Operating System

Operating System:
The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

Types of Operating Systems:

Single user systems: A virtual machine with one user at any one time. Generally no provision to share resources. Major emphasis on simple command language or GUI, easy to use file system and standard I/O functionality involving disk/screen/printer.
Operating systems for home & personal computers fall into this category, examples of which would be CPM, MSDOS (Old 8 and 16 bit Operating Systems), Windows 9x, Windows ME, Windows XP, Linux (32 bit Operating Systems)Single user systems in a shared environment: a virtual machine with one main user, sharing resources over a local peer to peer network (a typical small office environment).
Examples: Windows NT, Windows 2000, LinuxThe following large enterprise based systems would probably use stable and scalable operating system such as Unix. Microsoft is attempting to break into this market with Windows 2000 /XP onwards.

Process control: Control by computer of an industrial process. A common feature is the use of feedback. Main features of such an operating system are reliability with a minimum of operator intervention and ‘fail safe’ routines in the event of hardware malfunction.Typical environments would be oil refining or railway signalling.

File Interrogation Systems: Where the computer is used as a database or repository of alarge amount of information about some aspect of the outside world. The user should be able to access the information without any knowledge of the internal organisation (in terms of software structure of hardware storage).

Transaction Processing Systems: Typically indicated by frequent modification of the database (several times per second), as in Banking or Airline control system. Should be able to handle the problems inherent in simultaneous access.

General Purpose Systems: Characterised by a large number of users performing a wide variety of independent tasks. Often classified into batch (no user interaction) or multi-access (user interaction).Distributed Systems: Interconnected computers sharing files, sending messages and sharing tasks.
Advantages: equalises the load of a system and allows programs to be executed on other machines more suitable to the task.Modern Operating System design increasingly incorporates complex communication methods to deal with the communications between computers and co-operating machines.

Common features of Operating SystemsConcurrency: Several processors and I/O devices in operation at the same time Sharing of resources: Sharing the processor(s), Store/Memory, I/O devices, programs Long term storage: Typically on disks Non-determinacy: Must be able to respond to events occurring in an unpredictable order in a consistent, error - free way.

OPERATING SYSTEM TYPES:As computers have progressed and developed so have the types of operating systems. Below is a basic list of the different types of operating systems and a few examples of Operating Systems that fall into each of the ategories. Many computer Operating Systems will fall into more then one of the below categories:
*GUI - Short for Graphical User Interface a GUI Operating System contains graphics and icons and is commonly navigated using by using a computer mouse. Below are some examples of GUI Operating Systems.System 7.x,Windows 98,Windows CE.
*Multi-user - A multi-user Operating System allows for multiple users to use the same computer at the same time and/or different times. Below are some examples of multi-user Operating Systems.Linux,UNIX,Windows 2000.
*Multiprocessing - An Operating System capable of supporting and utilizing more than one computer processor. Below are some examples of multiprocessingOperating Systems. Linux,UNIX,Windows 2000.
*Multitasking - An Operating systems that is capable of allowing multiple software processes to be run at the same time. Below are some examples of multitasking Operating Systems. UNIX,Windows 2000.
*Multithreading - Operating systems that allow different parts of a software program to run concurrently. Operating systems that would fall into this category are. Linux,UNIX,Windows 2000.
*Operating SystemsDOS , Linux, Windows (windows *9x, windows 2000 server windows ME and windows XP)Unix , OS/2,Mac,Netware, NT ,VMXDOS: (Disk Operating System) was developed by Microsoft. IBM also has its own version. It is a single tasking O/S, command line oriented and not user friendly. It is now been discontinued after version 6.22.
Windows:Windows is today the most popular O/S for businesses and home PCs particularly. This is because it is very user friendly, easy to use and has encouraged numerous people to use the computer. It allows you to do more than one thing at a time and has a stylish and easy to use GUI (graphical user interface). It even makes it easy for PCs not running its network versions to easily share resources in a peer-to-peer manner.
Windows has several flavours including:
Windows 3.0 – 1st version of windows, highly dependent on DOS for its O/S functionality
Windows 3.11- same as 3.0 but built with workgroup networks in mind
Windows 95 – very first window full O/S
Windows 98 – in improved version of Windows 95 with more utilities.
Windows millennium edition – home and multimedia version of win98 with even more utilities
Windows 2000 professional – a stable and security conscious version designed for professional use.
Windows 2000 server – a network version of windows 2000 with support for more file systems.
Windows data centre – a massive version of windows 2000 serverWindows XP – the latest version of windows.
Windows NT - the 1st network version of windows with support for up to 256 users per NT server. NT is an acronym for new technology.
Linux: a Unix based O/S best described as the G.U.I. version of Unix. It is more users friendly than it parent O/S and employs HCI’s metaphors a greater deal. Like windows it allows you to perform more than one task at a time.
Unix: an advanced O/S more suitable for network use. Unix is popular among large organisations particularly those with I.T. background. It is the best multi-user, multitasking O/S with extensive stability. Most web servers still utilises Unix. It has support for a wide range of software. Unfortunately it works like DOS being command line based.
O/S 2: This is IBM’s O/S in the late 70’s. It is similar to DOS but was discontinued rather quickly.
Mac: The Mac O/S is only used in Macintosh computers. It is user friendly with support for high graphics handling. It is also suitable for multitasking. Mac is now up to V08 O/S.
Netware: this is NOVEL’s popular network operating system with early support for dedicated and non-dedicated servers. Netware is a very security conscious NOS (Network Operating System) and administrative functions. It is fairly user friendly and way between Windows NT and Unix.
VMX: is an older O/S only popularly with organisations that use mainframe computers.