Digital Research CP-M-86 for the IBM Personal Computer Version 1

Dynamic Debugging Technique (DDT) is a series of

debugger A debugger is a computer program used to test and debug other programs (the "target" programs). Common features of debuggers include the ability to run or halt the target program using breakpoints, step through code line by line, and display ...

programs originally developed for

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...

(DEC) hardware, initially known as DEC Debugging Tape because it was distributed on

paper tape Five- and eight-hole wide punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data st ...

. The name is a pun on the insecticide

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

. The first version of DDT was developed at

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

for the

PDP-1 The PDP-1 (Programmed Data Processor-1) is the first computer in Digital Equipment Corporation's PDP series and was first produced in 1959. It is known for being the most important computer in the creation of hacker culture at the Massachusetts ...

computer in 1961, but newer versions on newer platforms continued to use the same name. After being ported to other vendor's platforms and changing media, the name was changed to the less DEC-centric version. Early versions of

Digital Research Digital Research, Inc. (DR or DRI) was a privately held American software company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser ...

CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/Intel 8085, 85-based microcomputers by Gary Kildall of Digital Research, Dig ...

and

CP/M-86 CP/M-86 is a discontinued version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Re ...

kept the DEC name DDT (and DDT-86 and DDT-68K) for their debugger, however, now meaning Dynamic Debugging Tool. The CP/M DDT was later superseded by the '' Symbolic Instruction Debugger'' (SID, ZSID, SID86, and GEMSID) in

DR DOS DR-DOS is a disk operating system for IBM PC compatibles, originally developed by Gary A. Kildall's Digital Research, Inc. and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. Upon its introduction in 1988, ...

and

GEM A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. Certain rocks (such as lapis lazuli, opal, an ...

. In addition to its normal function as a debugger, DDT was also used as a top-level

command shell An operating system shell is a computer program that provides relatively broad and direct access to the system on which it runs. The term ''shell'' refers to how it is a relatively thin layer around an operating system. A shell is generally a ...

for the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...

(MIT)

Incompatible Timesharing System Incompatible Timesharing System (ITS) is a time-sharing operating system developed principally by the MIT Artificial Intelligence Laboratory, with help from Project MAC. The name is the jocular complement of the MIT Compatible Time-Sharing Syste ...

(ITS)

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

; on some more recent ITS systems, "PWORD"—which implements a restricted subset of DDT's functionality—is run first and is overlaid with DDT as soon as the user logs in. DDT could run and debug up to eight processes (called "jobs" on ITS) at a time, such as several sessions of TECO, and DDT could be run

recursively Recursion occurs when the definition of a concept or process depends on a simpler or previous version of itself. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in m ...

- that is, some or all of those jobs could themselves be DDTs (which could then run another eight jobs, and so on). These eight jobs were all given unique names, and the usual name for the original and top-most DDT was "HACTRN" ("hack-tran").

Guy L. Steele Guy Lewis Steele Jr. (; born October 2, 1954) is an American computer scientist who has played an important role in designing and documenting several computer programming languages and technical standards. Biography Steele was born in Missouri ...

wrote a

filk Filk music is a musical culture, genre, and community tied to science fiction, fantasy, and horror fandom and a type of fan labor. The genre has existed since the early 1950s and been played primarily since the mid-1970s. The genre has a ni ...

poem parody of

Edgar Allan Poe Edgar Allan Poe (; January 19, 1809 – October 7, 1849) was an American writer, poet, editor, and literary critic who is best known for his poetry and short stories, particularly his tales involving mystery and the macabre. He is widely re ...

's "

The Raven "The Raven" is a narrative poem by American writer Edgar Allan Poe. First published in January 1845, the poem is often noted for its musicality, stylized language and supernatural atmosphere. It tells of a distraught lover who is paid a visit ...

," entitled ''The HACTRN''.

DEC-10/DEC-20 DDT

DDT (Dynamic Debugging Technique), as implemented on the

DECsystem-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

DECSYSTEM-20 The DECSYSTEM-20 was a family of 36-bit Digital Equipment Corporation PDP-10 mainframe computers running the TOPS-20 operating system and was introduced in 1977. PDP-10 computers running the TOPS-10 operating system were labeled ''DECsystem ...

allowed references to symbols within the programming being debugged. This feature loaded symbols from the .EXE executable file; a special version named SDDT used symbols from the running monitor and allowed system programmers to "peek" inside.

References

External links

DDT Command List
for a freeware version written in portable C
ITS 1.5 Reference Manual
-(Artificial Intelligence Memo No. 161A)
ITS: Luser's Guide

The Great Quux Poem Collection
-(See especially the notes to the poem ''The HACTRN'') {{Digital Research Debuggers Digital Equipment Corporation CP/M Command shells

DEC-10/DEC-20 DDT

See also

References

External links