GCSE Computer Science
(OCR) 2026 | Study Guide,
Practice Questions,
Answers, Rationales &
Exam Review | Complete
Ethics Study Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,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
, 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
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
(OCR) 2026 | Study Guide,
Practice Questions,
Answers, Rationales &
Exam Review | Complete
Ethics Study Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,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
, 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
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
