SmallInteger''''''s is the kindOf: Integers in Smalltalk. They typically are optimized in any decent Smalltalk implementation. SmallInteger''''''s are limited in range (as opposite to Integers, whose range is only limited by memory available).

Typical optimization is to present SmallInteger''''''s in object pointer e.g. some pointers to objects can be recognized as being SmallInteger''''''s and treated with low level host system opcodes (addition, multiplication etc). The good thing about SmallInteger''''''s is their dynamic conversion to Integers when their value goes out of range. The good thing about Smalltalk is that Integers never overflow. :) -- PavelPerikov.