Significant digits in a float?

[Roy Smith]

In article <ljsghc$65b$1 at speranza.aioe.org>,
 Mark H Harris <harrismh777 at gmail.com> wrote:

>     Absolutely, snort.  I still have my K&E (Keuffel & Esser Co. N.Y.); 
> made of wood... (when ships were wood, and men were steel, and sheep ran 
> scared) ... to get to the S L T scales I have to pull the slide out 
> (turn it over) and reinsert it. You're right, the CF and DF scales are 
> missing, but the A B scales have the π symbol where it should be (more 
> or less).  Mine is the 4058 C model, and you're right... has maths 
> equivalents and conversions printed on the back...

For those who have no idea what we're talking about, take a look at 
http://www.ted.com/talks/clifford_stoll_on_everything.  If you just want 
to see what you do with a slide rule, fast forward to 14:20, but you 
really owe it to yourself to invest the 18 minutes to watch the whole 
thing.