Application services are offered through a single program known officially as the Cooperative Macintosh Toolbox environment, but universally referred to as the Blue Box. The Blue Box encapsulates an existing System 7 operating system inside a single process and address space. Mac programs run inside the Blue Box much as they do under System 7, as cooperative tasks that use the non-reentrant Toolbox calls. A worst-case scenario is that an application in the Blue Box crashes, taking down the entire Blue Box instance with it. This does not result in the system as a whole going down, however, and the Blue Box can be restarted.