6bit

6bit refers to a unit of data consisting of six binary digits. In computing, six-bit word sizes and six-bit character encodings were used on some early hardware to save memory and simplify circuitry. A 6-bit unit can represent 64 distinct values, which limited the amount of information that could be stored or transmitted in a single symbol.

The most well-known six-bit character encoding is DEC SIXBIT, used on DEC’s PDP-6, PDP-10, and related systems. SIXBIT assigns 64 code points to uppercase letters, digits, and a selection of punctuation, with text stored as sequences of 6-bit characters packed into larger words. These machines typically used word widths of 36 or 72 bits, allowing multiple six-bit characters per word.

Six-bit units also appear in other data-encoding schemes that operate on 6-bit chunks. For example, base64 and similar binary-to-text encodings map 6-bit groups to printable characters, enabling efficient text representation of binary data. In graphics, the term 6-bit color can describe color configurations where a pixel uses six bits (such as two bits per RGB channel, yielding 64 possible colors). Modern displays and software, however, typically employ wider color and character encodings.

Modern relevance of six-bit systems is mostly historical or in retrocomputing contexts. The prevalence of 8-bit bytes, along with ASCII and Unicode character sets, has diminished the practical use of six-bit encodings. Nonetheless, understanding six-bit representations helps explain the evolution of data encoding, memory optimization, and early computer architecture.