A graphical approach to the tracing and debugging of
simulations is presented. First, a number of desirable features for such
a system are briefly outlined. An extension to the Simula class SIMULATION
is then described which provides these features for the application programmer.
The extension has been designed so that it is simple to use in its
default state but is also highly extensible, allowing the programmer to
obtain graphical traces quickly or to produce graphical traces of
arbitrary complexity. Examples are given illustrating both of
these facets and comparing these to a non-graphical trace of the same
program. Limitations to the approach are discussed.