This is a modified version of the 4.2BSD debugger dbx. It is intended to be able to handle Modula-2, Pascal, C and Fortran. The source is written in C, with interface files (names ending in ".h") automatically generated from implementation files (names ending in ".c") so they (the ".h" files) should NOT be modified. The subdirectory "tests" contains some test cases for Modula-2, C, and Pascal. These tests should be run successfully before installing dbx. Makefile contains the relevant information for building, testing, and installing dbx. Running "make" will build dbx, "make test" will test it, and "make install" will install it after first checking to make sure it has passed all the available tests. Please reports problems, comments, and suggestions to: Mark Linton Computer Systems Laboratory Stanford University ARPA: linton@su-shasta UUCP: Shasta!linton or ucbvax!linton