SID is a framework for building computer system simulations. Specifically, a simulation is comprised of a collection of loosely coupled components. Simulated systems may range from a CPU's instruction set to a large multi-processor embedded system.

SID defines a small component interface which serves to tightly encapsulate them. Components may be written in C++, C, Tcl or any other language to which the API is bound. Typically, components are separately compiled and packaged into shared libraries. A standard run-time linking/loading interface is defined for these.

The package includes a growing library of components for modeling hardware and software parts, instrumentation, control, and external interfaces.