1 3 Computing System Fundamentals 3.3 Computer Systems

3.3.1 Operating Systems

3 System software Programs that (often without the user’s knowledge) handle the background tasks required on a computer for its effective functioning. As opposed to application software, which is installed and run by the user for a specific purpose. System software = operating system + utility software.

4 System software The operating system (OS) is the system of programs that co-ordinates the interactions between the hardware, other software and the user Utility software provides tools for system maintenance and repair and are not necessarily part of the OS e.g. anti-virus software.

5 OS functions communicating with peripherals, co-ordinating concurrent processing of jobs, memory management, resource monitoring and accounting, security, program and data management, network management and providing appropriate user interfaces.

6 Peripheral communications Peripherals include monitors, printers, disk drives, etc. Most of these will require programs called drivers to allow communication. Sometimes these drivers need to be installed into the OS separately.

7 Concurrent processing A single processor apparently multi-tasks by switching rapidly between different jobs. The OS co-ordinates this by taking advantage of pauses in one process (e.g. waiting for input) to perform another.

8 Memory management With several tasks running concurrently, the OS avoids errors by protecting each task’s memory area and allocating space as required. This may involve the use of virtual memory on the hard drive.

9 Resource monitoring The OS keeps a log of available resources connected to the system. This helps with accounting, since on some systems users are charged for the time and resources they use (e.g. for printing).

10 Security Most OS’s require a log on (use of a user ID and password). This allows: ‣ recording of user activity, ‣ restriction of resources to only those with relevant permissions

11 Program/data management The OS acts as a librarian, accessing and loading files requested by the user and by other programs. This requires the use of an organised file system, with a way of representing a folder structure.

12 Network management Modern OS’s are all networkable. Data within the computer must be made compatible and transmitted according to standard network protocols. The OS must be able to recognise and filter data according to their purpose and intended destination.

13 User interface The way that the computer presents itself to the user. There are three broad types: ‣ Command-line ‣ Menu-driven ‣ Graphical User Interface (GUI)