Computer Architecture Definitions

Memory Location

A seperately addressable area of main memory

RAM

Random Access Memory; volatile main memory on which the locations can be accessed directly in any order with the same access time for all writing and reading operations.

ROM

Read-Only Memory; non-volatile main memory that cannot be written to once it is set up.

EEPROM

Electrically Erasable Programmable read-only memory; its contents may be altered but writing is 100 times slower than reading.

Computer Bus

A set of parallel wires connecting independent components of a computer system.

System Bus / External Bus

The main highway connecting the processor, main memory and I/O controllers; it is made up of a data bus, an address bus and a control bus.

I/O

Allows the CPU to communicate with the peripherals.

Peripheral

A computer device that is not part of the CPU. It can be external (eg. mouse, keyboard, printer etc.) or internal, such as a CD-ROM drive.

I/O Device

A hardware unit that sends or recieves data or stores data by communicating with the processor and main memory through an I/O controller.

Secondary Storage

Permanent storage memory not directly connected to the processor; also called backing store.

Main Memory Address

A unique numeric code corresponding to a location in memory.

Stored program concept

A program must be resident in memory to be executed; it is processed by by fetching machine code intructions in sequence from main memory and executing them, one at a time, in the processor.

Register

A very fast memory location inside the processor or I/O controller.

General Purpose Register

A register not assigned a specific role by the processor designer. Programmers may use these.

Dedicated Register

A register assigned a specific role by the processor designer. Programmers may use some but not all dedicated registers.

Clock speed

Of a processor; the frequency or megahertz/gigahertz at which the processor executes instructions.

Word Length

The number of digits in a binary word.

Bus Width

The number of signal wires or lines allocated to the bus.

Hardware

Electrical circuits that a computer is assembled form. The platform on which the software executes.

Main Memory

Memory that is directly addressable by the processor.