Operating Systems

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Operating system: software that manages a computer system

Loaded by the bootstrap loader.

Primary functions:

Managing resources

Providing a user interface

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Managing resources

Manages peripherals such as input and output devices

Communicates with and sends data output to an output device

Communicates with and receives data input to an input device

Manages printing using spooling

Data is stored on hard disc/in memory/in a queue

Document is printed when printer is free

User can carry on working/log off while waiting for job to print

Manages backing store

Ensures that data is stored and can be retrieved correctly from any disk drive

Creates and maintains filing systems

Organizes files in a hierarchical directory structure

File compression

The amount of data is reduced and the file is made smaller

Compression is used to save disk space

Disk de-fragmentation

Fragmented files are split up and stored on different parts of the disk

Disk fragmentation will slow down disk access speed

Disk de-fragmentation is when file parts are physically re-arranged into the order required for access

Manages memory (RAM)

Ensures that programs/data do not corrupt each other

Ensures that all programs and data including itself is stored in correct memory locations

Manages processes

Ensures that different processes can utilize the CPU and do not interfere with each other or crash

On a multitasking OS ensure that all tasks appear to run simultaneously

Manages security

Allows creation and deletion of user accounts

Allows users to log on and change passwords

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Providing a user interface

Allows copying/deleting etc. of files or folders

Allows access to system settings such as hardware

Provides a command line interface

Allows users to have more than one window open

Provides a graphical user interface

Provides users with errors/help messages

Allows customization of interface

Allows user to switch between tasks