Glossary: P

This page contains glossary terms beginning with the letter P.
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Word or Term Description or Explanation
Packet switching the technique in which a stream of data is broken into standardised units called 'packets', each of which contains address, sequence, control, size and error-checking information in addition to the user data
Palette this is a set of colours used for the desktop display - if the display has, say, 256 colours, the palette determines which actual physical colour is displayed on the screen for each of the colour numbers from 0 to 255
Pane a dialogue box that is attached to a particular window, e.g. the toolbox at the side of a Draw window
Parallel a device or communication channel is said to be parallel if the data is sent several bits at a time down several parallel wires - the printer port sends eight bits of data at a time
Parallel processor in some computers, such as the RiscPC, it is possible to have two processors working side-by-side, sharing the use of memory, data storage and peripherals - such processors are referred to as 'parallel processors'
Parent directory the directory within which the directory you are currently dealing with is stored (it is the opposite of a subdirectory)
Parity a method of checking for errors in transmitted or stored data - an extra bit (the parity bit) is added to each ASCII character so that the number of '1' bits is always odd (or always even)
Pascal originally developed in the late sixties as a programming language - it is the only main third generation language to be named after a person rather than a mnemonic - it was developed so that the developer had a language to teach his computing undergraduates which was simple and relatively easy to learn - it has been refined over the years to remove some deficiencies, one of which was it was the only 3rd generation language which originally had no string data type
Password when accessing a remote site, especially where certain services are only accessible to registered individuals, the system my require you to type in a code word or words to prove that you are who you say you are, and that password is necessary in order to grant you access
Patch extra code added in to the operating system to replace other code that has been found to be buggy or simply in need of improvement
Pathname this is the full name of a file or directory including the filing system, disc name (or number) and the sequence of directories that have to be opened to access that particular file or directory e.g. SCSI::Paul105.$.Archive.Bits.!Glossary
PBM (files) Portable Bit-Maps - a standard format for storing and transferring bit-mapped graphics
PC Card a PC processor on a separate card that can be used as a second processor in a RiscPC
PC Emulator a software application that can work within RISC OS or as a separate program taking over the whole of the computer's processing power which enables the computer to pretend to be an IBM PC and run (most of) the programs that are written to run under MS-DOS or DR-DOS on those computers
PC Expansion Card an expansion card containing a PC processor plus memory plus some I/O capability that can allow PC programs to be run within the RISC OS environment
PCB Printed Circuit Board - a piece of insulating material covered with conducting tracks, used to interconnect electronic components to make up an electronic circuit
PCI a computer bus: width 32 or 64 bits; clock 33 MHz; maximum transfer rate 133 Mbyte/s to 267 Mbyte/s - independent of processor type
PCMCIA Personal Computer Memory Card International Association - a committee which has set out the standard format for credit card-sized plug-in modules for personal computers, particularly portables - modules include memory cards, modems, sound cards, etc.
PD Public Domain - software that is released unconditionally, so that anyone can copy it, alter it, or use it as they wish - the author retains none of the exclusive rights associated with copyright - PD is often used incorrectly to refer to freeware or shareware
PDA Personal Digital Assistant - a handheld unit which in non-PC oriented, e.g. Psion
PDF (1) Portable Document Format - the native file format for Adobe Systems' Acrobat - PDF is the file format for representing documents in a manner that is independent of the original application software, hardware, and operating system used to create those documents - a PDF file can describe documents containing any combination of text, graphics and images in a device-independent and resolution-independent format - these documents can be one page or thousands of pages, very simple or extremely complex with a rich use of fonts, graphics, colour and images
PDF (2) Printer Definition File - a file within the RISC OS system that defines how pages are printed on a particular printer - carrying details of things like page size, margin width, special codes needed, etc.
PDF reader a program which enables PDF (Portable Document Format) files to be displayed on screen (but not created) and (possibly) to be printed out
PEM Privacy Enhanced Mail - Internet email which provides confidentiality, authentication and message integrity using various encryption methods
Pentium this is a 32-bit cpu with a 64-bit data bus produced by Intel Corporation
Peripheral an item of hardware such as a monitor or printer that can be connected to your computer
PGP Pretty Good Privacy - secure encryption using a public key system
Pinboard this is an application that makes use of the blank areas of the desktop - you can 'stick' various files or applications onto it so that they are easily accessible without having the filer windows open for each of the directories in which they are stored
Ping Packet Internet Groper - about the simplest Internet program - it simply sends an "Are you there?" type message and reports back how long it took - can be useful to see if you can make contact with another machine, e.g. ping gate.demon.co.uk
Pixel a tiny point of light and colour which is the smallest picture element in a video or computer image - the more pixels making up the image, the better the resolution
plan file see .plan file
Pling (!) under RISC OS, if a directory name starts with a pling, it is taken to be an application
Plonk used to represent the sound made by someone behaving stupidly or offensively in a newsgroup as he falls into a user's kill file, often written "*plonk*" and used as a form of public ridicule
PNG Portable Network Graphics - a format for storing and displaying images, designed to improve upon the GIF format
Pocket Book see Psion 3
Podule see Expansion card
PoP Point of Presence - a local phone number for access to Pipex, Demon or other Internet providers
POP/POP3 Post Office Protocol - POP is a networking protocol which allows users to download mail messages from a central mail server or "Post Office" - it is used in situations where the machine belonging to a user is not always available (e.g. a machine which is switched off when not in use, or one which only connects to the Internet occasionally via a dial-up link) - internet mail for the user is delivered to the Post Office machine and held there, awaiting collection by POP - there are several versions of the protocol, the most recent (and widely used) being version 3 which is described in Internet RFC 1725 and commonly referred to as "POP3" - "POP", without any qualifying version number, normally refers to version 2 which is described in Internet RFC 937
comparing POP3 with SMTP, the other main e-mail transfer protocols, the major difference is the decision as to which party is in the driver's seat - with SMTP, the server is in charge of delivery, the client has to wait passively for the server to send the messages to it - with POP3, the client is in charge - it interrogates the server to determine what messages are available, and then requests them individually
POP requires a password and is therefore secure, while SMTP does not require a password and therefore can be used by anyone - this causes problems when spammers use a node other than their own to send mail - therefore preventing their own ISP from knowing that they sent the spam, and preventing recipients from knowing where the mail came from - because of this, there are moves afoot to make both sending and receiving mail using POP rather than a mixture as it allows the mail to be verified - it is coming from someone who is allowed to use that account - potentially reducing spam
Pop-up menu a menu available by clicking an icon within a dialogue box - the icon is often placed alongside a display showing the current setting of that option
Portal a website that aims to be a "doorway" to the World-Wide Web, typically offering a search engine and/or links to useful pages, and possibly news or other services - these services are usually provided for free in the hope that users will make the site their default home page or at least visit it often - most portals exist to generate advertising income for their owners
Post(ing) to put an article/message onto a newsgroup
Postmaster the person who deals with mail and answers mail-related questions on an Internet site - on a BBS, the postmaster is usually the sysop
PostScript a page description language used in some laser printers and imagesetters - PostScript is a defined standard so that applications using it can produce output that can be printed on any PostScript device
PPP (a.k.a. P3) - Point to Point Protocol - a standard for transmitting Internet Protocol (IP) data packets over phone lines - this is a newer and more robust protocol than SLIP - N.B. this is NOT for transfer of mail - it just transfers data, which could, of course, contain mail, but the protocol knows nothing about this
Printer driver this is the program that converts a document or file created by an application into information that your particular printer needs to reproduce the information on paper - the term can be extended to "printing" a file or document via a fax modem - the output is in the form which a fax modem can then transmit, the printed output appearing on the fax at the other end of the phone line
Printer manager an application that oversees the printing process
Printer server a device or piece of software on a computer to provide a 'network connection' for a printer - typically the printer would have a parallel port or USB connection and the printer server would allow anyone on the network to print to the printer - you can also buy printers with a network connection and printer server built in
PRM Programmers Reference Manual - a set of manuals covering many highly technical programming details of the RISC OS operating system
Processor see CPU
Program a set of instructions which tells a computer how to carry out a particular task
Prolog a high level computer language often associated with artificial intelligence programming
Prompt when the host system asks you to do something and waits for you to respond - for example, if you see "login:" it means type your user name
Protocol an agreed set of procedures which allows for the orderly transfer of data between two hosts via a communications network - it is essentially a common language which enables hosts to interwork. Examples are TCP, IP, FTP, HTTP, etc.
Protocol stack a set of protocols which, together, form a hierarchy - the protocols at the top of the stack use the protocols lower down to do their work - for example, consider a mail server on host A, delivering a message to a mail server on host B - the two servers communicate using the SMTP application protocol, but do this via a TCP connection - the TCP connection is achieved by firing IP packets into the network - the IP packets are sent over a serial link using SLIP - the individual binary digits of the SLIP packet are encoded as a series of electrical impulses on a copper twisted pair - inside host B, the reverse process occurs to reconstitute the IP packet, which is sent up through the TCP layer to the application protocol
Proxy server a web server that fetches pages at your request and stores them in its own memory - this is usually used in conjunction with a cache so that if you fetch the same page again, it will come from the cache rather than having to be refetched - if you have a number of users who are all looking at a similar set of documents (e.g. a class of students looking at the same site) a proxy server on your local net can speed up access because a given page only needs to be fetched from the 'outside world' once and from then on it is returned from the cache
PS/2 port the type of port allowing connection of mouse and keyboard to the computer
Psion 3 a palmtop computer which was highly successful and incorporated a large number of features of a desktop computer in something which would fit in a pocket, and included a word processor, spreadsheet, database, clock, and various other things - the Psion 3 was cloned by Acorn to give the Acorn Pocketbook - it was superseded by the Series 3a which Acorn cloned into the Pocket Book II - that has since been superseded by the Psion 3c and the Psion 5 (there was no Psion 4, as 4 is considered the number of death in Japan where Psions sell quite well)
Public Key
Cryptography
a method of encryption whereby a public key is made available by someone to those people who want to send messages to that person - the public key is used to encrypt the data, but only the private key held by the owner can decrypt the data

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