The answer is yes, the mantissa bit goes to exponentially. They are called abnormal (AKA denormal) numbers. For example, with IEEE double precision, the smallest power of two exponents for a normal number is a number with a full 53 bit precision - 2 -1022 . But two degrees can be represented up to 2-1074 which are determined by the location of the first 1 bit in an abnormal value. Thus, an indicator 2-1023 has 52 bits of accuracy, 2-1024 has 51 bits of precision, ..., 2-1074 has 1 bit of accuracy.
(See my article, What powers of two look inside a computer to visualize this better.)
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