is Sun Microsystems.
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Mac OS (From Wikipedia, the free encyclopedia.)
Mac OS, which stands for Macintosh Operating System, is a range of
graphical user interface-based operating systems developed by Apple
Computer for the Macintosh computers. The original Mac OS is often
credited for popularizing the graphical user interface successfully. It was
first introduced in 1984 with the original Macintosh, the Macintosh 128K.
Apple deliberately played down the existence of the operating system in
the early years of the Macintosh to help make the machine appear more
user-friendly and to distance it from other operating systems such as MS-
DOS, which were portrayed as arcane and technically challenging. Apple
wanted Macintosh to be portrayed as a system "for the rest of us".
Therefore the term "Mac OS" didn't really exist until it was officially used
during the mid-1990s. The term has since been applied to all versions of
the Mac system software prior to this as a handy way to refer to it when
discussing it in context with other operating systems.
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Mac OS X (From Wikipedia, the free encyclopedia.)
Mac OS X brought Unix-style memory management and pre-emptive
multitasking to the Mac platform. It is based on the Mach kernel and the
BSD implementation of UNIX, which were incorporated into NeXTSTEP,
the object-oriented operating system developed by Steve Jobs's NeXT
company. The new memory management system allowed more programs
to run at once and virtually eliminated the possibility of one program
crashing another. It is also the second Macintosh operating system to
include a command line (the first is the now-discontinued A/UX, which
supported classic Mac OS applications on top of a UNIX kernel), although
it is never seen unless the user launches a terminal emulator.
However, since these new features put higher demands on system
resources, Mac OS X only officially supported the PowerPC G3 and newer
processors, and now has even higher requirements (the additional
requirement of built-in FireWire (IEEE 1394), as of Mac OS X v10.4).
Even then, it runs somewhat slowly on older G3 systems for many
Mac OS X includes a compatibility layer for running older Mac
applications, the Classic Environment. This runs a full copy of the older
Mac OS, version 9.1 or later, in a Mac OS X process. Most well-written
"classic" applications function properly under this environment, but
compatibility is only assured if the software was written to be unaware of
the actual hardware, and to interact solely with the operating system. The
Classic Environment will be eliminated in the x86 version of OS X,
Leopard, though it will remain in the Power PC builds of the OS.
Users of the original Mac OS generally upgraded to Mac OS X, but a few
criticized it as being more difficult and less user-friendly than the original
Mac OS, for the lack of certain features that had not been re-implemented
in the new OS, or for being slower on the same hardware (especially older
hardware), or other, sometimes serious incompatibilities with the older OS.
By 2005, it is reported that almost all users of systems capable of running
Mac OS X are so doing, with only a small percentage still running the
classic Mac OS.
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