05 ddt

This document is the Programmer's Reference Manual for DDT-10 (Dynamic Debugging Technique), a tool developed by Digital Equipment Corporation (DEC) for the PDP-10 computer system, with copyright dates from 1968-1970.

DDT-10 is designed for on-line checkout, testing, and program composition of MACRO-10 and FORTRAN programs. It operates post-assembly or compilation, loading alongside the user's binary object program and occupying approximately 2K of core memory.

Key functionalities include:

• Setting breakpoints to suspend program execution and examine partial results.
• Examining and modifying the contents of any memory location, supporting various type-out and type-in modes (symbolic, numeric, text, floating-point, half-word, byte).
• Symbolic on-line assembly and modification, allowing insertions and deletions in source language.
• Defining and managing symbols within the debugger.
• Performing searches for specific words, non-words, or effective addresses within memory.
• Conditional debugging, including conditional breakpoints, conditional dumps, and calling user-coded debugging subroutines.
• Controlling program execution (starting, resuming, automatic restarts).
• Paper tape control for loading and saving programs (more extensively in its executive mode variant).

DDT-10 facilitates rapid and iterative debugging, allowing programmers to quickly identify bugs, make changes, and immediately re-execute corrected sections of their code. It is loaded via the Linking Loader with a /D switch and initiated with the DDT monitor command. A special version, EDDT, is available for executive mode debugging.