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
Speed
The relative speed that data can be accessed by each type of device
Storage Device
Any medium which holds data or programs
Magnetic Storage
A storage medium which uses surfaces coated with a layer of magnetic material on which data can be stored by magnetically setting the arrangement of the magnetic material. This is done by electromagnetic read/write heads
Flash Storage
A collection of memory chips that is controlled by its own software to make the collection of chips act like a disk drive
Optical Storage
A storage medium that uses plastic discs on which the data is stored as patterns on the surface in pits and lans
Capacity
The amount of data that can be stored on the device, measured in bytes
Robustness
The amount of physical damage that a device can take before it breaks
Cost per Gigabit
A comparison between different storage devices
Platter
A circular disk on which magnetic data is stored. They spin at a high speed so that the reading head can receive the data stored
Sector
A sub division of the magnetic disk, containing a fixed amount of storage space
Track
A circular path on the surface of the disk, where magnetic data is stored
Speed
The relative access speed of each type of device
Portability
The ease with which data is transferred from one location to another whilst being stored on the device
Durability
The ability of the device to withstand knocks and bumps without becoming damaged
Reliability
The approximate lifespan of a device
Pits and falls
The reflective/non-reflective parts of an optical disk that store data
HDD
Hard disk drive, a storage media that stores data as magnetic elements
SSD
Solid state drive- uses flash memory to store data
SD card
Small, portable devices that use flash memory to store data, found in phones, cameras, etc
Data pen/stick
Physically small devices that use flash memory to store data- usually connects to a computer via the USB port
DVD
Digital versatile disk- uses optical methods to store data
CD
Compact disk- uses optical methods to store data
Bit
A single unit of data, usually modelled as 1 or 0
Byte
8 bits of data
Nibble
4 bits of data
Kilo
1000 bits of data
Mega
1,000,000 bits of data
Giga
1,000,000,000 bits of data
Tera
1,000,000,000,000 bits of data
Peta
1,000,000,000,000,000 bits of data
Number base
The positional number system, using unique digits to display quantities, digits are reused and their position displays higher or lower quantities
Denary
Base 10
Binary
Base 2
Hexadecimal
Base 16
Right shift
By shifting a binary number to the right by one column and placing a zero in the least significant column, the number can be doubled
Left shift
The reverse process to a right shift, the number halves
Character set
The collection of symbols, letters and digits that can be represented on a computer
ASCII
American standard for information interchange- a character set
UNICODE
A much larger character set that includes more characters than UNICODE
Pixel
One graphical dot
Metadata
The information at the beginning of a (picture) file, usually the length, height, colour depth and the type of file
Colour depth
The number of colours used in an image (3 bits = 2x2x2 = 8 colours)
Resolution
The number of dots per inch in an image file
Sampling
Sound is gathered at certain intervals (5 times per second)
Sample rate
The rate at which sound is gathered and turned into a digital file
Bit depth
The number of bits available for each sample