Problem with calculation

Hi

I have tried to use float point but I get zero...

     int delay;
     float Temp;


      for(delay=82; delay < 920; delay += 20)
        {
                Temp= (delay-82)/(920-82);
                Temp = 680 * Temp;

                printf("result is %f\n", Temp);
        }

Hi

I have tried to use float point but I get zero...

     int delay;
     float Temp;


      for(delay=82; delay < 920; delay += 20)
        {
                Temp= (delay-82)/(920-82);
                Temp = 680 * Temp;

                printf("result is %f\n", Temp);
        }

'delay' is an int, the RHS expression (delay-82)/(920-82) yields 0 for any value of 'delay' less than 920. 0 is converted to 0.0 for assignment to 'Temp'. 680 * 0.0 = 0.0.

Try:

Temp= ((float)delay-82)/(920-82);

Scaling fixed point math takes some understanding. Perhaps you could start by reviewing this article or Google for fixed point math: http://www.wwnet.net/~stevelim/fixed.html

Perhaps you should also review a "C" tutorial. If you want to perform floating point operations then you need to have your equation representative of a floating point calculation.

So as Dan has suggested "cast" the divide operation or change your constants to be float values.

  for(delay=82; delay < 920; delay += 20) {
    Temp = (delay-82.0)/(920.0-82.0);
    Temp = 680.0 * Temp;
    printf("result is %f\n", Temp);
  }