The Standard ML Basis Library is a collection of modules providing a basic collection of abstract types that are shared by all implementations of Standard ML.  All of the primitive types of Standard ML are defined in structures in the Standard Basis.  It also defines a variety of other commonly-used abstract types.  Please see the Standard ML Basis Library for a complete description of the Standard Basis.

Most implementations of Standard ML include module libraries implementing a wide variety of services.  These libraries are usually not portable across implementations, particularly not those that are concerned with the internals of the compiler or its interaction with the host computer system.  Please refer to the documentation of your compiler for information on its libraries.