Unit 2
Operating Systems

Operating system software - to control and monitor the running of application programs and to allow users to communicate with the computer

Memory management - allocate memory to each application as well as to itself

Resource allocation and scheduling - allocate processing time, memory and input/output resources to programs to make best possible use of computer's resources

Backing store management - controls transfer of data between disk and memory and maintains directory of disk so files can be located quickly

Interrupt - signal to CPU requesting attention

Multiprogramming - more than one program in memory appearing to operate simultaneously

Virtual memory - OS stores only a few pages of each program in memory at any one time so that memory appears to be larger than it is

Virtual machine - OS functions in such a way as to hide from the user all the complexities of the hardware

Batch processing - processing carried out from beginning to end without user interaction

Interactive OS - user and computer in direct two-way communication

Real-time OS

On-line processing - user interacts directly with main computer

Off-line processing - computer devices not under immediate control of main computer

Network OS - controls who logs on to network and access rights etc.

File manager - holds info about each file/folder saved

Drive - hardware that seeks, reads and writes info to and from disk


  1. Normally, making backup which will not be changed
  2. In case of Windows, attribute used by OS to decide which files to backup when

Backup - making copies of data or programs in case the originals are corrupted or lost

Differential backup - copies only those files that have changed since the last normal backup (e.g. every day)

Normal backup - copies all selected files (do e.g. once a week)