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1 Petabyte 1PB 1024 TB

1 Exabyte 1EB 1024 PB

1 Zettabyte 1ZB 1024 EB

1 Yottabyte 1YB 1024 ZB

Memory Size Units

Primary Storage Devices

Primary storage devices are the computer's main memory. They store data and

instructions temporarily while the computer is working. These are fast and help the
computer work quickly.

Two main types are RAM and ROM.

RAM (Random Access Memory)

• RAM is a type of primary memory in a computer.
• It stores data and programs temporarily while we are

using the computer.

• When we open a game or a file, it is first loaded into RAM
so the computer can work on it quickly.

• RAM is fast, but the data is lost when the computer is turned off.

It is of two types:

SRAM (Static RAM)

Faster and more expensive. Used in cache memory (a
small memory that helps the computer work faster).
Does not need to be refreshed repeatedly.

DRAM (Dynamic RAM)

Slower but cheaper than SRAM.

Used as the main memory in computers.

Needs to be refreshed many times every second to
keep data.

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