What is a Bit?

A bit is the most elementary and smallest unit of data storage and communication, which is primarily implemented in the IT and telecommunications domains. It is the largest amount of data that can be held by a device. Devices usually exist in only two unique states, represented by the binary digits 0 and 1. In logical terms, they can be inferred as either ‘on’ or ‘off’, or ‘true’ or ‘false’.

The implementation of bits to store and exchange data can be traced to the usage of the punched card system created by Basile Bouchon and Jean-Baptiste Falcon in 1725, for semi-automatic textile looms. Joseph Marie Jacquard created the first fully automatic loom called the Jacquard loom in 1805, which was based on the loom design by Jacques de Vaucanson. Based on the punched card system, inventors such as Charles Babbage, Semen Korsakov and Hermann Hollerith developed data storage systems for calculating and tabulating large amounts of data. In telecommunications, these principles were applied to Morse code, teletypes and stock ticker machines.

Bits can be applied in various modes. A bit in a computer or computing device, is typically denoted by an electrical voltage or current pulse, or by the electrical state of a flip-flop circuit. Devices that use positive logic, a numerical value is denoted by a positive voltage proportional to the electrical ground voltage, whereas a numerical value of 0 is denoted by 0 volts.

In computer memory such as Dynamic Random Access Memory (DRAM) or flash memory, the two values of a bit can be denoted by two stages of electric charge stored in a capacitor. In magnetic storage devices, it can be denoted by the polarity of magnetization of a specific part of a ferromagnetic film. Optical discs store bits in the form of pits and bumps on a reflective surface.

In the computing domain, bits are multiplied to denote varied units of digital information storage. The table below displays the different levels of multiples of bits and their corresponding value as determined by the International System of Units (SI).