A-level Computing/AQA/Computer Components, The Stored Program Concept and the Internet/Definitions

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Processor Components: (incomplete)[edit]

Program control unit - Fetches program instructions from memory, decodes them and executes them one at a time.


Arithmetic and logic unit - The ALU performs arithmetic and logical operations on data such as addition and subtraction; fixed-point and floating-point arithmetic; Boolean logic such as AND, OR, NOT, XOR; and a range of shift operations.


Registers - Fast memory locations inside the processor (or an I/O controller) that may be dedicated or general-purpose.


Internal clock - Derived directly or indirectly from the system clock.


Internal buses - Several internal buses link the control unit, the ALU and the registers.


Logic gates - Used for flow control.


Hardware and Software: (incomplete)[edit]

Hardware - The physical components of a computer system


Software - programs understood and executed by the hardware that perform tasks


Application software - Used to perform a task that is independent of computer


System software - Software that performs tasks to run computer


General purpose software - type of software that can be used for a variety of tasks


Special purpose software - type of software created to execute one specific task


Bespoke software - type of software designed specifically for an organisation to do the tasks set out by the organisation


Internetː (incomplete)[edit]

Server - a computer program running to serve the requests of other programs, the "clients”


Client - an application or system that accesses a service made available by a server


Protocol - a set of rules governing the way that devices communicate with each other


Port number - an application or process specific communication endpoint attached to an IP address


URI - A character string identifying a resource on the internet


Internet - a global system of interconnected computer networks that use the standard Internet Protocol suite (TCP/IP)


World Wide Web - a system of interlinked hypertext documents accessed via the internet using the http protocol


Router - a device that interconnects with two or more computer networks, which then interchange packets with each other