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Thursday, April 4, 2013

What is an Operating System?

- A collection of small and large software that help in the management of the computer hardware resources is called an operating system. 
- As the term suggests it operates or drives the system. 
- The basic common services required by the computer programs are offered by this OS only. 
- Without an OS, the application programs would fail to function. 
- Operating systems are of many types. 
- One such type is the time sharing OS that schedules the tasks to be done so that the processor time, printing, mass storage and so on resources could be utilized efficiently. 
- It is an intermediate thing between the hardware and the user. 
- It is through the OS that you are able to actually communicate with the computer hardware. 
- Functions such as memory allocation and basic input output operations are dependent totally on the OS. 
- Even though the hardware directly executes the application code, it does frequently involve the OS or OS itself interrupts in between. 
- Any device containing a computer do has an OS such as video game consoles, mobile phones, web servers, super computers and so on.
- Some popular OS are:
Ø  Android
Ø  Linux
Ø  iOS
Ø  Microsoft windows
Ø  Windows phone
Ø  Mac OS X
Ø  IBM z/ OS
All the OS have relation with UNIX save windows and z/OS.

- Types of Operating systems are:
  1. Real time OS
  2. Multi – user OS
  3. Multi – tasking OS
  4. Single  - tasking OS
  5. Distributed OS
  6. Embedded OS
- It was in 1950 that the basic operating systems came in to existence such as parallel processing, interrupts and run time libraries.
- Assembly language was used for writing the UNIX OS. 
- There are many sub–categories in the Unix like family of the operating systems:
  1. System V
  2. BSD
  3. Linux and so on.
- A number of computer architectures are supported by these Unix – like systems. 
- They come in heavy use in the following fields:
  1. Servers in business
  2. Work stations in academic
  3. Engineering environments
- Few UNIX variants are available for free such as BSD, Linux etc. and are quite popular. 
- The holder of the Unix trademark is the open group and it has certified four Oss as Unix so far. 
- Two of the original system V Unix descendants are IBM’s AIX and HP’s HP – UX and they run only on the hardware provided by their manufacturer. 
Opposite to these is the sun microsystem’s Solaris OS that can be used on different hardware types (inclusive of the Sparc and x86 servers etc. and PCs). - The POSIX standard was established to the sought the inter-operability of the Unix. 
- This standard is applicable for any OS now, even though originally it was developed especially for the variants of Unix.
- Berkeley Software Distribution or BSD family is a Unix sub–group. 
- It includes the following:
  1. FreeBSD
  2. NetBSD
  3. OpenBSD
- The major use of all of these is in the web servers. 
- Furthermore, they are also capable of functioning as a PC OS. 
- BSD has made a great contribution in the existence of the internet. 
- Most of the protocols were refined and implemented in BSD. 

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