The main functions of an operating system

The Main Functions Of An Operating System

Here I am going to explain the main functions of an operating system

Processor management

The operating system must assign enough cycles to each process to get the job done and must give each process enough time with the CPU to function properly. (CANT MAKE IT NOT SOUND LIKE THE FUCKING SITE! STUPID EFFICIENT SITE)On a single tasking system it only needs to pause to deal with user input and certain interrupts. On a multitasking system the system must priorities each process switching between them thousands of time per second in order for it to give the appearance that things are happening at once. On multi-core and multi-processing systems, processes on each core may be running at the same time as the other core but each processor core can only hanlde one task at a time.

Memory management and storage.

The operating system must also ensure that memory doesnt clash with other memory and that each process is given enough memory to execute. For this to happen the operating system must assign memory boubndaries for types of software and individual applications.  Applications are loaded into memory in block of a certain size assigned by the operating system. Every process will be given a multiple of that number in size so that memory will not overlap if there it is micalculated bit.

Tthe operating system must make sure that all the different type of memory are used in an efficient way. This includes ROM, RAM, cache memory, virtual memory and hardisk space.

For instance when RAM is full some of the processes not being used can be saved onto the hardisks and recalled when it is needed. It can keep procceses that are used frequently into high speed cache memory so that it can be retrieved quicker rather than being read from RAM evertime.

Device management

This is the management of all the input and output devices such as keyboards and printers. For instance if there is to much data coming in from the keyboard for the cpu to handle the operating system can instruct a buffer to keep taking information but to stop sending it to the cpu. DO I NEED TO EXPLAIN WHAT DRIVERS ARE?

User interface

There are many difference type of user interface but all do the same task which is to be the translator between machine code and the user. It allows for the user to communicate with the machine and for the machine to output the effects of the users actions.

Main types of Operating System

A comparison of the four main types of operating system. – The Personal computer, Network Computer, Mainframe and Mobile Phone/PDA.

Main Differences

A mainframe is designed to input process, move around and ouput large amounts of date fast and efficeintly. It is the most reliable, stable, and secure of all. Looks wise quite large (get better description)

A PDA is designed to be small. They use simpler instructions which take up less memory are  therefore more limited to the sort of thing they can do and run.

Network – is like a PC but It uses less storage, less memory and does less processing.  It is a little like a computer which mostly deals with input and output the rest is done elsewhere on a server.

A PC is gerneral purpose meaning can do a wide range of different tasks.

User interface

Mainframes didn’t used to have user interfaces only accepting input via punch cards and tapes etc. Now they support GUI like the others.

All use GUi but recent phones/PDA’s come with touchscreen which is an interactive from of GUI ehich accepts input.

Users can access a mainframe either by a computer terminal but theser days most can go online via a personal computer and acces the mainframe via a personal computer.

device management

The mainframe use many subsidury computers to hanlde I/O devices. unlike the other 3 who devices connect directly to the main unit.

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You can connect a wide range of devices to a PC or network computer such as printers and scanners unlike the PDA where you are limited to headphones usb and sometime a keyboard. You cannot add more and detract from like you can with a PC which uses special drivers to be able to communicate with the operating system.

Memory Storage Management

A Mainframe can have multiple hardrives therefore store extremly high volumes of data unlike a pc which usually only has one. PDAs on the other hand do not have a hardisk but use rom to store the operating system and pre-installed programs such as the claender and phonebook. If you add programs these are stored in RAM. You do not loose this data when the phone is turned of because the phone is run on batteries which still have a small bit of power left in them when the phone is turned off. Network computers also often don’t have a hardisk using the network to store and access data and run programs.

Processor Management

pc’s pda’s and network computers are all single user operating systems unlike mainframes which use multi user operating systems.

Unlike PDA’s and network computers mainframes can run multiple operating systems. modern pc’s can also do this in the way of a virtual machine but not to the extent and sophistication of a mainframe. Unlike the other three mainframes use multiple processors and can share their workload between them. Whereas network computers are able to use the the server for some of their processing.

change sophistication so it isnt copying

Unlike the others mainframes use single tasking operating systems

Well Known – Operating Systems

A Comparison between MS Windows, MS-Dos, Linux and Mac-OS.


Introduction to MS-DOS

MS DOS Stands for Microsoft Disk Operating System. IBM released the first ever personal computer in 1982 which came with MS-DOS. MS-DOS is a re-named version of Q-DOS (Quick and Dirty Operating System) which was owned by Seattle computer Products at the time. Soon after the release of MS-DOS Microsoft bought the licensing rights from Seattle computers.

MS-DOS was then Liscenced by around 50 companies in 1982 and was used on most personal computers throughout the 1980’s.Like windows and Mac, MS-DOS was closed source. Closed source means that you are unable to see the source therefore unable to change or make any additions to the operating system via the source code. Therefore the only person who would be able to provide updates or newer versions would have been Microsoft themselves.


It uses a command line interface rather than the modern Graphical User Interface (GUI) that we see on personal computers now.

  • This means that they were not yet “user friendly.” For this reason MS-DOS would have been used by skilled workers rather than the general public for personal use.
  • MS-DOS was a Single Tasking operating system and with the lack of GUI was suited and used for jobs such asfile management, simple networking and batch processing.
  • Single tasking also means that it would run more efficiently i.e. quicker for certain tasks
  • MS-DOS memory management would have differed to that of more recent computers as there would have been no high speed cache memory or virtual memory and there would have been no need for this on a single tasking system.
  • Because MS-DOS is this basic it does not take up as much storage space and doesn’t use as much RAM to run.

Where MS-DOS is now

  • MS-DOS was gradually replaced by MS Windows with the invention of GUI and windowsAPI (Application Programming Iinterface.) It was eventually discontinued in 2000.
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  • MS-DOS is now used as a standalone product but is now used for bootstrapping and troubleshooting.

MS Windows

Introduction to MS-WINDOWS

  • Microsoft windows was developed by Microsoft following on from MS-DOS. The first version of MS-Windows realeased in 1985 was not a complete operating system. It was an extension of MS-DOS which provided a graphical user interface.
  • MS-Windows is universal meaing it runs on most computer platforms such as personal computers, workstations, mobile phones/pda’s, tablet pc’s, laptops, media centers, and embedded systems.
  • MS Windows is the most used of current operating systems and can be found in schools, offices and homes across the country.
  • Windows version 2.1 was the first to be given the ability to do such thing as multi tasking. The amount and efficiency of which has been improving ever since.
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Later Versions of windows no longer had MS-DOS underlying and became a modern operating system rather than being considered just the GUI.

Liscencing and cost

  • Unlike Linux, Microsoft usually comes pre-installed and is a fully licensed product. This can be a good thing as you have full technical support when things go wrong but are however restricted to one machine per licence.
  • Windows can cost alot less than mac to purchase however some people argue that cost of maintenance for a windows operating systems makes up for this. Windows is said to be less stable due its software components being connected.


As windows is the most used operating system taking up (90 somehing) percent of the market it is more susceptible to hacking and is therefore less secure than mac and linux. It also means there there is a greater range of 3rd  party software  for windows.


  • Like MS-DOS, Windows is closed source so there is less flexibility in what you can change therefore the GUI is less configurable than linux. However for the same reason it is alot more user friendly.
  • Windows is backwards compatible meaning that softeware made for older versions of windows can also run on newer versions.
  • Windows like most modern operating systems is multi tasking and multi processing meaning it can give the appearance of doing many things at once. This can have its disadvantages in such areas as speed.
  • Even though windows no longer has MS-DOS underlying you are able to bring up the DOS-prompt which has a limited capability unlike Linux where you can run the whole thing in the commandline layer.
  • With all the advancesof windows can now take up to1gb of space as apposed to the low storage that MS-DOS would have taken up.


Introduction to Linux

  • In 1984 Richard Stallman made a free version of unix which he called GNU. Shortly after he wrote the GNU GPL (general public liscence) . His aim was to make software that was freely available to general public.  In 1994 Linus Torvalds released Linux kernel which could be integrated with the GNU system to create a completely free operating system. The name linux is linus’s name combined with Minix which is a simplified version of unix he had based his kernel on.
  • Excerpt from Unix System Security Tools by Seth T. Ross
  • do i use the excert bit or the internet site?

Licenscing and Cost

  • The main difference between Linux the other 3 operating systems is that it is open source and is licenced under the GNU GPL which means it is free and that any one can view it edit it and redistribute it as long as it complies with the GNU GPL Licence.
  • As Linux is not a corporate product and is in many different states/versions it does not have the support that you would get with mac and windows and also doesnt often come pre-installed. It does however have many forums and tech based help on the internet.


  • The advantages of its open source code is that it is free and also if you are very knowledgeable of programming you can control almost everything about the operating system making it a great choice if you want to manipulate it for specific tasks.
  • Unfortunately this detracts from the user friendliness . This problem has been tackled by a failry new version called abuntu meaning () although not quite the userfreindliness that mac and windows demonstrate.
  • This being said Linux’s main user group would be people of a very computer knowleagable background mosrt commonly nicknamed “compuer nerds”.

  • Like Windows linux can be run on a wide range of systems including persoonal computers, desktops, mobile phones/pdassupercomputers, laptops and is welll know fo its use on servers. 
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  • Secuity wise Linux is considered to be the more secure than windows as it is based on Unix (an operating system considered to be very secure) but as stated by John Lettice at “there’s also a reasonable amount of support for the view that Linux would get just as many security issues if it had anything like Windows’ user base.”



  • Mac OS was created by Apple. Mac OS was designed for apple macintosh computers and only runs on Apple hardware.
  • Mac OS does not have a command line interface at all and unlike windows deleting a file will not break the entire system. (ASK BEN IS THIS TRUE?) For this and other reasons it is much more user friendly but anyone wanting to explore or troubleshoot will not be able to.
  • All you see is the GUI so it is therefor the least flexible in its ablity for customization and control over how it works. This is  “”
  • Like windows mac is closed source and  has full technical support


  • Originally I thought that mac was the more expensive of the four but according to Jon Henshaw, M.A. at
  • “Windows and Mac computers are now almost equal in cost. Whereas you can buy a Windows based PC for less than $500, you will not get the multimedia hardware and software that you will want and need. In fact, to do so would cost equal or more to the cost of a Mac.”
  • You also have to consider that there will be less maintenance costs than that of windows.UI


  • Mac is considered more secure than windows which is partly down to it being based on unix but is also as i said previously because windows is more widely used.
  • It is also considered to be more stable which again couldbe down to it being based on unix. According to Jon Henshaw, M.A. at mac doesnt marry its software components together like windows does so when something goes wrong it doesnt all follow suit meaning the whole thing is less likely to crash like windows can often do.45

Type of use/Who uses it?

  • Mac OS is not as widely used as windows and therefore has a smaller amount of software that will run on it.
  • According to “”>Manali Oak at  “While Windows focuses on office function, Macintosh is focused on graphics and multimedia functions.” (“”>
  • This would imply that people who use macs are genraly people who have jobs where they have to use alot of multimedia.


  • If I was going to recommend an OS for someone who is new to computers and didn’t want to know anything about whats going on in the background I would suggest the Mac because of its userfreindly design and also if they mainly iused computers for photos music and videos. I would suggest windows tto someone who wants a large amount of software options and games and who likes to have some ability probe further than (cant finnish the fucking sentence) For those who enjoy or need a completely customisable operating system. If they were not already knowledgeable in programming/command line they would also have to be willing to take on the learning curve. Overal I feel the Mac will be the operating system of the future assuming that there is a larger software base and that it becomes more affordable. 100 ALSO WRITE ABOUT WINDOWS AND LINUX BEIGN THE CHEAPER OPTION IF MAC IS TO EXPENSIVE?



1.2 Glossary

1.2.1 Proprietary

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