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.
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 h
. Annoying. (how may ways does this paragraph give away my age ? :-))