:PDP-10: [Programmed Data Processor model 10] n. The machine that made timesharing real. It looms large in hacker folklore because of its adoption in the mid-1970s by many university computing facilities and research labs, including the MIT AI Lab, Stanford, and CMU. Some aspects of the instruction set (most notably the bit-field instructions) are still considered unsurpassed. The 10 was eventually eclipsed by the VAX machines (descendants of the PDP-11) when DEC recognized that the 10 and VAX product lines were competing with each other and decided to concentrate its software development effort on the more profitable VAX. The machine was finally dropped from DEC's line in 1983, following the failure of the Jupiter Project at DEC to build a viable new model. (Some attempts by other companies to market clones came to nothing; see {Foonly}) This event spelled the doom of {{ITS}} and the technical cultures that had spawned the original Jargon File, but by mid-1991 it had become something of a badge of honorable old-timerhood among hackers to have cut one's teeth on a PDP-10. See {{TOPS-10}}, {{ITS}}, {AOS}, {BLT}, {DDT}, {DPB}, {EXCH}, {HAKMEM}, {JFCL}, {LDB}, {pop}, {push}, {appendix A}.

:PDP-20: n. The most famous computer that never was. {PDP-10} computers running the {{TOPS-10}} operating system were labeled `DECsystem-10' as a way of differentiating them from the PDP-11. Later on, those systems running {TOPS-20} were labeled `DECSYSTEM-20' (the block capitals being the result of a lawsuit brought against DEC by Singer, which once made a computer called `system-10'), but contrary to popular lore there was never a `PDP-20'; the only difference between a 10 and a 20 was the operating system and the color of the paint. Most (but not all) machines sold to run TOPS-10 were painted `Basil Blue', whereas most TOPS-20 machines were painted `Chinese Red' (often mistakenly called orange).

:peek: n.,vt. (and {poke}) The commands in most microcomputer BASICs for directly accessing memory contents at an absolute address; often extended to mean the corresponding constructs in any {HLL} (peek reads memory, poke modifies it). Much hacking on small, non-MMU micros consists of `peek'ing around memory, more or less at random, to find the location where the system keeps interesting stuff. Long (and variably accurate) lists of such addresses for various computers circulate (see {{interrupt list, the}}). The results of `poke's at these addresses may be highly useful, mildly amusing, useless but neat, or (most likely) total {lossage} (see {killer poke}).

Since a {real operating system} provides useful, higher-level services for the tasks commonly performed with peeks and pokes on micros, and real languages tend not to encourage low-level memory groveling, a question like "How do I do a peek in C?" is diagnostic of the {newbie}. (Of course, OS kernels often have to do exactly this; a real C hacker would unhesitatingly, if unportably, assign an absolute address to a pointer variable and indirect through it.)

:pencil and paper: n. An archaic information storage and transmission device that works by depositing smears of graphite on bleached wood pulp. More recent developments in paper-based technology include improved `write-once' update devices which use tiny rolling heads similar to mouse balls to deposit colored pigment. All these devices require an operator skilled at so-called `handwriting' technique. These technologies are ubiquitous outside hackerdom, but nearly forgotten inside it. Most hackers had terrible handwriting to begin with, and years of keyboarding tend to have encouraged it to degrade further. Perhaps for this reason, hackers deprecate pencil-and-paper technology and often resist using it in any but the most trivial contexts. See also {appendix B}.

:peon: n. A person with no special ({root} or {wheel}) privileges on a computer system. "I can't create an account on *foovax* for you; I'm only a peon there."

:percent-S: /per-sent' es'/ [From the code in C's `printf(3)'
library function used to insert an arbitrary string argument] n. An
unspecified person or object. "I was just talking to some
percent-s in administration." Compare {random}.

:perf: /perf/ n. See {chad} (sense 1). The term `perfory'
/per'f*-ree/ is also heard. The term {perf} may also refer to
the preforations themselves, rather than the chad they produce when
torn.

:perfect programmer syndrome: n. Arrogance; the egotistical conviction that one is above normal human error. Most frequently found among programmers of some native ability but relatively little experience (especially new graduates; their perceptions may be distorted by a history of excellent performance at solving {toy problem}s). "Of course my program is correct, there is no need to test it." "Yes, I can see there may be a problem here, but *I'll* never type `rm -r /' while in {root}."

:Perl: /perl/ [Practical Extraction and Report Language, a.k.a Pathologically Eclectic Rubbish Lister] n. An interpreted language developed by Larry Wall <lwall@jpl.nasa.gov>, author of `patch(1)' and `rn(1)') and distributed over USENET. Superficially resembles `awk(1)', but is much hairier (see {awk}). UNIX sysadmins, who are almost always incorrigible hackers, increasingly consider it one of the {languages of choice}. Perl has been described, in a parody of a famous remark about `lex(1)', as the "Swiss-Army chainsaw" of UNIX programming.