The standard library fixed_int package is a proxy for one_word_int_guts from src/lib/std/src/one-word-int-guts.pkg which It provides core fixed-integer arithmetic capabilities.
The fixed_int package implements the Int API from src/lib/std/src/int.api.
The fixed_int package source code is in src/lib/std/fixed-int.pkg. The above information is manually maintained and may contain errors.
Int