I think it is possible to have single and double floating point numbers represented using the same 32-bits. Just for double, dedicate more bits to represent the exponent and that is it.

Double

*precision* usually means more precision, or more "significant digits", which is more bits in the mantissa rather than in the exponent. There's an interesting table of various FP formats here: http://home.earthlink.net/~mrob/pub/math/floatformats.html

You could theoretically expand the RANGE of a FP number by increasing either the exponent bits or exponent base (I imagine the latter has an "interesting" effect on precision...

I remember having a particularly educational experience with FP numbers back in college, trying to do my physics homework on the local mainframes in APL. Seems the PDP-10 FP format had a max/min exponent of +/-38 (as does IEEE 754 single precision, apparently), which was not at all enough to handle

hbar

^{2}. Annoying. (how may ways does this paragraph give away my age ? :-))