depends on the implementation. squeak makes using C routines and libraries easy. The older commercial smalltalk's all have simple ways of making system calls

depends on the implementation. squeak makes using C routines and libraries easy. The older commercial smalltalk's all have simple ways of making system calls or writing primitives inline or as libraries. Ruby does make adding C easy. Smalltalk is a little less friendly in this regards. But only a little and that is implementation specific.