Systems Architecture is a core part of GCSE Computer Science. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Von NeumannStores data and instructions in same memory.
CPUCentral processing unit — executes instructions.
ALUArithmetic logic unit — does maths and logic.
CUControl unit — directs the CPU's actions.
RAMMain memory holding programs and data in use.
I/OInput and output devices, e.g. keyboard, screen.
FetchGet the next instruction from memory.
DecodeWork out what the instruction means.
ExecuteCarry out the instruction.
PCProgram counter — holds next instruction's address.
MARMemory address register — address being accessed.
MDRMemory data register — data being transferred.
Clock speedHow many cycles a CPU does per second.
GHzGigahertz — 1,000,000,000 cycles per second.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What does the CPU do?✗ Permanently stores all the computer's files. ✓ Processes instructions (fetch–decode–execute).
How do RAM and storage differ?✗ They are the same thing. ✓ RAM is fast, volatile working memory; storage keeps data without power.
What is system software like an operating system for?✗ Doing the user's tasks like writing essays. ✓ Managing hardware and running other software.
What happens when 11111111 + 1 is computed in an 8-bit register?✗ It just becomes 100000000 normally. ✓ Overflow - the result requires 9 bits but only 8 are available.
Practise Systems Architecture — free games
Test yourself with these quick revision games for this topic:
See all 17 games in the Subjects Arcade →
More GCSE Computer Science topics
← All revision guides
Want to revise every topic this smart?
The Velvet Method teaches you to use AI to revise any subject — £25, lifetime access.
Explore the Course →