Functions of an operating system

Operating Systems



Explain what is meant by an 'operating system'

• The operating system is a software necessary to run all computing devices. It deals with controlling all aspects of the computer e.g. controls and organises the general operation of the copmuter. The OS makes it easier to write applications. It sits betweeen applications and hardware on the computer.
• Kernel is the lowest level of OS and controls the hardware

When is the operating system loaded?

• The operating system is part of the computer booting and loading up. when you turn the computer on the operating system must be loaded from the Hard Disk into RAM befrore the computer can be used.

List some commonly used operating systems:

Operating system	Use
Windows		Personal computers
Linux		Personal computers
MacOS		Macs
UNIX		Mainframes
Symbian, Androids		Mobile phones

Explain how the operating system controls the software and hardware on the computer

• The operating system manages communications between software and hardware. For example: 

                 - Loading and saving data and programs

                 - Communicating with peripherals such as a mouse or a printer

                 - Organizing data stored on a hard disk

                 - Displaying information on the VDUMessages are sent to and from the operating system where the task is read and performed by the operating system

Describe two types of user interfaces provided by the operating system

• Graphic User Interface (GUI) - icons that load your programs that show up on your desktop, colours that set the background colour
interacts with computer using a pointing device (e.g. mouse or trackball). Most popular form is a Windows, Icon, Menu and Pointer (WIMP) system. The features  include:

Window : An area of the screen which is used to display a particular program or piece of work. Many windows can be displayed on the screen at the same time. e.g.

Icon : An informative picture / symbol displayed on the screen which the user chooses to select an action. Icons can usually be used to represent software packages, documents and hardware devices. e.g.

Menu : A list of options which the user can pick from. Menus can be pull-down (selected from a menu bar at the top of the screen) or pop-up (selected by pressing a mouse button). e.g.

Pointer : A symbol such as an arrow which is moved by a pointing device and can be used to select objects.

Advantages

Disadvantages

Most operations are self-explanatory so that you do not have to remember lots of commands. Some operations are much easier using a GUI with a pointer. e.g. selecting text or drawing pictures. Often you can have more than one program running at the same time, each of them using different windows. Often GUIs are WYSIWYG. What you see on the screen is what you get if you do a printout. Often with a GUI many programs use a similar interface, so it is easier to learn how to use a new program. Most GUIs provide good help facilities.

GUIs can take up a lot of memory and need to be run on a fast computer. If you have a slow computer, a GUI may work slowly or not at all.

• Command User Line Interface (CUL) - interaction with a computer using a command line interface usually follows these two steps :
  • The user types a command e.g. "dir".
  • The computer carries out the command and displays its results.

Advantages	Disadvantages
An experienced user who knows a package well can enter commands quicker than he could select options using lots of menus. Can be used on a computer which has very little memory and is slow.	It is very difficult to remember all the possible commands and exactly how they should be typed. Error messages are not usually very helpful.

Explain what is meant by a 'multitasking operating system'


A multitasking operating system is allowing the computer to perform more than one task/program at once.


Explain the difference between client and server operating systems

• Client Operating Systems - optimized to do everyday tasks like word processing, internet browsing
• Server Operating Systems - highly customized and optimized for hosting demanding applications