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The basics of bits and bytes
Table of Units 听听听
Basic Units 听听听
Unit Abbreviated Unit in Full Explanation Example
b bit bit stands for binary digit 鈥 a 0 or a 1. The basic volume unit of all computer operationsA single bit has no useful meaning in the context of CCTV 鈥 a computer can neither store nor send a single bit
B Byte a byte is made up of eight bits One byte stores a single pixel of an image, or a single character in a text document
Storage Units 鈥 measured in Bytes
Unit Abbreviated Unit in Full Explanation Example
KB (often spoken of as just 鈥渒ay鈥) Kilobyte1000* bytes a single image, or a small video image, takes tens or a few hundreds of KB
MB (often spoken of as 鈥渕eg鈥) Megabyte 1000* KB, and therefore 1 million* bytes big images or an average video sequence may take a few MB to store
GB (often spoken of as 鈥済ig鈥)Gigabyte 1000*Megabytes, thousand million* bytes storage media such as disks are measured in GB. PCs have storage capacity in low GB (such as 40).
TB Terabyte 1000* Megabytes, and therefore 1* million million bytesdedicated storage devices can have capacities up to a few TB
Communications Units 鈥 measured in bits
Unit Abbreviated Unit in Full Explanation Example
Kbps Kilobits per second 1000* bits (or 125* bytes) per second slower line speeds such as PSTN, allow speeds of around 56 Kbps. Broadband Internet allow speeds of Mbps
Mbps Megabits per second 1000*Kbps, which is 1 million* bit per second Local Area Networks and some Public Data Services work at speeds in Mbps 鈥 for example Ethernet LANs operate typically at 10 Mbps, although 100 and 1000 Mbps are available
Communications systems do not yet use giga- or tera- speeds, so the terms are not used
* Purists know that the multiples from Byte all the way up to TB are not truly 1000 but 1024 (strictly 1KB = 1024B). Engineers rarely need to take account of this 2 per cent difference