While contemporary implementations are most commonly tailored to use (UNSIGNED-BYTE 8), (UNSIGNED-BYTE 16), (UNSIGNED-BYTE 32), and (UNSIGNED-BYTE 64) along with their signed counterparts, our language allows one to freely specify and use integer types such as (UNSIGNED-BYTE 53) that could - in theory - be optimized for on architectures that use unique, by today's standards, word sizes.
This also comes from the fact that Common Lisp was specified during times that had no real standardized word sizes, and so the standard had to accomodate for different machine types on which a byte could mean different and mutually exclusive things.
While contemporary implementations are most commonly tailored to use (UNSIGNED-BYTE 8), (UNSIGNED-BYTE 16), (UNSIGNED-BYTE 32), and (UNSIGNED-BYTE 64) along with their signed counterparts, our language allows one to freely specify and use integer types such as (UNSIGNED-BYTE 53) that could - in theory - be optimized for on architectures that use unique, by today's standards, word sizes.
This also comes from the fact that Common Lisp was specified during times that had no real standardized word sizes, and so the standard had to accomodate for different machine types on which a byte could mean different and mutually exclusive things.