This key facts covers ROM - Read Only Memory within RAM and ROM for GCSE Computer Science. Revise RAM and ROM in Memory & Storage for GCSE Computer Science with 15 exam-style questions and 16 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 5 of 10 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 10
Practice
15 questions
Recall
16 flashcards
ROM - Read Only Memory
Definition:
ROM (Read Only Memory) is non-volatile memory that stores permanent instructions that rarely or never change. It retains its content even when the power is turned off.
Key Characteristics:
- Non-volatile: Keeps data permanently, even without power
- Read-only: Data is set during manufacturing or programming - cannot be easily changed by normal use
- Permanent storage: Contents remain unchanged for the device's lifetime (in traditional ROM)
- Slow write speed: If writable at all, writing is much slower than reading
- Critical instructions: Stores essential startup code that must never be lost
What ROM Stores:
- BIOS/UEFI Firmware: Basic Input/Output System - the first code that runs when you press the power button
- Boot instructions: Tells the computer how to start up and find the operating system
- POST (Power-On Self-Test): Checks that hardware components are working correctly
- Hardware drivers: Low-level code to communicate with keyboard, screen, storage devices
The Boot Process (Why ROM is Essential):
- Power on: Electricity reaches the motherboard
- ROM activates: CPU executes BIOS code stored in ROM (no operating system loaded yet!)
- POST runs: BIOS tests RAM, checks for keyboard, GPU, storage drives
- Boot device search: BIOS looks for bootable device (hard drive, USB, CD)
- Hand over control: BIOS loads bootloader, which then loads the operating system into RAM