Primary Storage: RAM & ROM (OCR GCSE Computer Science): Revision Notes

Primary Storage: RAM & ROM

The Need for Primary Storage

Primary storage (also called main memory) is essential for a computer to function. It holds data and instructions that the CPU (Central Processing Unit) needs while a computer is running.

Why Computers Have Primary Storage

• Fast Access: Primary storage provides fast access to data that the CPU needs immediately, which is much quicker than retrieving data from secondary storage (like a hard drive or SSD).
• Temporary Storage: It temporarily stores data and instructions while the computer is powered on, allowing the CPU to quickly fetch and execute them.
• Necessary for Functioning: Without primary storage, the CPU would not be able to process instructions in real-time, slowing down the system drastically.

Components of Primary Storage

Primary storage typically consists of RAM and ROM:

• RAM (Random Access Memory)
• ROM (Read-Only Memory)

The Difference and Purpose of ROM and RAM

Random Access Memory (RAM)	Read Only Memory (ROM)
Purpose: Stores data and programmes currently being used by the computer	Purpose: Stores instructions needed to start up the computer – contains the boot programme
Can be changed by the computer at any time	Programmed during the computer's manufacture and cannot normally be changed
Volatile memory (data is lost when the power is turned off)	Non-Volatile (data is not lost when the power is turned off)
Larger memory (Starting at 4GB in most computers)	Small (Only MB needed for the boot programme)
The more RAM, the more programmes that can be run at the same time. Allows for more multitasking.	ROM is needed as it is always there to start the computer