From: Chris <behmc@...>

Date: Tue, 18 Nov 1997 19:06:19 -0500

Date: Tue, 18 Nov 1997 19:06:19 -0500

>On 11/18/97 9:11 AM, Chris <behmc@...> said: > >>Can someone give me the basics of binary addition and subtraction? I think >>I understand (and can do) binary addition, but subtraction is giving me >>fits. >> >>Thanks, >>*Chris > >OK. > >It is just like subtraction in decimal. > > 26 >-17 >--- > 9 > >Each digit has a "weight." In decimal it is powers of ten: > > 1000s 100s 10s 1s >or 10 to the 3rd, 10 to the 2nd, 10 to the 1st, and 10 to the zero. > >It goes on in each direction ad infinitum. > >The same is true for all numbering systems, binary, octal, hexadecimal, >base-12 and so on. > > 11010 > -10001 >------- > 1001 > >Binary: > > 32s 16s 8s 4s 2s > 1s >or 2 to the 5th, 2 to the 4th, 2 to the 3rd, 2 to the 2nd, 2 to the 1st, >and 2 to the zero. > >So in the example above we have a "2 to the zero" subtracted from a null, >so we have to borrow a >"2 to the 1st," or a value of two from the next digit, subtract the "2 to >the 1st" (a one), leaving us with a value of 1 for the 2 to the zero >column. > >We borrowed that 2 to the 1st digit so it is now zero. > >We move to the left and find a zero in the 2 to the 2nd columns. > >In the two to the 3rd column we subtract 0 from 1 leaving a one in that >column in the result. > >Move on to the 2 to the 4th column, subtract 1 from one, result is zero, >and we're done. > >The same principles apply to all numbering systems. > >Peace, >Caryn Roberts THANK YOU! That's exactly what I was looking for. What eluded me was the idea that each place was "greater" then 1 (unless it was the first colum). A holdover from years of decimal math caused it. Now it makes _much_ more sense. Again, thanks, *Chris