There's an algorithm to deal with this kind of additive small error, the Kahan Summation algorithm. It keeps a second number to record the residual of an additi

There's an algorithm to deal with this kind of additive small error, the Kahan Summation algorithm. It keeps a second number to record the residual of an addition so that adding something small to something large doesn't go awry. With modern floating point, it's rarely an issue, but with a mere 24 bits, I guess it was a terrible problem.