Introduction to Computers/Data sizes and speeds

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Introduction to Computers → Data sizes and speeds This page is part of the Introduction to Computers project.

Contents 1 Names for different sizes of data 1.1 Bit 1.2 Byte 1.3 kB 1.4 MB 1.5 GB 1.6 TB 1.7 PB 2 Measurements of Data Speed 2.1 Bps 2.2 Kbps 2.3 Mbps 2.4 Gbps

[edit] Names for different sizes of data

When choosing a new computer we come across terms such as "300GB hard drive" and "500MB download", and to the uninitiated, this can be somewhat disconcerting. Data in a computer is represented in a series of bits. Since the birth of computers, bits have been the language that control the processes that take place inside that mysterious black box called your computer. In this article, we look at the very language that your computer uses to do its work.

[edit] Bit

A bit is simply a 1 or a 0. A true or a false. It is the most basic unit of data in a computer. It's like the dots and dashes in Morse code for a computer. It's also called machine language.

[edit] Byte

In computer science a byte is a unit of measurement of information storage, that equals '8 bits', can be used to represent letters and numbers. For example, the number 01000001 is 8 bits long, and represents the letter A in ASCII.

[edit] kB

A kB is a unit of data that equals 1024 bytes. This is because 8 bytes cannot contribute into 1000.

[edit] MB

Megabyte is 1024kB squared, 1024²

[edit] GB

A gigabyte is a unit of data storage worth a billion bytes meaning either exactly 1 billion bytes (1024³) or approximately 1.07 billion bytes. More often than not in advertising, Gigabytes are presented as 1 billion bytes and not 1024³ (read the fine print in your adverts!). This explains why a freshly formatted 500GB hard drive shows up at a 450GB one instead. Not too long ago many people were discussing storage in Megabytes. These days, storage has become so cheap that having Gigabytes is considered the norm.

[edit] TB

A terabyte is 1024⁴ and is defined as about one trillion bytes, or 1024 gigabytes. Data centres such as those operated by Google handle thousands if not millions of terabytes of data each day. As storage becomes cheaper and faster, terabytes are becoming a commonly heard term.

[edit] PB

A petabyte is a unit of information or computer storage equal to one quadrillion bytes (1024⁵). Microsoft stores on 900 servers a total of approximately 14 petabytes.

[edit] Measurements of Data Speed

Today there are generally 2 ways of describing data transfer speeds: in bits per second, or in bytes per second. As explained above, a byte is made of 8 bits. Network engineers still describe network speeds in bits per second, while your internet browser would usually measure a file download rate in bytes per second. A lowercase "b" usually means a bit, while an uppercase "B" represents a byte.

[edit] Bps

Known as bits per second, bps was the main way of describing data transfer speeds several decades ago. Bps was also known as the baud rate, therefore, a 600 baud modem was one which could transfer data at around 600bps.

[edit] Kbps

kilobits per second, or 1000 bits per second.

[edit] Mbps

1,000,000 bits per second (usually used in describing internet download/upload speeds).

[edit] Gbps

1,000,000 kilobits per second or 1,000,000,000 bits per second. This term is most commonly heard in local area networks, where the close proximity of machines allows for lightning fast data transfer rates.