Computer Science - OCR GCSE - 1.2.1 Primary Memory

Name three types of primary memories:

Name three types of primary memories:

RAM

Cache

ROM

Why is primary storage needed:

Primary storage is used to store currently used data and programs, in RAM and cache.

These are stored in primary storage as it would be too slow for the CPU to fetch and execute these programs from secondary memory.

Describe RAM:

RAM stands for Random Access Memory.

This is a volatile memory, which means that it loses its contents  when the power is  switched off.

It stores programs and data temporarily.

Programs and data are moved into RAM from main storage, such as a hard disk.

Programs and data can only be executed when they are stored in RAM.

RAM is also commonly known as secondary memory.

What type of programs does RAM store?

Applications programs and operating systems.

What is virtual memory?

Section of the hard disk that is used to store programs in RAM that are no longer required.

Why is virtual memory needed in a computer system and how does it work?

Needed:

Required when the system has not got enough to RAM to hold all currently opened programs

How it works:

Programs are transferred from RAM into VM when they are not likely to be needed imminently

Programs in VM can be loaded back in to RAM when they are required by the CPU

Rank the following in terms of speed of data:

RAM, Virtual Memory, Cache Memory

1. Cache Memory

2. RAM

3. Virtual Memory

What is the standard capacity of RAM and Virtual memory compared to Cache memory?

8GB of RAM and Virtual memory compared to around 64MB of Cache memory

How does adding more RAM increase the performance of a computer?

1. Limited RAM means the computer will run out of RAM space quickly

2. This means more programs must be transferred in and out of Virtual Memory

3. Virtual Memory is on secondary storage which is slower form of memory

4. Swapping programs in and out of Virtual Memory will slow down processing time

What is the role of ROM in a computer?

• Contains the bootstrap loader/boot program

• Bootstrap loader loads the OS from the hard disk into RAM when the computer is switched on.

• BIOS (Basic Input Output) settings for a computer

• POST (Power On Self Test) - checks all components in the computer are connected and operational

Explain the differences between RAM and ROM:

• ROM is permanent compared to RAM which is temporary

• ROM is usually 2MB compared to RAMs usual 8GB

• ROM contains the bootstrap which loads the operating system into the RAM. RAM holds parts of the OS currently needed and holds programs currently running (e.g. MS Word) and holds files and data currently being used - e.g. an image

• RAM is volatile and ROM is non-volatile

• ROM is Read only whereas RAM is Read and Write