AQA Computer Science Subject-Specific vocabulary

• Absolute Error


  The difference between the actual number and the nearest representable value.
• Abstract data type (ADT)


  A data type whose properties are specified independently of any particular programming language.
• Abstraction


  Representation that is arrived at by removing unnecessary details.
• Aggregation


  A type of association where the aggregated object has a weaker form of association with the objects that it is aggregating than is the case with composition. These objects have an existence independent of the aggregated object and can continue to exist even after the aggregated object is disposed of.
• Ajax


  Web technology that allows only the part of a web page that needs updating to be fetched from the web server.
• Algorithm


  A sequence of unambiguous instructions for solving a problem. It can be represented as a Turing machine program.
• Application programming interface (API)


  A layer of software that allows application programs to call on the services of the operating system.
• Association

  An association is a relationship between two classes. There are different types of association: composition and aggregation.
• Asymptotic behaviour of f

  Behaviour of the function f(n) for very large values of n.
• Asynchronous serial data transmission


  Transmission system in which the sender and receiver have separate clocks which are not kept synchronised. Instead, the clocks are synchronised temporarily at the start of a transmission. The arrival of data cannot be predicted by the receiver; s a start bit is used to signal the arrival of data and to synchronise the transmitter and receiver temporarily.
• Attribute


  A property or characteristic of an entity (databases) or an object (OOP).
• Automation


  Turning an abstraction into a form that can be processed by a computer.
• Backus-Naur Form (BNF)


  A notation technique used to formally describe the syntax of programming languages and other formal languages.
• Bandwidth


  For a transmission medium, the range of signal frequencies it may transmit.
• Base case


  A value that has a solution which does not involve any reference to the general case solution.
• Baseband system


  A system that uses a single data channel system in which the whole bandwidth of the transmission medium is dedicated to one data channel at a time.
• Basic operation


  The operation which contributes most to the total running time.
• Baud rate


  The rate at which signals on a wire may change.
• Behaviours


  The functions of the object or what the object does.
• Bit rate


  The number of bits transmitted per second.
• Broadband

  A multiple data channel system in which the bandwidth of the transmission medium carries several data streams at the same time.
• Bubble sort


  A sorting algorithm where during a pass, neighbouring values are compared and swapped. Passes are made until no further swaps are needed.
• Cipher text


  Message data after it has been encrypted.
• Circular queue


  When the array element with the largest possible index has been used, the next element to join the queue reuses the vacated location at the beginning of the array.
• Class definition

  A template that can be used to create objects of that class.
• Client


  A computer that uses the services provided by a server.
• Client-server system


  A system in which some computers (the clients) request services provided by other computers (the servers).
• Closed path/circuit


  A sequence of edges that start and end at the same vertex and such that any two successive edges in the sequence share a vertex.
• Communication protocol


  A set of agreed signals, codes, and rules to be used for data and information exchange between computers.
• Complexity of a problem


  Taken to be the worst-case complexity of the most efficient algorithm which solves the problem.
• Composite key


  A combination of attributes that uniquely identifies a tuple/record.
• Computational complexity


  A measure of how economical an algorithm is with time and space.
• Composition


  A type of association where the composite object has ownership of the objects within it. The objects that are part of the composite objects have a lifecycle determined by the composite object. If the composite object ceases to exist then they too will cease to exist.
• Conceptual model


  A representation of the data requirements of an organization constructed in a way that is independent of any software that is used to construct the database.
• Cryptanalysis


  A method of trying to find the plaintext from the ciphertext without the decryption key.
• Cryptography


  The science of designing cipher systems.
• Cycle


  A closed path in which all the edges are different and all the intermediate vertices are different.
• Data Model


  A method of describing the data, its structure, the way it is interrelated, and the constraints that apply to it for a given system or organization.
• Data transmission


  Movement of data.
• Database


  A structured collection of data.