OCR Computing A-Level Revision


This glossary contains all the key terms and definitions you need to learn by heart.

Applications Software - software which helps the user complete specific tasks - for example word processing.

Archive - information is archived if it doesn't need to be accessed frequently, but it may need to be accessed at some point in the future. For example student records after students have left the school - if the student later asks for a reference, then the school would have to retrieve their student record from the archive.

Basic Input Output System (BIOS) - where important instructions explaining how to turn on the computer are stored - for example, how to find a keyboard and interpret keystrokes.

Bit - a binary 1 or 0. Bits are normally part of a byte.

Bitrate - the amount of data (measured in bits) that can be transmitted per second. Can also be called the baud rate.

Byte - a group of bits (usually 8) treated as one unit.

Checksum - an extra byte that is added to a block of data, which is the sum of the bits, ignoring any carry. This is then calculated by the receiver, and if the checksums match, then the data is accepted.

Duplex - where data can travel in both direction at the same time - e.g. ethernet.

Echo (Error Checking) - when data is sent, a copy is then returned to the sender, to check it is the same data as the sender sent.

Error (Data Transmission) - where data is corrupted (changed) while being transferred from one place to another. See 1.5.4 Error Checking.

Ethernet - a cable standard used to connect nodes within a LAN.

Graphical User Interface (GUI) - an intuitive interface using images to represent commands. It is easy for beginners to use, however it can be slow as many commands are hidden so the user is not confused.

Half Duplex - where data can travel in both directions, but only in one direction at a time - e.g. a walkie-talkie.

Handshake - before two devices can communicate, they must ensure they are both ready to communicate, and agree the protocols to be used, by completing a "handshake".

Hardware - the physical components which make up the computer. Hardware hurts if you are hit over the head with it.

Input Device - a type of peripheral that can accept data, decode it, and send it as electrical pulses to the computer. For example: keyboards, mice, digital cameras, and microphones.

I/O Device - a device that communicates between the computer and the outside word - for example a keyboard or a printer. Sometimes also known as an HID (Human Interface Device).

Local Area Network (LAN) - computers connected to each other in a geographically small area, for example a home network.

Magnetic Ink Character Reader (MICR) - reads characters which have been printed using special magnetic ink. The only common use for MICR is the account information printed on the bottom of cheques. Unlike barcodes, MICR can easily be read by both humans and computers.

Network - 2 or more computing devices connected together so that they can share data and resources.

Network Interface Card (NIC) - an expansion card that allows a computer to connect to a network. Most motherboards have wired (ethernet) NIC's built in, but an expansion card might be required for wireless access.

Node - a piece of equipment, such as a PC or peripheral, attached to a network.

Optical Character Recognition (OCR) - converts text on paper to digital characters, by comparing a scanned character with a database. Works best on typed pages, but also works with handwriting.

Optical Mark Reader (OMR) - recognizes marks on a sheet of paper. Commonly used in multiple choice exams, or on lottery tickets.

Output Device - a device that turns computer signals into a human-readable form, like a screen, printer, or speaker.

Packet - a group of bytes for network transmission. Each packet has a unique ID (a label), a sequence number, a destination address, and a checksum.

Parallel (Data Transmission) - using many wires, each transferring a bit at the same time (e.g. 8 wires to transfer an entire byte of 8 bits).

Parity Checking - a method used for error checking, where it is agreed that the number of bits will be odd or even. 7 bits of the byte are used for actual data, and one of the bits is used to ensure the parity is correct. See 1.5.4 Error Checking.

Peripheral - a device that is connected to a host computer, but not part of it. For example, a webcam or a graphics card would be a peripheral, as they are not required for a computer to operate. However, a power supply would not be a peripheral, as a computer would not function without one. Although RAM is technically a peripheral, removing it will effectively disable any modern machine, therefore it is a primary component.

Primary Component - a piece of hardware which is critical for a computer to work. For example, a CPU, or a power supply.

Primary Memory - ROM and RAM.

Protocol - a set of rules governing the transmission of data. There are two types of protocol - logical protocols (relating to software) and physical protocols (relating to hardware).

Random Access Memory (RAM) - used to store short term information - e.g. when browsing the internet, web pages might be downloaded and stored in RAM. It's name is derived from the fact that random storage locations can all be accessed quickly (less than 1ms) - in contrast to traditional hard disks, which can take up to 10 milliseconds due to mechanical limitations. RAM is volatile memory, so it can only be used for short term storage.

Read Only Memory (ROM) - used to store data that should never be altered, for example the BIOS or UEFI. Information stored in ROM cannot be altered, deleted, or otherwise interfered with.

Serial (Data Transmission) - where each of the 8 bits is transmitted down a single wire connection one at a time.

Simplex - data is only ever able to travel in one direction - e.g. from a radio station to a radio.

Software - the instructions and code that tells the computer what to do. There are two types of software, applications software and system software.

Static State Drive (SSD) - a replacement for hard drives. An SSD is smaller and faster than a hard drive which costs the same amount. Typically, the operating system is stored on an SSD, while large files such as photos, music, and videos, are stored on a "traditional" spinning hard disk.

Standalone - a computer which is not connected to other computers.

Storage Device - a memory device used to store operating systems, programs, and user data. Storage devices are non-volatile - they do not lose their data when they are unpowered. See 1.4.3 Memory and Storage.

Syntax - the particular rules of a given programming language. For example, surrounding strings in quotes (either single or double quotes) is a syntax rule for python.

System Software - system software provides basic functionality, such as file management, or providing a Graphical User Interface.

Unified Extensible Firmware Interface (UEFI) - a modern replacement for BIOS, which will reduce the time it takes for computers to start up. This is because it can be accessed through operating systems, such as Microsoft Windows. It also supports "modern" features, such as a mouse, making it more user-friendly.

Volatile Memory - memory which gets lost when the power is turned off.

Wide Area Network (WAN) - computers connected to each other over a geographically large area, for example the internet.