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[bit]Bit
A binary digit. In the computer, electronics, and communications fields, “bit” is generally understood as a shortened form of “binary digit.” In a numerical binary system, a bit is either a 0 or 1. Bits are generally used to indicate situations that can take one of two values or one of two states, for example, on and off, true or false, or yes or no. If, by convention, 1 represents a particular state, then 0 represents the other state. For example, if 1 stands for “yes,” then 0 stands for “no.”
In a computer system a bit is thought of as the basic unit of memory where, by convention, only either a 0 or 1 can be stored. In a computer memory, consecutive bits are grouped to form smaller or larger “units” of memory. Depending upon the design of the computer, units up to 64 bits long have been considered. Although there is common agreement as to the number of bits that make up a byte, for larger memory units the terminology depends entirely on the convention used by the manufacturer. In all of these units the leftmost bit is generally called the most significant bit (msb) and the rightmost the least significant bit (lsb).
Bytes and larger units can be used to represent numerical quantities. In these cases the most significant bit is used to indicate the “sign” of the value being represented. By convention a 0 in the msb represents a positive quantity; a 1 represents a negative quantity. Depending on the convention used to represent these numbers, the remaining bits may then be used to represent the numerical value. In addition to numerical quantities, bytes are used to represent characters inside a computer. These characters include all letters of the English alphabet, the digits 0 through 9, and symbols such as comma, period, right and left parentheses, spaces, and tabs. Characters can be represented using ASCII (American Standard Code for Information Interchange) or EBCDIC (Extended Binary Coded Decimal Interchange Code). The latter is used by some mainframe computers. Computers are set up to handle only one of these two character codes. Generally, the internal representation of a character is different in the two codes. For instance, in ASCII the plus sign is represented by the numerical sequence 00101011, and in EBCDIC, by 01001110.
bit
bit
(unit)The unit of information; the amount of information obtained by asking a yes-or-no question; a computational quantity that can take on one of two values, such as false and true or 0 and 1; the smallest unit of storage - sufficient to hold one bit.
A bit is said to be "set" if its value is true or 1, and "reset" or "clear" if its value is false or 0. One speaks of setting and clearing bits. To toggle or "invert" a bit is to change it, either from 0 to 1 or from 1 to 0.
The term "bit" first appeared in print in the computer-science sense in 1949, and seems to have been coined by the eminent statistician, John Tukey. Tukey records that it evolved over a lunch table as a handier alternative to "bigit" or "binit".
See also flag, trit, mode bit, byte, word.
bit
(1) (Built-In Test) See BIST.(2) (BInary digiT) The smallest element of computer storage. The bit is a single digit in a binary number containing only 0s and 1s. Physically the bit is a transistor and capacitor in a RAM cell, a magnetic domain on disk or tape, a cell in a solid state drive (SSD), a spot on optical media or a voltage pulsing through a circuit.
Transmitting Bits
Bits are used as a measurement for network transmission. For example, one hundred megabits per second (100 Mbps) means that 100 million pulses are transmitted per second. See space/time.
Storing Bytes
Eight bits make up a "byte," which is manipulated as one entity. Each byte can store one alphanumeric character, one decimal digit or a decimal number from 0 to 256 (see binary number and binary values). Measurements of files, databases, storage drives and memory (RAM) are given in bytes rather than bits. See space/time, byte and word.
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| Storage - Making it Smaller |
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| Making the spot or cell smaller increases the storage capacity. Today's storage drives hold staggering amounts of data compared to 10 years ago. For a fascinating storage technology that never became popular, see holographic storage. |
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| Storage - Making it Smaller |
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| Making the spot or cell smaller increases the storage capacity. Today's storage drives hold staggering amounts of data compared to 10 years ago. For a fascinating storage technology that never became popular, see holographic storage. |
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| Transmission - Making it Faster |
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| The bit is transmitted as a pulse of high or low voltage. Speed is increased by making the transistors open and close faster, illustrated here as a mechanical switch. Transmitting pulses within the computer is much simpler than over an external network where they are influenced by distance and interference. However, the telephone companies pioneered optical trunks, which overcame these limitations. |
Bit
part of the bridle of a horse’s harness. Bits appeared in the late Bronze Age, when the horse was first used as a beast of burden. Originally they were made of soft material (sinew) and were secured in the horse’s mouth by bone cheekpieces. Bronze bits and cheekpieces appeared at the turn of the first millennium B.C., and iron bits were prevalent in the seventh and sixth centuries B.C. Iron snaffles with movable rings at the ends were used in Rus’. In the late Middle Ages, bits were very intricate and sometimes richly ornamented. Modern bits consist of two parts and have snaffle rings.