Data Dictionary - P (continued)

P

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  • Partition
  • Pathname
  • PCMCIA
  • Peek
  • Peer
  • Peta
  • Petabyte
  • Physical Memory
  • Pico
  • Poke
  • Port

Partition
A logically distinct portion of memory or a storage device that functions as though it were a physically separate unit. The MS-DOS operating system, for example, can divide a hard disk into a primary partition and an extended DOS partition, each of which behaves as if it were physically distinct from the other.

In database programming, a subset of a database table or file. In a horizontal partition, data is separated by rows or records; in a relational database management system, horizontal partitions can usually be created based on primary key values. In a vertical partition, data is separated by columns or fields. Vertical partitioning (or projection of columns) often occurs during normalization of database design. Database files may be horizontally or vertically partitioned across multiple nodes in a distributed database.

Pathname
In a hierarchical filing system, a listing of the directories or folders that lead from the current directory to a file. For example, the MS-DOS pathname \book\chapter\myfile.doc indicates that the file myfile.doc is located in a directory called chapter, which is located in a directory called book beneath the root directory on the current drive.

PCMCIA
Abbreviation for Personal Computer Memory Card International Association, a group of manufacturers and vendors formed to promote a common standard for PC Card-based peripherals and the slot designed to hold them, primarily on laptop, palmtop, and other portable computers, as well as for intelligent electronic devices. PCMCIA is also the name of the standard for PC Cards, first introduced in 1990 as release 1.

Peek
To read a byte from an absolute memory location. POKE (store a byte in memory) and PEEK commands are often found in programming languages, such as BASIC, that do not normally allow access to specific memory locations. Peek can also refer to the act of looking at the next character in a buffer associated with a keyboard or other sequential input device without actually removing the character from the buffer.

Peer
Any of the devices on a layered communications network that operate on the same protocol level.

Peta
Abbreviated P. A prefix meaning 1 quadrillion (base 10 to the power of 15). In computing, which is based on the binary (base-2) numbering system, peta- has a literal value of 1,125,899,906,842,624, which is the power of two (base 2 to the power 50) closest to 1 quadrillion.

Petabyte
Abbreviated PB. Either 1 quadrillion bytes or 1,125,899,906,842,624 bytes.

Physical Memory
Memory actually present in the system, as opposed to virtual memory. A computer might have only 4 megabytes (MB) of RAM but support a virtual memory of 20 MB.

Pico
Abbreviated p; a prefix meaning one trillionth (base 10 to the power of negative 12). In the British numbering system, one million millionth.

Poke
To store byte into an absolute memory location. PEEK (Read a byte from memory) and POKE commands are often found in programming languages, such as BASIC, that do not normally allow access to specific memory locations.

Port
In computer hardware, a location for passing data in and out of a computing device. Microprocessors have ports for sending and receiving data bits; these ports are usually dedicated locations in memory. Full computer systems have ports for connecting peripheral devices such as printers and modems.

In programming, to change a program in order to run it on a different computer; more loosely, to move documents, graphics, and other files from one computer to another.

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