🎓✨ GCSE COMPUTER SCIENCE NOTES
✨🎓
OCR (Oxford, Cambridge and RSA) Exam Board
📚 Your Ultimate Study Guide for Exam Success! 📚
✅ Understand core concepts clearly
✅ Revise efficiently with structured summaries
✅ Test yourself with exam-style questions and answers
✅ Learn visually with helpful diagrams and examples
✨ Clear • Concise • Exam-Focused • Student-Friendly ✨
, PAPER 1 – Computer Systems
1. Systems Architecture
CPU (Central Processing Unit): The brain of the computer. Executes instructions using:
o ALU (Arithmetic Logic Unit): Performs calculations and logical decisions.
o CU (Control Unit): Directs data flow between CPU and other components.
o Registers: Small memory areas for fast access to instructions/data.
FDE Cycle: Instructions go through Fetch → Decode → Execute.
Performance Factors:
o Clock speed (measured in GHz): Faster clock = more instructions per second.
o Cache size: Bigger cache = quicker access.
o Cores: Multiple cores = multitasking capability.
2. Memory and Storage
Primary Memory:
o RAM: Temporary, volatile memory; data lost when power off.
o ROM: Permanent, non-volatile; stores BIOS/start-up routines.
Virtual Memory: Uses secondary storage when RAM is full — slows performance.
Secondary Storage:
o HDD (Magnetic): Large capacity, slower.
o SSD (Solid State): Faster, durable, no moving parts.
o Optical (CD/DVD): Used for media.
o Cloud Storage: Accessible online, requires internet.
Storage Metrics: Bit → Byte → KB → MB → GB → TB.
Compression:
o Lossy: Reduces size, loses quality (JPEG).
o Lossless: Retains data (PNG, ZIP).
3. Computer Networks
Types:
o LAN: Local (e.g. school).
o WAN: Wide (e.g. internet).
Advantages of Networks: File sharing, device sharing, centralized backup.
Topologies:
o Star: All connect to a central switch/hub.
✨🎓
OCR (Oxford, Cambridge and RSA) Exam Board
📚 Your Ultimate Study Guide for Exam Success! 📚
✅ Understand core concepts clearly
✅ Revise efficiently with structured summaries
✅ Test yourself with exam-style questions and answers
✅ Learn visually with helpful diagrams and examples
✨ Clear • Concise • Exam-Focused • Student-Friendly ✨
, PAPER 1 – Computer Systems
1. Systems Architecture
CPU (Central Processing Unit): The brain of the computer. Executes instructions using:
o ALU (Arithmetic Logic Unit): Performs calculations and logical decisions.
o CU (Control Unit): Directs data flow between CPU and other components.
o Registers: Small memory areas for fast access to instructions/data.
FDE Cycle: Instructions go through Fetch → Decode → Execute.
Performance Factors:
o Clock speed (measured in GHz): Faster clock = more instructions per second.
o Cache size: Bigger cache = quicker access.
o Cores: Multiple cores = multitasking capability.
2. Memory and Storage
Primary Memory:
o RAM: Temporary, volatile memory; data lost when power off.
o ROM: Permanent, non-volatile; stores BIOS/start-up routines.
Virtual Memory: Uses secondary storage when RAM is full — slows performance.
Secondary Storage:
o HDD (Magnetic): Large capacity, slower.
o SSD (Solid State): Faster, durable, no moving parts.
o Optical (CD/DVD): Used for media.
o Cloud Storage: Accessible online, requires internet.
Storage Metrics: Bit → Byte → KB → MB → GB → TB.
Compression:
o Lossy: Reduces size, loses quality (JPEG).
o Lossless: Retains data (PNG, ZIP).
3. Computer Networks
Types:
o LAN: Local (e.g. school).
o WAN: Wide (e.g. internet).
Advantages of Networks: File sharing, device sharing, centralized backup.
Topologies:
o Star: All connect to a central switch/hub.
