An operating system is the program required to interact with the computer hardware. The five main roles of an operating system are process management, memory management, file management, input/output management and interpreting user commands.

Batch operating systems prepare data then process all in one go.

Real time operating systems are constantly updated.

Interactive operating systems respond to user commands.

Multi-access systems allow more than one user to connect to a computer system at one time.

Multi-tasking, also known as multi-programming, is the ability of a computer system to run more than one program at one time.

A hierarchical filing system allows users to group files in folders or directories to allow people to easily navigate and retrieve their files.

The Central Processing Unit is made up of the control unit, the arithmetic and logic unit and registers.

Memory is organised into separate memory locations each with a unique memory address to allow the storage and retrieval of data.

Binary is the language used to represent all forms of data in the computer.

Text is stored using ASCII codes, a unique binary code for each character.

Images consist of pixels. The quality or resolution of an image is measured by the size and density of the pixels. By allocating more memory to each pixel it is possible to increase the colour depth - the number of possible colours for each pixel.

Integers are whole numbers, real numbers are numbers with a decimal fractional part. Real numbers are stored using floating point representation. This method uses a mantissa and an exponent.

A bit is the smallest item of data that a computer can store. 8 bits equals one byte. 1024 bytes equals one kilobyte. 1024 kilobytes equals one megabyte. 1024 megabytes equals one gigabyte. 1024 gigabytes equals one terabyte.