DDT

DDT was also widely used -- in fact badly over-used -- as an agricultural pesticide, and began to accumulate in rivers, soils and animal tissues. Rachel Carson's 1962 blockbuster Silent Spring linked DDT to falling raptor and songbird populations. Her evidence has since been challenged, but the damage was done: there was a massive public backlash against DDT and it was outlawed for use in most developed nations by the mid-1970s. DDT is now popularly believed to be extremely toxic to both humans and animals and has been implicated in particular in breast cancer and the feminising of fish, reptiles and perhaps mammals. In fact, the studies have been contradictory and there is no clear evidence that DDT, even with long-term exposure, has significant negative effects on human health.

DDT has, nevertheless, been characterised as a persistent organic pollutant (other POPs include chlordane, dieldrin and polychlorinated biphenyls) and there is currently a campaign, led by the World Wildlife Fund and others, to ban its use globally.

The proposed United Nations treaty on POPs is facing significant opposition, however, because DDT remains for many developing nations the single most effective and cheapest weapon in the war against malaria.

Malaria is one of the world's deadliest diseases. There are 300-500 million cases each year, 90% of them in Africa, and these result in two and a half million deaths annually, mostly of children. It was the leading cause of death in sub-Saharan Africa until it was recently overtaken by AIDS. The incidence was dramatically reduced by the use of DDT, and has been rising steadily wherever DDT use has been stopped.

Nations which need DDT for malaria control are not obliged to sign up to a global ban, but they have little room to act independently: DDT production facilities have been shut down everywhere but in India and China, with the result that it is now more difficult and expensive to obtain. Donors, under pressure from environmental groups in the richer nations, have also in some cases forbidden the use of DDT as a condition for receiving aid. This paradoxically condemns the populations of countries like Mozambique to further ill-health and poverty -- sick people make bad workers, and foreign investors are understandably reluctant to expose themselves to a disease which carries a significant risk of permanently damaged health or death. DDT seems the lesser of two evils.

Adam Bernard (adamb@bgumail.bgu.ac.il)

DDT /D-D-T/ n.

[from the insecticide para-dichloro-diphenyl-trichloroethene] 1. Generic term for a program that assists in debugging other programs by showing individual machine instructions in a readable symbolic form and letting the user change them. In this sense the term DDT is now archaic, having been widely displaced by `debugger' or names of individual programs like adb, sdb, dbx, or gdb. 2. [ITS] Under MIT's fabled ITS operating system, DDT (running under the alias HACTRN, a six-letterism for `Hack Translator') was also used as the shell or top level command language used to execute other programs. 3. Any one of several specific DDTs (sense 1) supported on early DEC hardware and CP/M. The PDP-10 Reference Handbook (1969) contained a footnote on the first page of the documentation for DDT that illuminates the origin of the term:

Historical footnote: DDT was developed at MIT for the PDP-1 computer in 1961. At that time DDT stood for "DEC Debugging Tape". Since then, the idea of an on-line debugging program has propagated throughout the computer industry. DDT programs are now available for all DEC computers. Since media other than tape are now frequently used, the more descriptive name "Dynamic Debugging Technique" has been adopted, retaining the DDT abbreviation. Confusion between DDT-10 and another well known pesticide, dichloro-diphenyl-trichloroethane (C14-H9-Cl5) should be minimal since each attacks a different, and apparently mutually exclusive, class of bugs.

(The `tape' referred to was, incidentally, not magnetic but paper.) Sadly, this quotation was removed from later editions of the handbook after the suits took over and DEC became much more `businesslike'.

The history above is known to many old-time hackers. But there's more: Peter Samson, compiler of the original TMRC lexicon, reports that he named `DDT' after a similar tool on the TX-0 computer, the direct ancestor of the PDP-1 built at MIT's Lincoln Lab in 1957. The debugger on that ground-breaking machine (the first transistorized computer) rejoiced in the name FLIT (FLexowriter Interrogation Tape).

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.