Entry

How do you find the number of 1 bits in an integer?

Jun 7th, 2003 17:28
Sven Glazenburg, Jean-Bernard Valentaten, Allen Kolko,

I assume you want to know how to count the bits that are set (==1) in 
an integer number.
You will have to write a function that returns the binary 
representation of the integer as a string, then you can count the bits 
that are set (the 1's in your string).
Usually integers are calculated using the two's complement (as seen 
here: http://cnx.rice.edu/content/m10808/latest/), so you will have to 
consider that in your function.
HTH,
Jean
-----------------------------------------------------------------
A simple function to count the 1 bits in a number (which does not 
handle negative numbers (the two's complement)):
<%
  function NumberOfOneBits(aNumber)
    dim number, count, bit
    number=0: count=0: bit=1
    while number<aNumber
      if (aNumber and bit)=bit then
        count = count + 1
        number = number + bit
      end if
      bit = bit * 2
    wend
    NumberOfOneBits = count
  end function
  ' Try it out:
  response.write NumberOfOneBits(255) & "<br>" 'This returns 8
  response.write NumberOfOneBits(256) & "<br>" 'This returns 1
%>
Hope this helps,
Sven Glazenburg