Concentric disk tracks of a hard disk (one on top of the other) form a cylinder.
database management system (DBMS)
A computer-based system for defining, creating, manipulating, controlling, managing and using databases.
The pathway between the memory or peripheral and processing unit that carries data for processing or data that has been processed. See also definitions for "bus" and "address bus".
A method of reducing the size of data. All redundancy in the data is removed to reduce the storage needed or to speed up transfer. The data can be uncompressed back to its original state.
the correctness of data after processing, storage or transmission.
A data type that is a member of a class.
Part of a transmitted message that is sent separately. Apart from containing a portion of the message it will have other data such as check digits, destination address and so on.
Method of ensuring that personal data is correct and is not misused either by those holding it or others who have no right to access it.
Method of ensuring that data is correct, safe and cannot be read or changed by those who have no right to access it.
See the definition for "database management system".
A program used to detect, trace and eliminate errors in computer
An application that reads file segments from non-contiguous sections of a storage device and then writes the files to the same device in such a way that each file segment is contiguous.
De Morgan's law
If A and B are Boolean expressions, then A + B¯ = A¯ . B¯A . B¯ = A¯ + B¯
To remove an item from the front of a queue. See also the definition for "enqueue".
A digital code attached to an electronic message or document, which is unique and which can be used to authenticate the sender or owner. Most often used in electronic commerce.
direct access file
A file organized in such a way that a calculation provides the address (location) of a record so that the record can be accessed directly. The records in the file may be ordered or unordered.
Access to memory and devices without the direct control of the processor. This is most often used for hard disk access and screen display.
RAM set aside to speed up access to a hard drive. This may be part of the disk itself or may be incorporated in cache memory.
A network in which some or all of the processing, storage and control functions, in addition to input/output functions, are dispersed among its nodes.