PC Doctor On Call - Home - Computer Repairs & Upgrades, Northern Ireland

Packet - The data transfer unit used in network and modem communications. Each packet contains data and a header which contains information as to the sending machine and the receiving machine, as well as the necessary information for the receiving machine to reassemble the data at its end. See also Network and Modem.

Packet Switching Network - A public telephone system network which routes packets of information. See also Network and Packet.

Paging - A method in which an operating system low on free memory swaps idle data and programs to disc into a special file called a swap file. When the data or program is needed again, something else is swapped so allow the data or program back into memory. See also Operating System, Memory, Data, Programs, Disc and File.

Palmtop - A hand held computer (or computing device) perhaps incorporating mobile telephone technologies. Commonly used as electronic diaries or PIM's (personal information managers). They can be linked to desktop computers via a short cable for synchronising data (or databases) between the palmtop and desktop. See also PIM, Desktop, Data and Databases.

Parallel - All at the same time as opposed to serial which is one after another. The parallel port on your computer can send 8 bits in parallel at a time. See also Parallel Port and Serial Port.

Parallel Port - Also known as the LPT port. The 25pin D-type connector on the rear of a computer that printers and other devices can be connected to. See also LPT, Devices, Device Driver and Printer.

Parameter - An option passed to a program to change the way in which it behaves in a predefined way. The most common use of a parameter is in passing a reference to a file by using its filename, for example:- notepad my_file.txt, where my_file.txt is the parameter passed to the notepad program to indicate open the file called my_file.txt into memory ready for editing. See also Program, File, Filename and Memory.

Parity Bit - In modem transfers of 8bits, the parity bit is the ninth bit which is used to make sure the data has received correctly by the recipient machine. The number of parity bits can be zero, one or two to make the total number of bits received in a byte odd or even depending on the agreement between the transmitting and receiving ends. See also Modem, Bit and Byte.

Pascal - A OOP language that is compiles into a machine independent pseudo code or p-code for short. The target machine must interpret this p-code to run the program. Modern Pascal compilers like Turbo Pascal and Delphi are able to compile into native code to run on Intel Pentium processors. See also OOP, Compiler, Interpreter, Delphi, Pentium and Processor.

PC - See also Personal Computer.

PCI - Peripheral Control Interface. A half bus speed 32bit interface that has become popular inside modern computers that allow expansion cards to be fitted that have an edge connector that fits inside the motherboards PCI slots. PCI is the successor to ISA/EISA and Micro channel. See also Interface, Motherboard, AGP, ISA, EISA, VLB and Micro channel.

PCM - Pulse Code Modulation. A method of transmitting digital data using square waves. The data is represented by the change in state instead of the voltage level.

PCMCIA - Personal Computer Memory Card International Association. PCMCIA is an interface standard used extensively in Laptops. The Personal Computer Memory Card International Association (PCMCIA) is a non-profit trade association established in June of 1989 and headquartered in Sunnyvale, California. The organisation's charter is to establish, market and maintain a standard for PC Cards. See also PC, Memory, Interface and Laptop.

PCMCIA Card - The credit card sized device that fits into your laptop which can be a disk, modem, NIC (network interface card) or extra memory. See also Device, Laptop, Disc, Modem, NIC and Memory.

PDA - Personal Digital Assistant. A small hand held computing device especially designed to act like an assistant. Not suitable for general purpose computing as their operation is compromised by size, weight, battery life etc. A larger and heavier alternative would be a Laptop. See also Laptop.

PDC - Primary Domain Controller. A service that runs on an Windows NT Server that is responsible for the security of the system, the logging on of users and their permissions. There can only be one PDC in a Domain, but there may also be BDC's (Backup Domian Controller) in case the PDC computer fails. If this happens, a BDC can be promoted to the PDC to allow continued use of the computer system. A PDC will communicate with the BDC's on a frequent basis to ensure that user permissions, log in identities and passwords are replicated in case of failure. A BDC adds some resilience to a large Windows NT Domain. See also Windows NT, Server, Service, Logging On, BDC, Domain, Permissions and Password.

Peer-to-Peer Network - A computer network where all the computers have equal status and all resources can be shared between all parties. See also Network and Resources.

Pentium - A processor range launched by Intel as the successor to the 80486 or i486 for short. Speeds range from 50MHz to 233MHz. Later 200Mhz and 233Mhz had MMX included. The package type was a slat square case with pins underneath to fit a socket 7 motherboard. A heat sink with a fan must be fitted to keep it cool. See also Processor and MMX.

Pentium II - A processor range by Intel as the successor to the Pentium MMX. Speeds range from 233MHz to 450Mhz. The package type was a small daughterboard with an edge connector that fits into a slot on the motherboard. This slot is called "Slot 1" and is not to be confused with "Slot A". Pentium II's up to and including 333MHz use a 66MHz bus. A heat sink with a fan must be fitted to keep it cool. Pentium II's 350MHz and above use a 100MHz bus. A heat sink with a double fan must be fitted to keep it cool. See also Processor, Bus, Slot A and MMX.

Pentium III - A processor range by Intel as the successor to the Pentium II. Speed range from 450Mhz to 600MHz. The package type was a small daughterboard with an edge connector that fits into a slot on the motherboard. This slot is called "Slot 2" and is not to be confused with "Slot 1" or "Slot A". Pentium III's use a 100MHz bus. A heat sink with a double fan must be fitted to keep it cool. See also Processor, Bus, Slot 1 and Slot A.

Permissions - While your session with a computer is active, you will be assigned permissions to view, edit, update data and to run programs. Your permissions are granted to you by your system administrator or a person responsible for computer security.

Personal Computer - Also known as a desktop. A modern multi-purpose electronic computing device that can run multiple software applications concurrently for a single business or home user. Modern computers employ the extensive use of graphics to make the use of the computer easier. See also Computer, Desktop, GUI, Software and Windows.

PIM - Personal Information Manager. A software application that is usually run on a palmtop (hand held computing device) that acts like an electronic diary, scheduler, e-mail processor and note pad. See also Palmtop and Device.

Plotter - A flat tablet device that has a number of coloured drawing pens and a robotic arm. The device driver will issue the commands to pick up a coloured pen and draw on the tablet. This type of device is ideal for CAD (Computer Aided Design) work. See also Printer and Device Driver.

Plus! - An add on package for Windows 95 or Windows 98 that contains a whole host of graphical goodies and utilities to please the user. See also Windows95/98 and GUI.

PNP - Plug and Play. The concept relates to being able to plug new devices into your computer and the operating system recognises that they're attached as just uses them. Should a device not be recognised, the operating system will ask you to install the necessary device controlling program called a device driver. See also Operating System and Device Driver.

POP - Point of Presence. The email format that individual users will use to receive email over the Internet. The e-mail program uses POP as the communication language with the remote server, i.e. the Internet Service Providers Server. The current standard for POP is version 3 or sometimes referred to as POP3. A POP3 e-mail mailbox will have an address like:- my_mail77@my_ISP.com or mark@smith77.my_ISP.com. Corporates will use SMTP for e-mail transfer. See also Networks, e-mail SMTP and Internet.

Printer - A generic term used to describe how a computer provides printed text output onto paper. Types of printers are, Laser, Inkjet, Dot Matrix, Daisy Wheel etc. See also Laser Printer, Dot Matrix Printer and Ink Jet Printer.

Processor - Central Processing Unit, or just processor. The device that executes program code on a computer. There may be more than one CPU in a computer. See also Program.

Profile - A set of security configurations specific to one person or class of user. See also Security.

Protected Mode - An archaic way of reserving memory that could not be accessed by more than one program running on a DOS based computer. See also Memory, Program and DOS.

Protocol - A set of standards which govern the transmission of data over a network connection. See also Network.

PSU - Power Supply Unit. The 110/240 volt mains power supply must be changed to voltages suitable for use on the motherboard. The power supply unit does this job. It has a large fan in it to keep it cool. See also Motherboard.

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