GCSE key terms Flashcards
What does the ALU stand for?
Arithmetic Logic Unit
What does the ALU do?
The part of the CPU where data is processed.
This is normally arithmetic operations/logical comparisons so a program can make decisions
what does the CU do?
manages execution of instructions.
Fs, Ds and Es instructions by sending control signals to other components
what is a register?
tiny, fast memory in cpu,
designed for a specific purpose
temporarily stores 1 piece of data/control info
what does the PC do?
Holds the address of the next instruction to be executed
what is the ACC?
register in the ALU
holds data currently being processed.
What does PC stand for?
Program Counter
What does ACC stand for?
Accumulator
What does the MAR contain?
the address of the memory location in use.
in fetch it’s the instruction being loaded
in excecute it’s the address of the data being used
What does the memory data register (MDR) do?
holds the data/instruction ready for transfer to or from memory
What is the CIR?
A register in the CU that stores the address of the instruction currently being executed and decoded
What does MAR stand for?
Memory Address Register
What does MDR stand for?
Memory Data Register
What does CIR stand for?
Current Instruction Register
What is a bus?
A common physical pathway, a wire, shared by signals to and from several components of a computer
What is a data bus?
The part of a bus that carries data
What is an address bus?
The part of a bus that
carries identification about where the data’s being sent
What is a control bus?
A bus that carries command and control signals to and from every component of a computer
What is the Fetch-Decode-Execute cycle?
The complete process of recieving an instruction from store, decoding it and carrying it out
What is the instruction cycle?
Another name for the FDE cycle
What is the CPU?
the main part of a computer: contains registers, ALU+CU
What is clock speed?
the frequency at which the internal clock generates pulse. higher clock speed, faster computer.
the clock is the component that synchronises other components by generating regular pulses
What is clock speed measured in?
Hertz
What are cores?
A part of a multi-core processor (single components with at least independant CPUs)
What is Von Neumann architecture?
Traditional computer architecture where one CU manages program control flow following a linear sequence of FDE
what are embedded systems?
A small computer-hard and software- part of a larger device
allows users to interact w/ the device
Give some examples of embedded systems
Central heating systems, dishwashers, washing machines, engine management systems in cars
What is RAM?
fast, volatile main memory.
When used as main memory, RAM typically can be thought of as containing the OS, programs in use, and data used by those programs
What does RAM stand for?
Random Access Memory
What are the contents of RAM?
The OS
current instructions / data
any open files / software
What is ROM?
Memory where the contents can be read but not changed.
Software is fixed during manufacturing.
Typically holds system boot up instructions.
Can ROM be written to?
No, but more modern versions- *(PROM, EPROM and EAROM) *can
What does ROM stand for?
Read Only Memory
What is stored in the ROM?
POST and BIOS (power on self test and basic input output system)
What is virtual memory?
where part of secondary storage is allocated to be used as if it were main memory when RAM is full.
very slow, so the software will attempt to use RAM if possible
What is Flash Memory?
A type of very fast-access non-volatile memory
What does POST stand for, and what does it do?
Power On Self Test- detirmines if all components are connected and running correctly
What does BIOS stand for?
Basic Input and Output System
What does volatile mean?
Memory that loses its contents when the computer is turned off
What is a bootstrap loader?
first program loaded to RAM when the device turns on
What does speed refer to? (storage)
The relative speed at which data can be accessed by each type of device
What is magnetic storage?
Uses surfaces coated with a layer of mag material
data stored by setting arrangement of the mag. material.
with electromag r/wr heads
What is flash storage?
A collection of memory chips controlled by their own software to make the chips act like a hard drive
What is optical storage?
Storage medium using plastic discs to store data in pits + lans
What is a lan? (not LAN)
A “bump” in optical storage, as opposed to a pit. also called a fall
What is capacity?
The amount of data a device can store
What is capacity measured in?
Bytes
What is robustness?
The amount of physical damage a device can take before it breaks
How do you measure how expensieve a storage device is?
In cost per gigabit
What do you call the way to compare how much physical damage a device can take?
robustness
What is a sector?
A subdivision of the magnetic disk
What is a platter?
A circular disk on which magnetic data is stored. They spin quickly so the read head can recieve the data
What is a track?
a circular path on the surface of the disk where data is stored
what is speed(referring to different storage devices)
the relative access speed of each device
What are the different ways of measuring the effectiveness of different storage devices?
Capacity, durability, robustenss, speed, cost per gigabit, portability
What does HDD stand for?
Hard Disk Drive (magnetic)
What does SSD stand for?
Solid State Drive , uses flash memory
What is an SD card?
Small, portable devices that use flash memory to store data, used in phones, cameras, etc
What is a data pen/stick?
A small device that uses flash memory to store data
What type of memory do data sticks use?
flash memory
What does DVD stand for?
Digital Versatile Disk
What type of storage is a DVD?
optical
What does CD stand for?
Compact Disk
What type of storage do CDs use?
optical
what type of storage do blu-rays use?
optical
what is a bit?
a single unit of data; a 1 or a 0
what is a byte?
8 bits of data
what is a nibble?
4 bits of data, or half a byte
how many bytes are there in a kilobyte?
1,000 or 10 ^3
how many bytes are there in a terabyte?
1,000,000,000,000 or 10^12
how many bytes are there in a gigabyte?
1,000,000,000 or 10^9
how many bytes are there in a petabyte?
1,000,000,000,000,000 or 10^15
how many bytes are there in a megabyte?
1,000,000 or 10^6
what is the order of the standard form prefixes, going up in 10^3s?
kilo,mega,giga,tera,peta
what is a number base?
the positional number system
using unique digits to display quantities,
digits are resused and their position represents higher or lower values
what is denary?
base 10
what is binary?
base 2- 0 and 1
what is hexadecimal?
base 16, uses denary and A,B,C,D,E to represent 10-15
what is a left shift?
By shifting a binary number to the left and placing a zero in the least significant column. this doubles the number (as a left shift in denary would multiply the number by 10)
what is a right shift?
the reverse process of a left shift, divides the number by 2
what is a character set?
the collection of letters, symbols and digits that a computer can represent
what does ASCII stand for?
American Standard for Information Interchange
How many bits does ASCII use?
7/8 (uses 7, stored as 8)
What is an uppercase A in ASCII?
65
What is a lowercase a in ASCII?
97
What does pixel stand for?
Picture Element
What is metadata?
the information at the beginning of a file, usually the length and height, colour depth, type of file, etc
what is colour depth?
the number of colours used in an image
(3 bit = 2^3 = 8 colours)
how many colours would you get in 6 bit colour depth?
2^6 or 64 colours
What is resolution?
the number of dots per inch used in the image file