GCSE Computer Science (Edexcel)

Topic Summaries

COMPUTER SYSTEMS: Memory and storage

Primary storage

Primary storage is a computer’s main memory, used by CPU to store program instructions and data while they are being processed. The two main types of primary storage are RAM and ROM.
RAM and ROM both have direct access to the CPU, unlike secondary storage devices.

	RAM (Random Access Memory)	ROM (Read Only Memory)
Purpose	Used for temporary storage of program instructions and data while being processed by the CPU.	Used for permanent storage of program instructions and data, cannot have new data written to it. Typically used to store the BIOS (Basic Input Output System) which is the bootup sequence that loads the operating system from secondary storage into RAM as soon as the computer turns on.
Type of storage	Volatile: data stored is lost when the computer is turned off or loses power.	Non-volatile: data stored is not lost when the computer is turned off or loses power
Notes	Faster than secondary storage devices but more expensive per GB.	Often made from flash memory which cannot be rewritten or added to without being reflashed.

Functions	ROM	RAM
Boots the system	Yes	No
Loads and runs programs	No	Yes
Permanent storage	Yes	No
Fast, temporary data access	No	Yes

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