The COSC-1 Assembly Language Simulator running on the Micro Network was developed as a tool for teaching the basics of computer structure and assembly language programming. COSC-1 fs a simple computer of complexity about equivalent to a small personal computer. There is no actual hardware that behaves like a COSC-1 computer, instead its behavior is simulated on another computer. While this is somewhat unreal, it has the advantage that the Micro Network provides quite a sophisticated programming environment to make life easier for the users. Another advantage is that some of the awkward features of real machines have been left out so that simple programs are more straightforward to write and understand. The network also provides file storage. The COSC-1 Simulator allows assembly-language programs to be entered, assembled and debugged interactively on the IBM Personal Computer workstations used with the Micro Network. There is an editor for preparing COSC-1 programs and facilities for translating these into machine language and running them. In addition, it is possible to start and stop a COSC-1 program and peep into a COSC-1 machine to study what happens at each step while a program is running.