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

Processor Components: (incomplete) 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) 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) 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