Thread provides synchronization primitives for multiple threads of control. Word provides operations on unsigned words. Implementations are free to extend the required interfaces, provided they do not invalidate clients of the unextended interfaces. SRC Modula-3 provides many other interfaces. Fmt and Lex provide for textual formatting and scanning of numbers and other data.
Table provides generic hash tables.
The full set of library interfaces distributed with SRC Modula-3 is available here.