A binary unit of information equal to 8 bits. Unfortunately, the storage of binary numbers in computers is not entirely standardized. Because computers store information in 8-bit bytes (where a bit is a single binary digit), depending on the "word size" of the machine, numbers requiring more than 8 bits must be stored in multiple bytes. The usual FORTRAN77 integer size is 4 bytes long. However, a number represented as (byte1 byte2 byte3 byte4) in a VAX would be read and interpreted as (byte4 byte3 byte2 byte1) on a Sun. The situation is even worse for floating-point (real) numbers, which are represented in binary as a mantissa and characteristic, and worse still for long (8-byte) reals!
The naming of large multiples of bytes follows standard SI prefixes, as summarized in the following table.
Unfortunately, there is some ambiguity in the meanings of the prefixes kilo-, mega-, etc., when applied to units of information. This arose historically out of the fact
that 
, so "kilobyte"
was used to mean 1024 bytes, "megabyte" to mean 
bytes, etc. However, such usage is now deprecated
in favor of the usual SI unit prefixes, and a special set of prefixes have been invented
for binary powers of information units, summarized in the table below.
