Byte

The byte (pronounced /ˈbaɪt/), is a unit of digital information in computing and telecommunications, that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and it is for this reason the basic addressable element in many computer architectures. The size of the byte has historically been hardware dependent and no definitive standards exist that mandate the size. The de facto standard of eight bits is a convenient power of two permitting the values 0 through 255 for one byte. Many types of applications use variables representable in eight or fewer bits, and processor designers optimize for this common usage. The byte size and byte addressing are often used in place of longer integers for size or speed optimizations in microcontrollers and CPUs. Floating point processors and signal processing applications tend to operate on larger values and some digital signal processors have 16 to 40 bits as the smallest unit of addressable storage. On such processors a byte may be defined to contain this number of bits. The popularity of major commercial computing architectures have aided in the ubiquitous acceptance of the 8-bit size.

 

The byte is also defined as a data type in certain programming languages. The C and C++ programming languages, for example, define byte as an "addressable unit of data large enough to hold any member of the basic character set of the execution environment" (clause 3.6 of the C standard). The C standard requires that the char integral data type is capable of holding at least 255 different values, and is represented by at least 8 bits (clause 5.2.4.2.1). Various implementations of C and C++ define a byte as 8, 9, 16, 32, or 36 bits^[8][9]. The actual number of bits in a particular implementation is documented as CHAR_BIT as implemented in the limits.h file. Java's primitive byte data type is always defined as consisting of 8 bits and being a signed data type, holding values from −128 to 127.
In data transmission systems, a contiguous sequence of binary bits in a serial data stream, such as in modem or satellite communications, which is the smallest meaningful unit of data. These bytes might include start bits, stop bits, or parity bits, and thus could vary from 7 to 12 bits to contain a single 7-bit ASCII code.