The binary conversion function has an index of 0 to 18, while the BCD conversion function uses an index of 0 to 20. The decimal range of 0 to 99,999 determines these indices.

bc, the binary calculator, ... Let's say I want to confirm a conversion I listed earlier, by converting 33 hex into decimal. This is easily done: ... and those prefaced with "0x" are hexadecimal.