Bittipituus

Bittipituus, or bit length, is a measure of how many binary digits are required to represent a value in binary form. It is a fundamental property of data representations, affecting how much memory is needed, how values are stored, and how many different values can be encoded.

In computer systems, many data types use fixed bit lengths, such as 8, 16, 32, or 64 bits. Fixed-width representations determine the range of representable values and the amount of storage they occupy. Some languages and environments also support arbitrary-precision integers, in which the bit length grows with the magnitude of the value, at the cost of variable storage.

For unsigned integers, a b-bit representation can encode 2^b distinct values, from 0 to 2^b − 1. For signed integers, common layouts include two's complement, which yields ranges such as −2^(b−1) to 2^(b−1) − 1. Examples: 8-bit unsigned max 255; 8-bit signed range −128 to 127. A 32-bit unsigned integer ranges up to 4,294,967,295, while a 32-bit signed integer ranges from −2,147,483,648 to 2,147,483,647.

In text encoding, bit length relates to how characters are stored. ASCII uses 7 bits per character (often padded to 8 bits in a byte), while UTF-8 encodes code points in 8-bit units with 1–4 bytes per character.

Bit length can be determined as floor(log2(n)) + 1 for a positive integer n; for zero, definitions vary. Bit length influences memory usage, data transfer, addressing space, and cryptographic key sizes, making it a central concept in computing and information theory.