A high-level debugger for PL/I,Fortran and Basic

Dartmouth College has implemented a single debugger for several languages sharing a common runtime environment: PL/I, Basic and Fortran. The debugger is fairly powerful; users set breakpoints and traces which occur whenever the values of given variables change, or whenever certain relational expressions become true, for example. All debugging is carried on in a syntax similar to that of a high-level language. This debugger was implemented in about a month. It should be fairly easy to implement on most timesharing systems. This paper describes the debugger's user interface and gives a rough sketch of its implementation.