National Teaching and Learning Change ProgrammeInformation and Communication Technology:
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• radio button
  A menu where a choice is made by clicking a button. Only one choice can be made at any one time.
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• random
  Something chosen by chance.
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• random access memory (RAM)
  Memory that has the same access time for all locations. RAM may be either static, which holds its memory so long as there is a power supply, or dynamic, which has to be refreshed by reading and rewriting the contents very frequently (about every two milliseconds). Dynamic RAM (DRAM) is more widely used than static RAM because it needs less power. Both dynamic and static RAM are volatile, i.e. the contents of it disappear when the power is switched off (hence the need for backing store in a computer).
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• range check
  A type of validation check used when inputting data which would signal any data items outside a plausible range, e.g. a worker
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• raster graphics
  A method of producing an image on a display screen. The image is drawn as horizontal lines of dots, repeated for each line of the screen. The bitmap is encoded as a one-dimensional stream of bits, formed by each line of the display in order. Each pixel in the image may consist of several dots depending on the resolution of the image and the resolution of the monitor, see above. In general any line which is neither vertical nor horizontal will have a jagged appearance. If very high quality screen display of line drawings is required, then vector graphics is the appropriate system.
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• raw data
  Data which has been input into a computer, before any validation or processing.
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• read
  To read a file is to access the data in it.
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• read-only
  A read-only file is one which users can view the contents, but not change or delete them.
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• read-only memory (ROM)
  Memory for which the contents may be read but cannot be written to by the computer system. Read-only memory is used for both data and programs. There are optical ROM systems (e.g. CD-ROM), and semiconductor (integrated circuit) ROM systems. The term ROM is frequently used to mean the (integrated circuit) read-only memory used to hold programs and associated data for building into computers. Software in ROM is fixed during manufacture, but there are other ways of putting programs and data into ROM.
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• read/write head
  The part of a disk drive or tape drive which writes to and reads from the disk or tape.
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• ready
  When a peripheral is ready to receive data, for example when a printer is online and not busy.
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• real numbers
  Numbers which include a fractional part, for example 5.76, 34.835.
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• real type
  Numbers which include a fractional part, e.g. 5.76, 34.98, etc. Also called float.
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• real-time
  A system which responds immediately to an external event, rather than processing being delayed. This is essential in applications such as, for example, air traffic control.
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• reboot
  To reboot the computer is to restart the system, usually after it has hung (stopped working). All parameters will be reset to their initial values and data which was not saved will be lost.
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• record
  Some multimedia software has the option to record video and audio and save this as digital files.
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• record
  A data file consists of a series of records. A record is a collection of items, or fields, which may be of different data types, all relating to the object the record represents. For example, a payroll database would have information about all the employees. The record would be employee; the fields within it would be name, national insurance number, date of birth, wage rate, etc.
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• record format
  The contents of a record are described by the record format which specifies the record in terms of its fields, for example, field type, field length, field name.
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• record number
  A unique number which identifies the position of a record in a file. This means that record no.1 identifies the first physical position and the data in that position. Record numbers are not used in some file structures such as random files.
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• recover
  To recover a file is to get back the original, e.g. if it has been corrupted in some way.