Definition
A bit is the basic unit of information in computing. Bits can only have one of two values, commonly represented as either a 0 or 1. A sequence of bits is called a bitstream.
Introduction
The term bit is a portmanteau of "binary digit." Bits are numbers expressed in the base two numeral system (i.e., binary system), which only uses two symbols.
Bits are grouped into bytes. Usually eight bits form one byte, but it can vary depending on the computer system.
Binary (base two) and decimal (base ten) measurements
Binary vs decimal
In a binary system, each digit can have one of two values (0 or 1). In a decimal system, each digit can have one of ten values (0 to 9).
Data storage
Binary systems can only have two different numerals. Early computer engineers erroneously adopted the decimal system (SI prefixes) to measure bits and bytes that actually exist in a binary system. In other words, the industry began referring to 1,024 kilobytes (210) as 1,000 kilobytes (103). The international community has adopted specific terminology to measure computer bits but computer storage manufacturers continue to use SI measurements.
Data transmission
Data transmission rates are also measured with SI prefixes. The rate of transmission is measured in bits per second (bit/s or bps). For example:
- Kbps (or kbits/s) denotes 100 bits per second
- Mbps (or mbit/s) denotes 1,000 bits per second
Computer systems can transmit bits one at a time (a serial transmission) or in multiples (a parallel transmission).
Related technical standards
| Standard | Description |
|---|---|
| ISO 80000-1:2009 – Quantities and units – Part 1: General | ISO 80000-1:2009 gives general information and definitions concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems, especially the International System of Quantities, ISQ, and the International System of Units, SI. The principles laid down in ISO 80000-1:2009 are intended for general use within the various fields of science and technology and as an introduction to other parts of the Quantities and units series. Ordinal quantities and nominal properties are outside the scope of ISO 80000-1:2009. See Wikipedia article for general information. |
| ISO 80000-13:2008 – Quantities and units - Part 13: Information science and technology | In IEC 80000-13:2008, names, symbols and definitions for quantities and units used in information science and technology are given. Where appropriate, conversion factors are also given. International Standard IEC 80000-13 has been prepared by IEC technical committee 25: Quantities and units, and their letter symbols in co-operation with ISO/TC 12. This standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005. The only significant change is the addition of explicit definitions for some quantities. |
Resources
Further reading
See the Dalhousie Libraries' analog and digital media wiki page on computer hard drives for a list of common hard drive interfaces.
Related terms
Bitstream
Bit rate
Further reading
https://web.archive.org/web/20090912150947/http://www.iec.ch/news_centre/release/nr2005/nr2005.htm