Data Dictionary - P


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  • Packet
  • Packing Density
  • Pad Character
  • Padding
  • Page Fault
  • Parallel Access
  • Parallel Computer
  • Parallel Transmission
  • Parent/Child
  • Parity Check

In general usage, a unit of information transmitted as a whole from one device to another on a network. In packet-switching networks, a packet is defined more specifically as a transmission unit of fixed maximum size that consists of binary digits representing both data and a header containing an identification number, source and destination addresses, and, sometimes, error control data.

Packing Density
The number of storage units per length or area of a storage device. Bits per inch is one measure of packing density.

Pad Character
In data input and storage, an extra character inserted as “filler” to use up surplus space in a predefined block of a specified length, such as a fixed-length field.

In data storage, the addition of one or more bits (usually zeros) to a block of data in order to fill it, to force the actual data bits into a certain position, or to prevent the data from duplicating a bit pattern that has an established meaning, such as an embedded command.

Page Fault
The interrupt that occurs when software attempts to read from or write to a virtual memory location that is marked “not present.” The mapping hardware of a virtual memory system maintains status information about every page in the virtual address space. A page either is mapped onto a physical address or is not present in physical memory. When a read or write to an unmapped virtual address is detected, the memory management hardware generates the page fault interrupt. The operating system must respond to the page fault by swapping in the data for the page and updating the status information in the memory management unit.

Parallel Access
Also called simultaneous access. The ability to store or retrieve all of the bits composing a single unit of information, such as byte or a word (usually two bytes), at the same time.

Parallel Computer
A computer that uses several processors connected in parallel (Working concurrently). Software written for parallel computers can increase the amount of work done in a specific amount of time by dividing a computing task among several simultaneously functioning processors.

Parallel Transmission
The simultaneous transmission of a group of bits over separate wires. With microcomputers, parallel transmission refers to the transmission of 1 byte (8bits). The standard connection for parallel transmission – for example, from a computer to a printer – is known as the Centronics interface.

A term describing a relationship between processes in a multitasking environment in which the parents process called the child process and most often suspends its own operation until the child process aborts or is completed. Also, a relationship between nodes in a tree data structure in which the parent is one step closer to the root (that is, is one level higher) than the child.

Parity Check
The use of parity to check the accuracy of transmitted data.

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