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Thread: Helph me !

  1. #1
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    Exclamation Helph me !

    Hello that I am trying to make a function to tell me how to know if a byte is powered on or not but it must be through a mask depending on the position you send

    bool estaEncendido(char byte,int pos)
    {
    //  byte = byte<<(7-pos) ;
      //byte = byte>>(pos+1);
      int mask=1;
      int result =1;
      for(pos=0; pos<8; pos++, mask <<=1)
      {
        if((byte & mask) !=0)
        {
            result = 0;
            break;
        }
        //return byte;
      }
    }

    In the main should have been as well

    System.out.print(estaEncendido(5/*000000101*/,2/*00000100*/));
    /*00000101 */
    /*00000100 &*/
    /*00000100*/This ignition

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Helph me !

    Use the AND operator (&) to test if a bit is on. The results will be zero if the bit is not on.

    Can you explain what problem you are having?
    If you need help with some code: Post a small, complete program that compiles, executes and shows the problem. Execute the program, copy its output and paste it here and explain what is wrong.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Helph me !

    I'm not sure I understand what you're asking, but consider this:

    If you AND the existing register with a value that has ONLY the desired bit set to 1, then the result will either be all zeros or the same as the value you passed. If all zeros, the bit in question was not set. If the result is the same as that passed, then the desired value is set to one.

    For example, if the status register is:

    11010100

    and I want to know if the 4th bit from the right is set, then I would AND the above with

    00001000

    to get:

    11010100
    00001000
    --------------
    00000000

    which indicates that the bit was not set.

  4. #4
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    Default Re: Helph me !

    I want to generate a mask by means of the position as you aria ? For example if you control the position 3 that I send the 00000100 in order to make a &

  5. #5
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    Default Re: Helph me !

    Are the digits in this String the positions you want: 87654321
    If those are the positions, how many bits does a value (say 1) have to be shifted left to get to position 1?
    How many to position 2? etc
    If you don't understand my answer, don't ignore it, ask a question.

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