PDP-10: Mainframe computer having a word size of 36 bits. Arguably the finest machine ever designed for assembly language programming. Discarded by its manufacturer, DEC, in favor of the VAX and VMS. Monitor: What's called the "operating system kernel" nowadays. Named in the days when what we now call a "monitor" was called a "teletype." SUPDUP: Highly sophisticated network display protocol based on the ITS terminal driver, including the Intelligent Terminal Protocol. Implemented more features with less hassle than the current day TELNET protocol. Ignored by most of the world because "it's too complicated." ITS: Incompatable Timesharing System. One of the oldest timesharing operating systems in existance, originally implemented on the PDP-6. ITS is for assembly language hackers what a Lisp Machine is for Lisp hackers. LISP: General purpose programming language, used primarily in AI work. One of the two oldest surviving general purpose programming languages (the other is FORTRAN). MIT-OZ: One of the legendary MIT PDP-10s. This one ran Twenex. Named by the person who noticed the little PDP-11/40 inside the front panel of this dinosaur: "I am Oz the great and powerful (pay no attention to the PDP-11 behind the front panel)." Hackers: People who program computers because they're there and it's fun, and who really hate to be confused with the pinheaded vandals who are properly referred to as "crackers." At MIT hackers don't just play with computers, they also play with electric trains, install working pay telephones on the roof of the Great Dome, and provide halftime entertainment at Harvard-Yale football games. LISPM (Lisp Machine): A workstation specially designed for running the Lisp programming language. PS (Public Structure): Primary filesystem on a Twenex machine. At MIT all Twenex filesystems were built on DEC RP06 removable pack disk drives; a single filesystem could span multiple disk packs. One RP06 pack held about 76000 pages of 512 36-bit words each. CHECKD: Twenex filesystem scavenger, used to diagnose and repair broken filesystems and to locate filesystem pages which had gone AWOL. ACJ: Access Control Job. Generic name for site-specific TOPS-20 security program. OZ's ACJ was particularly famous for implementing a somewhat eccentric security policy. MDDT (Monitor DDT): A version of the Twenex dialect of DDT which could examine and modify the running monitor. ("In MDDT, no one can hear you scream -- but everybody can hear you say `whoops!'" --VAF@CMU-CS-C) ANONYMOUS: Username available to anybody at all who had network access and wanted to transfer some files to or from a Twenex machine. Chaosnet: High speed (for the era) local area networking protocol suite and hardware, developed as part of the Lisp Machine project and heavily used at MIT in the early 1980s. Twenex: MIT's hacked up version of DEC's TOPS-20 operating system, which was itself a hacked up version of BBN's TENEX. At the time this story was written, all MIT Twenex machines ran on KL-10 processors. PS:LOST-PAGES.BIN.-1: Filename under which CHECKD would write out the addresses of any AWOL pages it might have found. SEND: Similar to electronic mail, but displayed directly on user's screen. Did not require one to be running a special "talk" program. Implemented by the SEND and REPLY programs, with a history kept by the system and accessable with the WHAT program. On ITS the WHAT program could also furnish useful information about bus schedules, menus at chinese resturants, and the importance of thinking before answering questions put to you by scruffy little men guarding bridges in Monty Python skits. Ann Marie Finn: Author's officemate, who really didn't deserve to be immortalized as a villain. But she does drink a lot of coffee. SIXBIT: Short for "six bit ASCII." The character set that everybody used back when even Big Blue made 36-bit machines. POPJ: PDP-10 machine instruction the right halfword of which is totally ignored and was thus occasionally used for data storage by hackers who were -really- bored. UNAME: User NAME. CD%DIR: Twenex filesystem directory attribute, indicating that the name of a particular directory was not also a Twenex username. Also called the "FILES-ONLY" bit. CLU: Programming language developed by people on the other side of the fifth floor of building NE43. CLU hackers and Lisp hackers generally regarded each other as hopelessly confused. JSYS: PDP-10 machine instruction used to implement Twenex monitor calls. ROLM DTI: Box used to interface a terminal to a ROLM data switch system which MIT received for free and spent a ridiculous amount of money installing. EDIT-20: The TOPS-20 version of SOS (Son Of Stopgap), a line oriented text editor designed to work on teletypes. Held to be particularly cretinous because it encoded five digit line numbers in a truely weird internal format for which DEC compensated by having the operating system filter out this gubbish whenever any normal program attempted to read the file. TV: The TOPS-20 version of TENEX TECO, itself a debased version of MIT (ITS) TECO. Wheel: The top level in the hierarchy of Twenex privilege bits. ("Blessed are those who run around in circles, for they shall be known as wheels.") MIT TECO: The most powerful and dangerous programming language and text editor ever invented. Implementation language for the original EMACS program, which probably could not have been implemented in an 18-bit address space without such a terse language. Has many Lisp-like features, all implemented as one character commands. Habit forming. Advanced TECO addiction has been known to cause nightmares about infinite loops four characters long. Not recomended for use via modem connections in bad weather, since at first glance many TECO programs are indistinguishable from line noise. EMACS: "Editor MACroS": Originally a set of macros (programs) written in the MIT TECO programming language. Eventually became an editor in its own right, implemented on a wide variety of machines. SPR: Software Problem Report. GALAXY: A TOPS-10/TOPS-20 macro library and associated support code. Essentially a private programming language built on top of the DEC assembler. Claimed by its fans to be a fun programming environment, the only trouble being that it defined so many macros that it was something of a challenge to keep a machine running long enough to assemble a program. Filename completion: Something that VMS, as far as the author knows, still lacks, presumably on the theory that by the time one has finished typing the entirety of a VMS command line, having to type a dozen or so extra characters won't make an appreciable difference. DDT: PDP-10 assembly language debugger. Reached its fullest flower on ITS, where it was also the default system command processor, which should give the reader some idea of why hackers loved ITS and everybody else thought it was Just Too Weird. In all known dialects of DDT, hitting the key deposits the "current value" into the "current location," which can have interesting effects when the program being debugged is, say, the running monitor.