Ralph G Selfridge <[EMAIL PROTECTED]> wrote: > > In the early days there was no floating point hardware. So all our > software had to plan for and allow a moving decimal point. So you > could have as much precision as you wanted (and in fact I had some > software for 1500 digit work), but it was gratefully given up with > the arrival of floating point hardware. Even with the loss of some > accuracy. > This does not accord with my memory or understanding. The first machines, Zuse's, only had floating point hardware. It was John von Neumann's ill-gotten idea to do without. He had 40 bit words and you had to do your own scaling. So scientists wrote their own program libraries to do automatic scaling (so-called floating point) and this eventually forced the hardware support into being outside Europe.
I remember using FORTRANSIT (the IT because it went through Carnegie Mellon's compiler) on the IBM 650. It was a decimal machine (in Australia, it had a big box added to allow it to do sterling arithmetic as well) with only integer arithmetic, but FORTRANSIT had integer and real variables. The only true floating point hardware I remember was a plug-panel calculator (the 626?) in which you could place your fraction point where you wanted it to be in the registers. Note that the automatic scaling (so-called floating point) merely extends the range of numbers you can put in a word, but actually reduces the precision because of the space taken up by the exponent. The really precise machine of my experience was the 1620, a decimal machine with variable field length. You could add or multiply thousands of digits with one machine instruction if you wanted to; it had a main store of up to 80,000 digits, though the one I used only had 60,000. The mathematicians around loved it; the Model 1 used table lookup for its arithmetic (which was digit by digit) so you could actually change the arithmetic. Sadly, the Model 2 used a hardware adder. Neville Holmes, P.O.Box 404, Mowbray 7248, Tasmania Normal e-mail: [EMAIL PROTECTED] Send instant messages to your online friends http://au.messenger.yahoo.com ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
