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How magnetic substances store data?

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How magnetic substances store data?

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  1. lots of ways.  depending on the substance.

    old mainframe computers used to have  "core memory".

    that was because each bit was a small ferrite donut, which could be magnetized in either direction.

    clockwise was 0 and counter clockwise was 1.

    (or vice versa, i don't remember.)

    on a hard disk, it's like you have a sticky compass, and magnetize it in one direction or the other.

    and the needle stays, until it's changed.

    however, it's not "1" is left and "0" is right.

    maybe, at least in some cases "0" means that this bit is the same as the last, and "1" means it's different.

    in any case, you still have a ferrite surface, with drive heads creating and reading the "dots".

    to get more data, you have to make smaller dots.

    which means that you have to "fly" the read-write heads closer to the medium, so that there's less "spill over" to surrounding areas.

    the art is, how close can you "fly" the heads, and make sure they never touch the medium, which is called a "head crash" and pretty much makes the drive worthless.


  2. 2 small magnets make a bit

    2 pointing the same direction is on(1) 2 pointing deferent derections is off (0)

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