5.3.1 Software - Operating Systems & user interfaces 

Operating Systems Software: 

The Operating System (OS) of a computer is the complex software that actually controls the input, output and storage devices of the computer, as well as acting as an interface between the user and any other software that is installed.

Examples of systems software:

• Microsoft Windows XP, Microsoft Windows NT, LINUX and UNIX are different operating systems that can be used to control computers.

The following are examples of the functions that an operating system has to be able to do:

• Allocating a processor 'time slot' for each programming task that is running
• Managing the priorities for each programming task that is running
• Allocating and keeping track of the memory used for storing programs and data
• Managing the transfer of data between memory and the backing store
• Handling input operations from the user and from other input devices
• Handling output operations
• Managing the system security

System utility programs work with the operating system. Examples include programs to format floppy disks, copy files etc.

Types of user interface:

Many computer or database operating systems use complex programming languages which are not easy to use.  A user interface is created to allow easier control of the operating system by the user of the system.

A good interface should be easy to use, for example: 

• consistent menu structures;
• consistent operations from actions like clicking the right mouse button.

Examples of user interfaces:

• Command line interface (CLI) - commands are typed directly into the computer and then the enter button is pressed to run them. The commands must be entered correctly and are often abbreviated. They can be difficult to remember.

Example:

c:>copy c:\examplefile.doc a:

This command would copy a file called 'examplefile.doc' from the hard drive (drive C) to a floppy disk (drive A).

• Graphical User Interface (GUI) - This type of interface is sometimes called a WIMP interface (Windows, Icons, Menus, Pointer). The contents of folders (directories) and the output from programs are displayed in rectangular 'windows' which can be moved and resized. Icons (small pictures) are used to represent files or software and the mouse can be used to move the icons, run programs and select options from pull-down menus.
• Features of a good GUI:
  • Items are placed in similar positions on different screens.
  • Navigation between screens is easy and consistent with an escape route available to return to a main screen.
  • Text should be easy to read for all users.
  • Screens should be uncluttered with good use made of colour.

Comparing a Command Line Interface with a Graphical User Interface