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On a calculator, pressing = more than once

  1. Dec 14, 2014 #1
    In calculator, when we press = more than one times, why answer will get change?
    yesterday, i pressed 1+1 then i press = it gives 2, again i press = it gives 3, why if answer is 2 why it is showing 3, all calculators like this showing, is this manufacturing error?
  2. jcsd
  3. Dec 14, 2014 #2


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    Well, my calculators don't do that, but what my calculator does do is that it has an ans button (short for previous answer), so if you press
    1 =
    then 1 appears as the answer, then press
    ans + 1 =
    then 2 appears, now just press = again, then 3 appears, etc. because ans is updated as you go along. This makes for easily applying recursive equations, such as quickly finding a good approximation to a root of a function using Newton's method.

    Maybe this is what your calculator is doing? Can you try
    and post the results for all of these?
  4. Dec 14, 2014 #3


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    It's applying a recursive operation, as Mentallic said.

    In the "classic" Casio calculators (don't know how the new ones are designed), simply pressing "=" repeatedly wouldn't do the job. Instead you needed to press the operation key, e.g. "+" or "X" twice in succession. Then a "K" symbol would appear on the display, signifying entry into "constant" mode. In this state, repeatedly pressing "=" would recursively apply the required operation.

    E.g. To recursively add two to various inputs you would do:

    2 + +

    and a "K" symbol would appear.

    Now to just count in twos, you would keep pressing "=" to get "4, 6, 8..." ad infinitum.

    To add two to a different input you can key it in, then press "=", e.g.

    103 =

    which would yield 105.

    I guess the modern calculators don't need you to explicitly enter K mode. But I consider the "old-fashioned" mode of operation more robust by far because it's fairly easy to mistakenly double-press "=" and if you might've unwittingly applied an operation twice without actually meaning to.
  5. Dec 14, 2014 #4
    @Curious3141 i think you didn't understand my question, why is answer is changing due it is manufacturing error or not?
  6. Dec 14, 2014 #5


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    I don't think you understood his answer.

    And if you cared to actually digest what has been written (if you have read much of it at all) then you'd notice that for us to help you further, since we don't know what calculator you're using - and it should be evident by now that many calculators work differently, then doing this might help:

    And no, it's very unlikely to be a manufacturing error. It's more of a software design feature that the developers decided to go with.
  7. Dec 15, 2014 #6
    It's not an error. Pressing equals repeats the operation on the currently displayed result. e.g. 42+1 = 43 ... press equals again and you'll get 43+1 = 44.
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