In the ancient non-electronic advice processing devices, such as Jacquard's approach or Babbage's Analytical Engine, a bit was generally stored as the position of a automated batten or gear, or the attendance or absence of a aperture at a specific point of a cardboard agenda or tape. The aboriginal electrical accessories for detached argumentation (such as elevator and cartage ablaze ascendancy circuits, blast switches, and Konrad Zuse's computer) represented $.25 as the states of electrical relays which could be either "open" or "closed". When relays were replaced by exhaustion tubes, starting in the 1940s, computer builders experimented with a array of accumulator methods, such as burden pulses traveling bottomward a mercury adjournment line, accuse stored on the central apparent of a cathode-ray tube, or blurred spots printed on bottle discs by photolithographic techniques.
In the 1950s and 1960s, these methods were abundantly supplanted by alluring accumulator accessories such as alluring amount memory, alluring tapes, drums, and disks, breadth a bit was represented by the polarity of magnetization of a assertive breadth of a ferromagnetic film, or by a change in polarity from one administration to the other. The aforementioned assumption was after acclimated in the alluring balloon anamnesis developed in the 1980s, and is still begin in assorted alluring band items such as busline tickets and some acclaim cards.
In avant-garde semiconductor memory, such as activating accidental admission anamnesis or beam memory, the two ethics of a bit may be represented by two levels of electric allegation stored in a capacitor. In programmable argumentation arrays and assertive types of read-only memory, a bit may be represented by the attendance or absence of a administering aisle at a assertive point of a circuit. In optical discs, a bit is encoded as the attendance or absence of a diminutive pit on a cogitating surface. In apparent bar codes, $.25 are encoded as the array of alternating atramentous and white lines.
In the 1950s and 1960s, these methods were abundantly supplanted by alluring accumulator accessories such as alluring amount memory, alluring tapes, drums, and disks, breadth a bit was represented by the polarity of magnetization of a assertive breadth of a ferromagnetic film, or by a change in polarity from one administration to the other. The aforementioned assumption was after acclimated in the alluring balloon anamnesis developed in the 1980s, and is still begin in assorted alluring band items such as busline tickets and some acclaim cards.
In avant-garde semiconductor memory, such as activating accidental admission anamnesis or beam memory, the two ethics of a bit may be represented by two levels of electric allegation stored in a capacitor. In programmable argumentation arrays and assertive types of read-only memory, a bit may be represented by the attendance or absence of a administering aisle at a assertive point of a circuit. In optical discs, a bit is encoded as the attendance or absence of a diminutive pit on a cogitating surface. In apparent bar codes, $.25 are encoded as the array of alternating atramentous and white lines.
No comments:
Post a Comment