10E500?

[debrouxl]

BCD floats are much better than binary floats at avoiding rounding errors, the likes of e.g. 24 being printed as 23.999999999999 or so. The major FPU-less CPUs from the 80s, maybe from even earlier, have support for BCD arithmetic. Binary floats are faster, however.

Advanced Mathematics Software in the TI-68k series uses a custom 10-byte format for floating-point values:
* 1 bit for sign;
* 1 bit for exponent sign;
* 14 bits (binary) for exponent;
* 64 bits (BCD) for mantissa.
In principe, this allows usage of 16 digits and exponents up to -16384/+16383. However, only some low-level BCD arithmetics functions support that extended range; many higher-level functions use overflow to infinity for exponents outside the -999/+999 range, and round to 14 or 12 digits.