Computer Memory


Computer Memory:

Memory of a Computer is any physical device that is capable of storing information whether it is large or small and stores it temporarily or permanently. Memory can be either volatile or non-volatile.

Volatile memory is a type of memory that loses its contents when the computer or hardware device is switched off. RAM is an example of a volatile memory. Non-volatile memory is a memory that keeps its contents saved even in the case of power loss. ROM is an example of non-volatile memory. 

Characteristics of Main Memory 

·         Known as the main memory.

·         Semiconductor memories.

·         Faster than secondary memories.

·         A computer cannot run without the primary memory.

·         It is the working memory of the computer.

·         Usually volatile memory.

·         Data is lost in case power is switched off.

Units of Memory

A computer processor is made up of multiple decisive circuits, each one of which may be either OFF or ON. These two states in terms of memory are represented by a 0 or 1.A group of eight bits is known as a byte. 1 byte can represent numbers between zero (00000000) and 255 (11111111), or 28 = 256 distinct positions.

Types of various Units of Memory- 


In computer systems, a unit of data that is eight binary digits long is known as a byte. A byte is a unit that computers use to represent a character such as a letter, number, or a typographic symbol (for example, “h”, “7”, or “$”).

A byte is abbreviated with a big “B” whereas a bit is abbreviated with a small “b”. Computer storage is generally measured in multiples of the byte.


The kilobyte is the smallest unit of memory measurement but greater than a byte. A kilobyte is 103 or 1, 000 bytes abbreviated as ‘K’ or ‘KB’. Kilobytes are mostly used to measure the size of small files. For example, a simple text document may contain 10KB of data and therefore it would have a file size of 10 kilobytes.


One gigabyte is equal to 1, 000 MBs and precedes the terabyte(TB) unit of memory measurement. It is abbreviated as “GB”. Gigabytes, are sometimes also abbreviated as “gigs, ” and are often used to measure storage device’s capacity. e.g., a standard DVD drive can hold 4.7 GBs of data.


One terabyte is equal to 1, 000 GBs and precedes the petabyte(PB) unit of memory measurement. It is abbreviated as “TB”. HDDs are measured in Terabytes e.g., a typical internal HDD may hold 2 Terabytes of data whereas some servers and high-end workstations that contain multiple hard drives may even have a total storage capacity of over 10 Terabytes.  


One petabyte is equal to 1, 000 TBs and precedes the Exabyte unit of memory measurement. It is abbreviated as “PB”. Internet Giants like Google and Facebook store more than over 100 PBs of data on their data servers. 


One Exabyte is equal to 1, 000 PBs and precedes the zettabyte unit of memory measurement. An Exabyte is abbreviated as “EB”. The Exabyte unit of memory measurement is so large, that it is not used to measure the capacity of storage devices. Even the data storage capacity of the biggest cloud storage centers is measured in Petabytes, which is a fraction of 1 EB.


Zetta Byte

One zettabyte is equal to 1, 000 exabytes .A zettabyte is abbreviated as “ZB”. One zettabyte contains one billion TBs or one sextillion bytes which means it will take one billion one terabyte hard drives to store one zettabyte of data. Generally, Zettabyte is used to measure the large amounts of data and all the data in the world is just a few zettabytes.  

Yotta Byte

One yottabyte is equal to 1, 000 zettabytes. It is the largest SI unit of memory measurement. A yottabyte is 1024 ZettaBytes  and is abbreviated as “YB”. 1 yottabyte contains one septillion bytes which are exactly the same as one trillion TBs. It is a very large number that humans can evaluate. There is no practical use of such a large measurement unit because all the data in the world made of just a few zettabytes. 

Some Misconceptions

The size on a disk with one KB is 1024 Bytes although it signifies 1, 000 Bytes of data. It’s just the old standard everyone remembers. The download speed Kbps is 1,000 Bits per second, not 1,024 Bits per second.

Tabular Representation of various Memory Sizes


Equal To

Size (In Bytes)


1 Bit



4 Bits

1/2 (rare)


8 Bits



1024 Bytes



1, 024 Kilobytes

1, 048, 576


1, 024 Megabytes

1, 073, 741, 824


1, 024 Gigabytes

1, 099, 511, 627, 776


1, 024 Terabytes

1, 125, 899, 906, 842, 624


1, 024 Petabytes

1, 152, 921, 504, 606, 846, 976


1, 024 Exabytes

1, 180, 591, 620, 717, 411, 303, 424


1, 024 Zettabytes

1, 208, 925, 819, 614, 629, 174, 706, 176

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