Paper 1 definitions Flashcards
ALU
Arithmetic logic unit: The part of the CPU where data is processed and manipulated. This processing and manipulation normally consists of arithmetic operations or logical comparisons allowing a program to make decisions
Control Unit
The part of the CPU that manages the execution of instructions. The control unit fetches each instruction in sequence and decodes and synchronises it before executing it by sending control signals to other parts of the compter
Register
Tiny areas of extremely fast memory located in the CPU normally designed for a specific purpose, where one piece of data or control information in stored temporarily
PC
Program counter: A register in the control unit which holds the address of the next instruction to be executed
ACC
Accumulator: A special register which holds the data currently being processed by the central processor. Any data to be processed is stored temporarily in the accumulator.
MAR
Memory Address Register: A register in the CPU that stores the address of the memory location currently in use. In the fetch phase, this is the address of the data being used
MDR
Memory Data Register: A register in the CPU that stores data being transferred to and from the immediate access store. It acts as a buffer, allowing the central processor and memory unit to act independently without being affected by minor differences in operation. A data item will be copied to the MDR ready for use at the next clock pulse where it can either be used by the central processor or stored in memory
CIR
Current Instruction Register: A register in in the control unit that stores the address of the next instruction currently being executed and decoded
Buses
A common physical pathway (wire) shared by signals to and from several components of a computer
Data Bus
The part of the bus which carries the actual information
Control Bus
The part of the bus which carries identification about where the data is being sent
Fetch-Decode-Execute
The complete process of retrieving an instruction from store, decoding it and carrying it out
CPU
Central Processing Unit: The main part of the computer consisting of the registers, ALU and control unit
Clock Speed
Measured in Hertz- the frequency at which the internal clock generates pulses. The higher the clock rate, ht faster the computer may work. The clock is the electronic unit that synchronises related components by generating pulses at a constant rate
Cores
A part of a multi-score processor, which is a single component with 2 or more independent actual CPUs which are the units responsible for the FDE cycle
Cache
A part of the main store between the central processor and the rest of the memory. It has extremely fast access, so sections of a program and its associated data are copied their to take advantage of its short fetch cycle
Von Neumann Architecture
Traditional computer architecture that forms the basis of most digital computer systems. A single control unit manages program control flow following a linear sequence of fetch-decode-execute
Embedded systems
A small computer that is part of a wider device or machine, it includes hardware and software and allows users to interact with the machine. eg central heating, washing machines, dishwashers
RAM
Random Access Memory: Volatile main memory with very fast access times. Contains operating system, current instructions and data, and open files or software
Virtual Memory
Part of a disk drive allocated to be used as if it were main memory. It is very slow, and the software will attempt to use the immediate-access store if possible
Volatile
Memory that loses its content when the power is turned off
Non-Volatile
Memory that retains its data when it loses power
Bootstrap Loader
The first program to be loaded into RAM when the device is turned on
POST
Power On Self-Test: determines if all the necessary components are connected and running correctly