packet
A chunk of information transmitted over a packet switching network. Each packet usually contains destination address info as well as the main info. TCP/IP calls its packets datagrams. Cell relay calls its packets cells. Frame relay calls its packets frames.
packet switching
The protocol of dividing info into packets and sending them out, usually over a dial up line. Each packet may follow different routes and take different amounts of time to get to the destination, but in the end, all the packets are combined to form the original info. Packet switching is utilized by WAN protocols such as TCP/IP, X.25, frame relay, and cell relay.
 
In contrast to packet switching, circuit switching forms a dedicated line for real time data like audio and video. ATM (asynchronous transfer mode) tries to utilize both types of switching.
page fault
An interrupt which occurs when requested data cannot be found in current RAM. The data may have been moved from the program's working set, i.e. the data the process is actively using. If so, then usually there is either a soft page fault (data is moved to elsewhere in the physical RAM) or a hard page fault (data is moved to virtual memory, i.e. the hard drive). If the data cannot be found elsewhere then the page fault is upgraded to an invalid page fault or page fault error.
page file
See virtual memory.
PAL
Phase Alternate Line. A composite video signal popular in Europe. It has a rate of 25 frames per second, with 625 lines per frame and a power frequency of 50 Hz.. PAL uses RCA or Phono plugs. PAL-M is a variation used in Brazil with a rate of 30 frames per second. See also NTSC and TV.
Palm Computing
The maker of the Palm Pilot and the Palm OS (Operating System). These are little hand held devices that started out as PIMs (Personal Information Managers) but have branched out to incorporate mobile phone and web appliance technology.
PAP
Printer Access Protocol. Protocol in handling the users' access to printers on a network.
parallel port
A plug or interface in a computer system that transmits data several bits at a time, i.e. in parallel: side by side. This is in contrast to a serial port which transmits data one bit at a time, i.e. in series: one after another. A common parallel port is the DB-25 (25 pin D-Type connector). The Centronics port is a wide strip with slots on both sides, and is the original parallel port. A newer common parallel port is the EPP (Enhanced Parallel Port) or ECP (Extended Capabilities Port). Epson's EPP is not only backwards compatible with the Centronics but is bi-directional and can transfer data ten times as fast.
parity
A mathematical method of verifying data integrity.
parse
To take code or data and pick it apart for lexical analysis and semantic parsing. Lexical analysis takes the source and breaks it into smaller components (the smallest of which is a token). Semantic parsing derives meaning and uses the pieces. EG1: HTML code is parsed by a browser for the user to see. EG2: Source code is parsed by a compiler into object code.
Part 68
Rules and Regulations of the Federal Communications Commission, Part 68: Connection of Terminal Equipment to the Telephone Network. Technical specifications set by the FCC in 1977. It allowed 3rd party manufacturers to make devices that could physically connect to the telephone network, which, prior to Part 68, was the exclusive right of the telephone company. Even today, nearly any device directly attached to the phone line will have a Part 68 conformity sticker.
partition
A portion of a hard disk that is regarded as separate from other partitions on the same hard disk, almost as if the partitions were separate devices. Great for running multiple OSes on one machine!
password
A set of characters chosen by the user to gain entry into certain networks or programs. It is usually used in conjunction with a shorter username. Usernames and password are probably the main form of security on networks.
path
A description of the location of a file using conventions. There are several conventions:
  Name Syntax EG
Network and OS Related Physical share:\dirPath\file C:\InetPub\A\Index.htm
UNC (Uniform Naming Convention) \\server\share\dirPath\file \\WebServer\c$\InetPub\A\Index.htm
Web Related Absolute scheme://host.domain.tld:port/Dirpath/file http://www.MySite.com:80/A/Index.htm
Relative Names file relative to current directory. Starts with a directory name or file name. ../ indicates the parent directory. A/Index.htm

../Index.htm
Virtual Names file relative to the virtual home directory. Starts with /. /A/Index.htm
PBX
Private Branch eXchange. A private telephone network within an enterprise. Everyone can dial each other by dialing each other's extension. The users share a fixed number of outside lines if they need to go outside of the PBX. This is cheaper than making every phone in the network have its own connection to the local telco. See also centrex.
PC
(1) Personal Computer. Usually a computer whose main operating system is DOS or Windows various versions. PCs are not to be confused with Power PCs which are Mac computers. There are Server PCs, Workstation/Client/User PCs, Desktop PCs, Laptop PCs, Palmtop PCs (aka HPCs or Handheld PCs), and Net PCs.
 
(2) Pica. A unit of measurement common in page layout.
     1 in =     6 pc =   72 pt = 1440 twip
   1/6 in =     1 pc =   12 pt =  240 twip
  1/72 in =  1/12 pc =    1 pt =   20 twip
1/1440 in = 1/240 pc = 1/20 pt =    1 twip 
PC Card
Credit card size peripherals for portable computers. Originally came in three types, each with 68 pins: Type I (3.3 mm thick), Type II (5.0 mm), and Type III (10.5 mm). These are under the jurisdiction of the PCMCIA. Newer smaller ones are out that have only 50 pins.
PCI
Peripheral Component Interface. A 64 bit standard local bus developed by Intel. The PCI slots in the back of many computers can be used to expand the computer's capabilities. EG: You can add communications and networking communications capabilities, increase processing power, or improve graphics and video performance. The internal slot is approximately 3.5 inches. PCI runs at 33 or 66 MHz resulting in 133 or 266 Mb/s. The other popular buses include the 16 bit ISA and 32 bit EISA. See also AGP.
PCMCIA
Personal Computer Memory Card International Association. The standard for PC cards.
PD
Phase change Disk. A disk format by Panasonic that utilizes phase change technology. PDs can be written as well as read by PD drives. PDs drives can also read CD-ROM, CD-R, and CD-RW. See also removable storage.
PDC
Primary Domain Controller. See domain controller.
PDF
Portable Document Format. A graphic file format that is can be viewed across platforms via Acrobat Reader.
PDL
Program Design Language. Aka pseudo code. Writing out the general workings of a program in a non-actual programming language that is more like regular English.
peering
In the Internet, one vendor allowing another vendor to access his network. This occurs at NAPs between the big vendors, the backbone ISPs.
peer-to-peer based network
A small network where each computer can be a server or client for other computers on the network, instead of relying on a small number of dedicated servers that provide service to a larger number of clients. As a peer-to-peer network grows it would be cheaper to convert to a server based network.
peltier cooler
A peltier cooler uses an electrically powered peltier element as a heat pump in computers. The peltier element uses the Peltier Effect which is basically that when you send an electric current through two dissimilar metals connected at two points, one point becomes warm while the other becomes cool. The net effect generates more heat so a fan is definitely needed to blow that heat elsewhere. A peltier uses a lot of power so do not have it share a line with sensitive systems. Watch for humidity and condensation with peltier coolers as well.
Peripheral
Any device connected to the computer system. EGs: printers and keyboards.
Peripheral Component Interface
See PCI.
PERL
.pl. Practical Extraction and Report Language. Pathologically Eclectic Rubbish Lister. A high level programming language that was developed in 1986 by Larry Wall for UNIX programmers. PERL is a scripting language but the PERL interpreter actually compiles the script and executes it without making an executable file.
 
PERL 5 is also actually an object oriented language. It is designed to manipulate text, files, and processes and is very popular for CGIs which are essential for interactive as opposed to static web pages. PERL in all caps usually refers to the language and PERL in all small letters usually refers to the interpreter but many people use PERL with a capital letter, this is rather odd since it originated on UNIX which is case sensitive!
Permanent Virtual Circuit
PVC. See virtual circuit.
persistent
Stored in storage memory as opposed to stored in working memory.
Personal Computer
See PC.
PGML
Precision Graphics Markup Language. An Adobe proposed W3C standard for vector images for the Web. PGML would be ASCII based whereas its competitive format, Macromedia's Flash, is in binary format. See also VML.
PGP
Pretty Good Privacy. An organization developed by Philip Zimmerman that utilizes public key encryption. The PGP encryption package is free and can be used to encrypt messages. The official PGP repository is at MIT. PGP encryption is so good that the US almost made it illegal and others countries still consider it illegal.
PH
Pointy Haired. Having qualities like the Pointy Haired Boss in the Dilbert comic strip created by Scott Adams. Typically PH prefixes any idiotic  individual, eg PHB (Pointy Haired Boss) or PHManager.
pharming
Fraudulent redirecting of users from where they want to go to someplace else.
Phase Alternate Line
See PAL.
Phase change Disk
See PD.
phish
The act of using deception to acquire personal sensitive information such as passwords or credit card numbers.
phonetic alphabet

Aka International Phonetic Alphabet but that is a misnomer since the real IPA is used by linguists to phonetically describe spoken languages. A translation of an alphabet, numbers, and sometimes frequent words into clear and unmistakable words of the language. This is especially used for error free spelling out of information over the radio or telephone. Of course, different languages, countries, radio stations, military branches, police stations, emergency services, and other organizations may have their own variation. And of course it varies with time period too.

The English alphabet is A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. The NATO phonetic equivalent is Alpha Bravo Charlie Delta Echo Foxtrot Golf Hotel India Juliet Kilo Lima Mike November Oscar Papa Quebec Romeo Sierra Tango Uniform Victor Whiskey Xray Yankee Zulu. (You may see variations such as Alfa, Oskar, Viktor, and/or X-ray.) The numbers in English are 0 1 2 3 4 5 6 7 8 9. The phonetic equivalents are Zero One Two Tree Fower Fife Six Seven Eight Niner. (You may see variations such as Wun, Too, and Ait.)

Here are common phonetic alphabets common for several languages:

  • French: Anatole Berthe Célestin Désirè Eugéne Françis Gaston Henri Irma Joseph Klb'ber Louis Marcel Nicolas Oscar Pierre Quintal Raoul Suzanne Thérèse Ursule Victor William Xavier Yvonne Zoé
  • German: Anton Berta Cäsar Dora Emil Friedrich Gustav Heinrich Ida Julius Kaufmann Ludwig Marha Nordpol Otto Paula Quelle Richard Samuel Thodor Ulrich Viktor Wilhelm Xanthippe Ypsilon Zacharias
  • Spanish: Antonio Barcelona Carmen Chocolate Dolores Enrique Francia Gerona Historia Intalia José Kilo Lorenzo Llobregat Madrid Navarra Ñoño Oviedo París Querido Ramó Sáado Tarragona Ulises Valencia Washington Xilófono Yegua Zaragoza.
  • Italian: Anocna Bari Catania Domodossola Empoli Firenze Genova Hotel Imola Livorno Milano Napoli Otranto Palermo Quarto Roma Sassari Torino Udine Venezia.
  • Russian: Anna Boris Viktor Grigoriy Dmitriy Elena Yolka Zhenya Zoya Irina Yod Konstantin Liza Mariya Natasha Ol'ga Pyotr Ruslan Semyon Tat'yana Ukraina Fyodor Khar'kov Tsaritsh Chekhov Shura Shchuka Erik Yuriy Yana.
  • Romanized Mandarin: Aiya Boli Ciqi Desheng Egu Fuzhuang Geming Heping I: Yifu J.. Keren Leguan Mofan Nali Ouyang Polang Q.. Riquang Sixiang Tebie U: Weida V: Wudao W: Wuzhuang X.. Yisheng.
PHP
Personal Home Page Tools. .php, .php3, or .phtml. Linux equivalent of Microsoft's ASP (Active Server Pages). PHP script has c or PERL like syntax. PHP was created in 1994 by Rasmus Lerdorf; later major contributors include Zeev Suraski and Andi Gutmans.
Physical Unit
See PU.
pica
See pc.
picoJava
An inexpensive RISC microprocessor customized to run Java with out the need of an interpreter or JIT compiler. Since picoJava can execute the Java Virtual Machine instruction set directly, it can run Java programs that are one third smaller but 5-20 times faster. It does not have any memory or I/O interface logic, rather that would be part of the program.

picoJava is intended to be used on small or mobile devices such as cell phones, network computers, pagers, hand-held PCs, and peripherals.
pict
.pic or .pict. A graphic file format native to the Mac. It is a bitmapped image accessible by any Mac application. Pict was 1 bit color with sizes up to 32 kb. Pict 2 is 24 bit. To use on a PC, first convert to .gif.
PING
Packet INternet Groper. A trace route program that checks to see if a system is accessible. It usually sends out a signal to a target IP address and looks for a response. It is common to initially test by entering ping 127.0.0.1 at the command line, this will test the to see if the local host is properly configured with TCP/IP. The next step would be to ping an IP address of another device on your local network segment, eg if your machine is 190.150.0.50, then try 190.150.0.51 or 190.150.0.52. Next try your local subnet's router, then try IP addresses beyond your router.
ping of death
A PING packet that has been illegally set above 65,536, the largest legal size for a ping. Such a ping can crash a system's TCP/IP stack and cause a system to hang.
pipe
|. To relay or transfer the results of one action to another. EG1: expression_a | expression_b. EG2: dir | sort might be used to get a directory listing and then sort it before displaying the results in DOS. It may be said that TCP/IP is the pipe of the Internet or that SQL is the pipe for distributed databases.
pixel
The smallest unit in a computer image, it can have only one color as produced by the combination color channels feeding into it. A typical image has 72 pixels per inch. If the image is enlarged then the pixel may appear as blocks of a single color.
pixels per inch
See ppi.
PKUnzip
A standard DOS that compresses/decompresses files into or from .zip files.
plain TeX
See TeX.
platform
The general hardware and software of a computer system. Examples might be Window NT on a Pentium II, or UNIX on an Ethernet network, or Mac OS on a G3. Software must be compatible with the platform otherwise it won't work. With the ubiquity of the Internet, it has become important to be cross-platform.
PLD
Programmable Logic Device. An integrated circuit that can be programmed to perform functions via manipulating its array of AND and OR gates. PLDs include PROMs (Programmable Read Only Memory), PLAs (Programmable Logic Array), and PAL/GAL (Programmable Array Logic/Generic Array Logic).
PLSQL
PL/SQL = Procedural Language extensions to SQL. A flavor of SQL for Oracle databases that extends SQL by adding constructs similar to those found is some procedural languages.
plug-in
A piece of component software that adds functionality to a program. EG: Many image editing programs use plug-ins to do different tasks such as scan or create special effects.
PNG
.png. Portable Network Graphics. A bit-mapped graphic format that is supposed to replace GIF because PNG does not use LZW, a patented data compression algorithm. PNG saves images in 8 bit (grayscale or 256 colors) or 24 bit (true color at 16.7 million colors). In 8 b images, PNG supports transparency by designating one color, the one in the upper left hand corner, to be transparent, i.e. the color will change to the background color. In 24 b images, PNG supports transparency by designating an alpha channel to be transparent, i.e. the color will change to the background color. The later versions of Netscape Navigator and Microsoft Internet Explorer both support the PNG format.
point
See pt.
pointer
(1) Aka mouse pointer or cursor. A small arrow or symbol usually moved by a mouse or other pointing device.

(2) Aka indirect addressing. In programming, a pointer is a datatype whose value is a reference (a memory address) as opposed to some value (EG: "hello" or some number). Determining the value of that the pointer refers  to is called dereferencing. Dereferencing a pointer may yield some data, an object, or null.
Point of Presence
See POP.
Point-to-Point Protocol
See PPP.
Point- to- Point Tunneling Protocol
See PPTP.
Polish notation
A method of mathematical notation created by Jan Łukasiewicz in 1920. Operators are placed before operands. EG: + 1 2 instead of 1 + 2. Some programming languages such as LISP and Scheme make heavy use of Polish notation. See also RPN.
polymorphism
When members (i.e. properties, methods, or events) have similar names, interface, and usage for two or more classes. EG: If the method "move" is polymorphic, then its syntax and function would be similar for different classes/objects:   Form.Move and Picture.Move. Polymorphs have to be encapsulated, i.e. created with difficulty by the creator but utilized with ease by the user. Polymorphism can be inherited from a parent class. Alternatively, polymorphism can be achieved by giving objects interfaces to common components such as an ActiveX component.
POP
(1) Post Office Protocol. Aka POP3. Protocol used to download e-mail. When you set up your e-mail account. You need to know the name of the POP server (eg pop.isp.com) and POP user name which may or may not be the same as your network logon name.

(2) Point of Presence. Extension of network infrastructure. Usually a room, full of routers and modems, with a direct connection to other POPs on the network. It typically allows end users to connect to the Internet with modems. See also gigaPOP.
port
(1) A interface point on a computer where a device may be connected. There are various ports for hard disk drives, floppy disk drives, display screens, mice, printers, modems, and other peripherals. Some are located external to the machine but some are internal to the machine.

Common ports include:
  • ATA/IDE, disk drive implementation with controllers on the drive. Comes in many flavors.
    • ATA-2/FastATA/EIDE, supports disks with 4-17 Mb/s transfer and up to 8.4 G
    • ATA-33/UltraATA/Ultra-DMA, 33 Mb/s
    • ATA/66, 66 Mb/s
    • ATA/100, 100 Mb/s
  • SCSI port, a internal/external parallel port with high data tranfer rate. Comes in many flavors.
  • Firewire/IEEE 1394, an external 400 Mb/s bus
  • RS-232 (either DB-25 or DB-9), a serial port.
    • RS-422, backward compatible but faster and more immune to electrical interference. Macs have RS-422 ports.
  • PS/2 (mini DIN 6-pin), a serial port that was commonly used for mice.
  • Centronics port (DB-25), a parallel port commonly used for printers.
    • EPP or ECP, backward compatible but supports bi-directional and faster data transfer.
  • ADB (Apple Desktop Bus), a daisy-chainable serial port common for keyboards and mice on Macintosh.
  • USB (Universal Serial Bus), a 12 Mb/s daisy-chainable serial port for up to 127 devices, common since the iMac. It should eventually replace the other serial and parallel ports.
    • USB 1.1. 12 Mb/s.
    • USB 2. 480 Mb/s.
Four serial ports are commonly referred to as COM1, COM2, COM3, and COM4. The parallel ports are commonly printer ports referred to as LPT1 and LPT2, although LPT2 is usually disabled.

(2) To move a program from one type of computer to another. To port an application, you need to rewrite sections that are machine dependent, and then recompile the program on the new computer. Programs that can be ported easily are said to be portable.
port number
Aka TCP port, TCP port number, TCP port address, port number, port address, data port, and port. Any application or process that uses TCP for its transport is assigned a port number. These ports are often used with UDP as well. A port number is 16 bit (1-65535)

Around 250 ports are well known and are usually less than 1024. Here are some common port numbers.
PORT #	PROCESS NAME
--------------------
1       tcpmux (tcp port service multiplexer)
5       rje (remote job entry)
7       echo
13      daytime
18      msp (message send protocol)
20      ftp (data)
21      ftp (control)
22      ssh
23      telnet
25      smtp (simple mail transfer protocol)
29      msg icp
37      time
42      nameserv (host name server)
43      nicname (whois)
49      login (login host protocol)
53      dns (Domain Name System)
69      tftp (trivial file transfer protocol)
70      gopher
79      finger
80      http
103     x400
108     sna gateway access server
109     pop2
110     pop3
115     sftp (simple file transfer protocol)
118     sql services
119     nntp (newsgroup)
135     rpc
137     netbios (name service)
139     netbios (datagram service)
143     imap
150     netbios (session service)
156     sqlsrv (sql server)
161     snmp
179     bgp (border gateway protocol)
190     gacp (gateway access control protocol
194     irc (internet relay chat)
197     dls (directory location service) 
389     ldap (lightweight directory access protocol) 
396     novell netware over ip 
443     ssl (secures sockets layer) (esp. https)
444     snpp (simple network paging protocol) 
445     microsoft-ds smb
458     apple quicktime 
546     dhcp client 
547     dhcp server 
563     snews 
569     msn 
1080    socks
1433    microsoft sql server
3306    mysql
3309    remote desktop
3782    roger wilco
5632    PCAnywhere
5900    vnc
6112    blizzard

See also sockets.
Portable Document Format
See PDF.
Portable N etwork Graphics
See PNG.
portal devices
Devices on networks which act as the go-betweens of local and long distance network segments of media. The common portal devices are repeaters, hubs, bridges, routers, brouters, and gateways. See also my article on Portal Devices.
position image
A crude image not intended for final usage but is used to indicate the placement of an image in a document. Such a document is often marked FPO (For Position Only).
Post Office Protocol
See POP.
postfix notation
See RPN.
POSTs
Power-On Self Tests. A series of system checks performed at startup. It makes sure that the hardware is functioning and timed together.
PostScript
See PS.
PostScript Printer Description
See PPD.
POTS
Plain-Old Telephone Service. See PSTN.
PPCP
Power Personal Computer Platform. See CHRP.
PPD
PostScript Printer Description. A description of the destination output device utilized in creating PostScript files.
ppi
pixels per inch. Same as dpi. See also resolution.
PPP
Point-to-Point Protocol. Protocol for connecting computers via phone. It allows the user a variety of applications to access the server as opposed to shell or terminal access which usually can only be accessed by specific programs. Usually PPP is preferred over SLIP.
PPTP
Point- to-Point Tunneling Protocol. An improvement over PPP with encryption security. It is used in VPNs (Virtual Private Networks).
PRAM
Parameter Random Access Memory. Battery powered RAM that stores important system settings when the power is off. For Macs, this may returned to factory settings by holding down Command-Opt-P-R during startup. See also CMOS.
precedence
Rules that decide which operators act first when multiple operators are present. A common order is:
Symbol Explanation
( ) values between parenthesis
^ exponentiation
- negation
* / multiplication or division
\ % integer division, i.e. division discarding the modulus
mod modulus, i.e. the remainder after integer division
+ - addition or subtraction
& string concatenation
precision
In numbers or datatypes, precision refers to the number of significant digits. EG: 123, 1.23, and 0.123 all have three significant digits. Precision is often tagged with scale, where scale indicates the number of digits allowed in the fractional portion of a number.
Precision Graphics Markup Language
See PGML.
prefix notation
See Polish notation.
preemptive multitasking
See multitasking.
Pretty Good Privacy
See PGP.
PRI
Primary Rate Interface. aka 23B+D line. An ISDN line that has 23 bearer or B channels, each at DSO rates of 64kb/s, and a data or D channel.
Primary Domain Controller
See domain controller.
primary key
In databases, it is a column or combination of columns in a table that contains a unique value for each row.
Primary Rate Interface
See PRI.
Printer Access Protocol
See PAP.
printer font
See outline font.
Private Branch Exchange
See PBX.
procedure
A block of code that gets executed. Event procedures are executed when a specific event occurs like clicking a button. Function procedures are summoned by name (usually within other procedures) and  given arguments to process; the function procedure then returns a result associated with the function name. A sub procedure is like a function but does not necessarily return a result associated with the name and can return multiple results.
process
A request, demand, or task asked of a computer. An executing program. A multitasking computer can run or appear to run multiple processes at a time. See also thread and multithreading.
processing memory
Aka main memory. Volatile memory that loses its contents when the power is turned off. This is analogous to words, numbers, and symbols you manipulate live on scrap paper. Since processing memory utilizes RAM chips, the terms are often interchangeable.

If there is not enough processing memory, the computer may swap data in and out of processing memory or utilize virtual memory. See also storage memory.
processor
See CPU.
program
(1) As a noun, it is a set of statements or a collection of commands and instructions that detail a complete algorithm for a computer in a computer or programming language. See also software.

(2) As a verb, to write a program.
Program Design Language
See PDL.
programming language
A language system, with its own vocabulary, grammar, and syntax, that is used by humans to communicate with computers. See also my article on Programming Languages.
PROM
Programmable Read Only Memory. Standard ROM chips are programmed as part of their manufacturing process, in contrast PROM chips are made blank but can be encoded with a program so it can function as a ROM chip. See also PLD, EPROM, and EEPROM.
property
In OOP (Object Oriented Programming) the property of an object is an appendage to an object which thus  provides the name of a literal. EG: thing.husband = "fred". This is in contrast to a "method" which would provide the name of a function.
Protocol
Sets of rules and standards agreed upon to facilitate communication. Examples: HTTP, SMTP, PPP, POP, etc.
Provisioning
(1) In telecommunications, provisioning is providing or setting up telecommunications to a user or customer, including wiring, equipment, and signal transmissions.

(2) In information technology, provisioning covers not only telecommunications provisioning, but also granting authorization to systems, network applications, and data approrpriate to the user. This includes authentication, permissions, security, privacy, login, and passwords. Provisioning is involved with the setup —once the user is in, then the user's experience falls into the domain of system operations (SysOps).
proxy server
A go-between server. It usually does one or both of the following:

(1) It improves performance for a group of users by caching commonly accessed documents instead of referring the users to the actual server.

(2) It filters requests to and from a network for security/firewall reasons. By examining packets, it can block unauthorized access from outside of the network and it can also stop users from within the network from accessing unauthorized sites.

See also firewall.
PS
PostScript. A programming language developed by Adobe in 1985 which is used by many DTPs that encodes documents as commands and data. It supports vector objects, rasterized images, and text. It is independent of the application which created the file and is also generally output device independent as well. The language utilizes RPN.
 
PS was one of the first to utilize outline fonts. Adobe fiddled around with different types of fonts classified as Type 1, 2, and 3. Only Type 1, the highest quality is supported. For each PS font you need the equivalent screen font as well as the printer font. If you are using a PS printer it may have the particular font already loaded, if not, the font will have to be downloaded to the printer.
PS/2
See serial port.
pseudo-code
See PDL.
PSTN
Public Switched Telephone Network. Aka POTS (Plain-Old Telephone Service). The international telephone system based on analog voice data carried over copper wires. This is in contrast with newer telephone networks based on digital technologies such as ISDN and FDDI.

It may also be said that PSTN is one of two global networks. The other is the Internet. PSTN is predominantly voice/analog and the Internet is predominantly data/digital, but soon the two will merge and voice and data will be done digitally.

PSTN voice primarily travels over its core TDM. However, more and more voice is being carried over alternatives such as frame relay, ATM, and IP.
pt
Point. A unit of measurement common in page layout.
     1 in =     6 pc =   72 pt = 1440 twip
   1/6 in =     1 pc =   12 pt =  240 twip
  1/72 in =  1/12 pc =    1 pt =   20 twip
1/1440 in = 1/240 pc = 1/20 pt =    1 twip
PU
Physical Unit. An SNA term for an actual terminal, printer, computer, etc.
public key encryption
Aka Diffie-Hellman encryption. Aka asymmetric encryption. An encryption system developed in 1976 by Whitfield Diffie and Martin Hellman. The system utilizes two keys: a public encrypting key and a private/secret decrypting key, both of which are created at the same time. A sender sends a message to a receiver encrypted via the receiver's public key. The receiver then uses his or her private key to decrypt the message.

The public and private keys are uniquely related, but it is virtually impossible to deduce the private key if you know the public key. Senders will probably have to know different public keys for many different people. LDAP may be used to track people's public keys. PGP is a popular public key organization. See also symmetric key encryption, RSA, and digital certificate.
Public Switched Telephone Network
See PSTN.
Publish and Subscribe
Mac OS technology that shares an original document amongst several other documents, even if created by other programs. One program, designated the publisher, can pick an object from one of its documents to create another file, called edition, which can be subscribed to by another program's document. The link between publisher and edition can be automatic, manual, or broken off. The link between edition and subscriber can also be automatic, manual, or broken off. The Windows equivalent is OLE.
pubs
A sample database provided by Microsoft. See also Northwind.
pull
See push.
push
Push is the opposite of pull. Users use web browsers to pull information in but e-mail is pushed to users by someone else. Pull is good for low volumes of data, eg searching. Push is good for high volumes of data, downloading big applications.
PVC
Permanent Virtual Circuit. See virtual circuit.

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