I've been working with numbers in fractional form (e.g. 1/2) and written out (e.g. 0.5). However, the numbers are in binary and I do not know what to call the dot between the zero and five in the written out example. Calling it a decimal point seems to imply that I am working in base 10, but that is not true. Is there a term specific to the binary number system?
You can refer to this symbol as a radix point no matter what the base is.
In computer science and mathematics, the word radix can mean the same thing as base or root. The contemporary meaning derives from earlier meanings referring literally to the "roots" of plants, and later to roots in a mathematical sense and other senses.
The OED provides this definition:
Math. and Computing. The base of a scale of numeration or a system of logarithms
In binary, the point can also be referred to as a binary point. Here is an example use from the OED under a different headword (mantissa):
After multiplication has been completed the digit following the binary point must be examined and, if this digit is 0, a corrective shift must be applied to the mantissa together with an adjustment of the exponent.
- 1960 - M. G. Say et al. Analogue & Digital Computers v. 142
Some people have also used the term bicimal point, a portmanteau of "binary" and "decimal," to describe this symbol. Bicimal is not defined in dictionaries that I checked, but it can be found in use.
A bicimal is the base-two analog of a decimal; it has a bicimal point and bicimal places, and can be terminating or repeating.