GCSE Computer Science OCR: Revision Bundle (for exams in 2022 and
beyond)
Arithmetic Logic Unit (ALU) - Performs operations on data e.g. Addition,
subtraction
Control Unit (CU) - Coordinating activities of the CPU
Registers - Quick, small stores of data within the CPU
Memory Address Register (MAR) - Holds memory address for data or a
instruction about to be used by the CPU
Memory Data Register (MDR) - Holds actual data or instruction
Accumulator - Stores results of calculations in the ALU
Program Counter (PC) - Holds memory address of the instruction for each
cycle
Fetch - The next instruction is retrieved by CPU from main memory
Decode - The instruction is broken down and decided so computer can
understand
Execute - The CPU performs what the instructions told
Embedded System - A computer system built within a large device e.g.
Camera, washer, car
Volatile - Memory loses its data when power of
,GCSE Computer Science OCR: Revision Bundle (for exams in 2022 and
beyond)
Non-volatile - Memory retains its data when power is lost
Random Access Memory (RAM) - Read/write - function is to load open
programs and operating system data currently in use - volatile
Read Only Memory (ROM) - Can only be read, can't be changed, stores
essential programs to be run in order to boot the computer - non-volatile
Cache - A type memory that stores copies of frequently used data, much
faster than RAM, lower capacity - closer to CPU
Buses - Collection of wires that carry signals between various components of
the computer system
Central Processing Unit (CPU) - Processes all of the data and instructions
that make the system work - can be effected by clock speed, number of
cores, cache size
Clock speed - How fast the computer does the FDE cycle
virtual memory - A memory management procedure needed when the RAM is
full so a temporary section is made which acts like a part of RAM
Flash memory - Solid state storage, non-volatile, more reliable/durable but
can only be overwritten a limited number of times
Graphics Processing Unit (GPU) - Handles graphics and image processing
, GCSE Computer Science OCR: Revision Bundle (for exams in 2022 and
beyond)
Optical storage - CD, DVD, Blue-ray
ADV: cheap,easy to transport
DIS: slow, less storage than hard drives, stored data degrades over time,
cannot be written over
Magnetic storage - Hard drives
ADV: fast access, stores large amounts of data, low cost
DIS: not very portable, easily be broken
Solid State storage - USB, flash memory, SD
ADV: fast, small, light, easily potable, quiet
DIS: more expensive, storage capacity less, limited number erase/write
cycles
Cloud stotage - Data is stored on multiple servers in a remote location
ADV: secure, can be accessed anywhere, no need to buy
DIS: needs internet, download and upload can be effected by internet
connection, less control if data is held
Operating System - essential software that links the hardware and other
software together and generally manages the computer system
Command-line Interface - Text commands where user has to type in
command
Graphical User Interface (GUI) - uses icons and other visual indicators to
navigate and issue commands
beyond)
Arithmetic Logic Unit (ALU) - Performs operations on data e.g. Addition,
subtraction
Control Unit (CU) - Coordinating activities of the CPU
Registers - Quick, small stores of data within the CPU
Memory Address Register (MAR) - Holds memory address for data or a
instruction about to be used by the CPU
Memory Data Register (MDR) - Holds actual data or instruction
Accumulator - Stores results of calculations in the ALU
Program Counter (PC) - Holds memory address of the instruction for each
cycle
Fetch - The next instruction is retrieved by CPU from main memory
Decode - The instruction is broken down and decided so computer can
understand
Execute - The CPU performs what the instructions told
Embedded System - A computer system built within a large device e.g.
Camera, washer, car
Volatile - Memory loses its data when power of
,GCSE Computer Science OCR: Revision Bundle (for exams in 2022 and
beyond)
Non-volatile - Memory retains its data when power is lost
Random Access Memory (RAM) - Read/write - function is to load open
programs and operating system data currently in use - volatile
Read Only Memory (ROM) - Can only be read, can't be changed, stores
essential programs to be run in order to boot the computer - non-volatile
Cache - A type memory that stores copies of frequently used data, much
faster than RAM, lower capacity - closer to CPU
Buses - Collection of wires that carry signals between various components of
the computer system
Central Processing Unit (CPU) - Processes all of the data and instructions
that make the system work - can be effected by clock speed, number of
cores, cache size
Clock speed - How fast the computer does the FDE cycle
virtual memory - A memory management procedure needed when the RAM is
full so a temporary section is made which acts like a part of RAM
Flash memory - Solid state storage, non-volatile, more reliable/durable but
can only be overwritten a limited number of times
Graphics Processing Unit (GPU) - Handles graphics and image processing
, GCSE Computer Science OCR: Revision Bundle (for exams in 2022 and
beyond)
Optical storage - CD, DVD, Blue-ray
ADV: cheap,easy to transport
DIS: slow, less storage than hard drives, stored data degrades over time,
cannot be written over
Magnetic storage - Hard drives
ADV: fast access, stores large amounts of data, low cost
DIS: not very portable, easily be broken
Solid State storage - USB, flash memory, SD
ADV: fast, small, light, easily potable, quiet
DIS: more expensive, storage capacity less, limited number erase/write
cycles
Cloud stotage - Data is stored on multiple servers in a remote location
ADV: secure, can be accessed anywhere, no need to buy
DIS: needs internet, download and upload can be effected by internet
connection, less control if data is held
Operating System - essential software that links the hardware and other
software together and generally manages the computer system
Command-line Interface - Text commands where user has to type in
command
Graphical User Interface (GUI) - uses icons and other visual indicators to
navigate and issue commands
