COMPUTER FUNDAMENTALS - Memory Basics

Memory Basics
If your computer's CPU had to constantly access the hard drive to retrieve every piece of data it needs, it would operate very slowly. When the information is kept in memory, the CPU can access it much more quickly.

CPU
Register

Cache

Temporary
Storage
Areas

Level 1

Level 2

RAM

Physical RAM

Virtual Memory

Storage Device Types

ROM / BIOS

Removable Drives

Network/
Internet Storage

Hard Drive

Permanent
Storage Areas

Input Sources

Keyboard

Mouse

Removable
Media

Scanner/Camera/
Mic/Video

Remote
Source

Other
Sources

As you can see above, the CPU accesses memory according to a distinct hierarchy. Most data goes in random access memory (RAM) first. The CPU then stores pieces of data it will need to access, often in a cache, and maintains certain special instructions in the register.

All of the components in your computer, such as the CPU, the hard drive and the operating system, work together as a team, and memory is one of the most essential parts of this team.

You turn the computer on.
The computer loads data from read-only memory (ROM) and performs a power-on self-test (POST) to make sure all the major components are functioning properly.
The computer loads the basic input/output system (BIOS) from ROM. The BIOS provides the most basic information about storage devices, boot sequence, security, Plug and Play (auto device recognition) capability and a few other items.
The computer loads the operating system (OS) from the hard drive into the system's RAM. Generally, the critical parts of the operating system are maintained in RAM as long as the computer is on. This allows the CPU to have immediate access to the operating system, which enhances the performance and functionality of the overall system.
When you open an application, it is loaded into RAM. To conserve RAM usage, many applications load only the essential parts of the program initially and then load other pieces as needed.
After an application is loaded, any files that are opened for use in that application are loaded into RAM.
When you save a file and close the application, the file is written to the specified storage device, and then it and the application are purged from RAM.