Primary Storage (Memory) | 2.1 | OCR GCSE Computer Science

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Primary storage / Main memory

High-speed, internal memory that the CPU can directly access.

What are the 2 main types of main memory?

Random Access Memory (RAM) and Read Only Memory (ROM)

Why is main memory needed?

To provide fast, direct access to the data and instructions needed to run programs and start the computer.

Volatile Memory (RAM)

Temporary memory - this means data is lost when the computer is shut off.

Non-Volatile Memory

Permanent memory - this means data is saved, even when the computer is shut off.

Random Access Memory

Temporary memory that data can be written to and read from.

Read Only Memory

It is non-volatile memory, that can only be read by the CPU, not written to. The contents cannot be changed and can only be viewed.

What does RAM temporarily store?

Data and instructions for programs that are currently running. - It also stores parts of the Operating System (OS) that are currently in use.

What does ROM store?

The instructions required to boot up the computer and load the Operating System (OS). These instructions are called BIOS (Basic Input Output System).

What does the firmware BIOS do?

Checks that the hardware is functioning correctly during the booting up process.

Virtual Memory

Secondary storage used an extra RAM.

When is data moved to Virtual Memory?

1. Computers have a limited amount of RAM - when applications are opened, the RAM fills up with data. 2. When the RAM is at full capacity and needs to be stored further away.

Negatives of virtual memory

- Slower than RAM - Excessive use can cause ''thrashing'' - significantly reducing performance.

Thrashing

When the computer spends too much time moving data between Main Memory and Virtual Memory.