GCSE OCR Computer Science - Systems Software

Operating System (OS)

A piece of software that helps to manage a computer system’s resources and provide an interface between the user and the system hardware.

6 Main functions of the CPU

• Memory management and multitasking

• Peripheral management and drivers

• User interface

• Security (User management)

• File management

• Provides a platform for applications to run

Peripheral

External hardware connected to the computer.

Device driver

A piece of software that allows communication between the OS and hardware.

User interface

Allows the user to communicate with a computer system.

Graphical User Interface (GUI)

A type of user interface designed to be more user-friendly, by making them visual and intuitive.

WIMP

Using windows, icons, menus and pointers.

Command-line interface

A text-based user interface for advanced users in which users enter specific commands to complete tasks.

Advantages of command-line interface

• Less resource heavy

• More efficient and powerful

How does an OS manage memory and CPU processing time in order to carry out multitasking?

• Only the necessary parts of an application are moved to memory

• Divides CPU time between applications and may prioritise some over others

• Uses memory buffers to temporarily hold data during transfer

File management

• Data is organised into a hierarchial structure

• Manages the naming, saving, movement, editing and deletion of data.

Single-user OSs

Allow only one user to use the computer at once.

Multi-user OSs

Allow several users to use the computer at the same time.

User management

Different user accounts can be granted access to specific data or resources, and each has their own personal data and desktop.

How does the hard disk become fragmented?

• Small gaps are created as files are moved, deleted and changes size

• The OS splits files up to fill in the gaps

What’s the problem with derfragmentation?

Reading and writing files is slower as the read/write head has to move back and forth.

Defragmentation software

Reorganises data on the hard drive to put fragmented files back together and collect free space.

Why do SSDs not require defragmentation?

• They use flash storage and have no moving parts

• Data can be accessed just as quickly however it’s arranged

Compression software

Reduces file size by permanently or temporarily removing data.

Encryption software

Encrypts data to prevent it being understood if it is intercepted.