OCR GCSE Computer Science J277 - Systems Architecture

Vocabulary flashcards covering CPU architecture, components, registers, buses, primary and secondary memory, and peripheral devices for OCR GCSE Computer Science.

Central Processing Unit (CPU)

The main processing component (or 'brains') of a computer system that controls all processing, carries out instructions, processes data, retrieves data/instructions from main memory, and stores data into main memory once executed.

Fetch-Execute Cycle

The process performed by the CPU consisting of three stages: Fetching the next instruction and associated data from main memory, Decoding (interpreting) the instruction, and Executing (performing) the instruction.

Fetch Stage

The stage of the CPU cycle where the next instruction and associated data are retrieved from main memory.

Decode Stage

The stage of the CPU cycle where the instruction is interpreted and decoded.

Execute Stage

The stage of the CPU cycle where the decoded instruction is performed.

Control Unit (CU)

A core CPU component that coordinates all operations carried out by the computer, monitors hardware, manages input/output devices, controls data flow within the CPU, and sends control signals such as Memory Read and Memory Write.

Arithmetic Logic Unit (ALU)

A CPU component that performs arithmetic operations (addition, subtraction, multiplication, division) and logical operations (such as basic AND/OR calculations).

Registers

Immediate memory located on the CPU; very fast temporary memory used to hold data or instructions to speed up access.

General-Purpose Registers

Registers on the CPU that temporarily hold data or can be used directly by a programmer.

Program Counter (PC)

A special-purpose register that holds the memory address of the next instruction to be executed, incrementing after the fetch stage.

Accumulator (ACC)

A special-purpose register that holds the result of a calculation performed by the Arithmetic Logic Unit.

Cache

A small bank of very fast memory built directly within or sitting between the processor and main memory that temporarily holds commonly used instructions to allow faster processing.

Memory Hierarchy (Speed vs. Size)

The structural comparison of memory components where Registers have the highest speed and smallest size, Cache is intermediate, and Main Memory has lower speed and larger size.

System Bus

A set of parallel wires connecting two or more independent computer components in order to pass signals between them, divided into the address bus, data bus, and control bus.

Address Bus

A uni-directional bus that carries memory addresses generated by the processor to main memory or other I/O devices.

Data Bus

A bi-directional bus that carries data and instructions between the processor and main memory or secondary storage devices.

Control Bus

A bus along which control signals (such as Memory Read and Memory Write) are sent to instruct which data will travel to or from memory.

Peripherals

External devices not directly connected to the CPU (such as keyboards, mice, printers, and hard disk drives), also referred to as I/O devices.

I/O Controllers

Components that provide an interface between an external hardware device (such as a keyboard, mouse, disk drive, or VDU) and the processor itself.

I/O Ports

Interfaces that allow communication between an I/O device and the motherboard (and hence the CPU).

Random Access Memory (RAM)

Volatile primary memory located on the motherboard that holds data and instructions currently in use by the processor and loses all contents when power is turned off.

Read Only Memory (ROM)

Non-volatile primary memory with permanently etched instructions (such as the Bootstrap Loader) that remain on the chip when power is turned off.

Bootstrap Loader

A program stored in ROM that gives the instructions to start up the Operating System.

EEPROM

Electronically Erasable Programmable Read Only Memory; non-volatile memory (e.g., SIM cards or flash memory) where instructions and data can be erased electronically and replaced.

Secondary Storage

Non-volatile storage used for long-term retention of data and instructions, such as hard disk drives, solid state drives, flash memory, DVD-R, and Blu-ray.

Main Computer Components Diagram

The system structure showing the interaction between Input devices, CPU, Main Memory, Secondary Storage, and Output devices.

John Von Neumann Architecture

A computer system model established in 1945 consisting of three main parts: Processor, Main Memory, and Input/Output (I/O).

Detailed CPU and System Architecture Diagram

A complete system block diagram showing the System Clock, CPU internal parts (Registers, Control Unit, ALU, Cache), Primary Memory, Buses, and External Components.