Binary-coded decimal Binary-coded decimal In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight. Special bit patterns are sometimes used for a sign or for other indications (e.g., error or overflow). In byte-oriented systems (i.e. most modern computers), the term "unpacked" BCD usually implies a full byte for each digit (often including a sign), whereas "packed" BCD typically encodes two decimal digits within a single byte by taking advantage of the fact that four bits are enough to represent
Byte addressing systems, such as the PDP-10, use word addressing but facilitate access to individual bytes using special instructions which can access memory using a "byte pointer", which contains both a word address and the index of a specific byte within the word. Byte addressing Byte addressing refers to hardware architectures which support accessing individual bytes of data rather than only larger units called words, which would be "word-addressable". Such computers are sometimes called "byte machines" (in contrast to "word machines"). The basic unit of digital storage is called a bit, storing a single 0 or 1. Many common architectures can address