Glossary P - X

P-X

PAGEFILE

A special file on disk used by the virtual memory management subsystem. It is used to store memory contents when memory space is needed for other purposes. Its contents are used to recreate the contents of memory pages when they are needed again.

PAGE TABLE

A database in memory containing virtual-to-physical memory mapping information. Used by the computer hardware to resolve process-generated memory addresses into their actual locations in physical memory. The contents of a page table change over time to reflect paging, swapping, and virtual memory creation and deletion. Its contents are kept current by the operating system.

PDF (ADOBE®Portable Document Format)

A file format capable of storing text and graphics images as if they were arranged on a newspaper or magazine page.

PERL

A scripting or "shell" language common on UNIX systems and other operating systems. It is the UNIX system's counterpart to the OpenVMS DCL (Digital command language) scripting capability. PERL is available for OpenVMS.

PRIMARY CPU

A CPU capable of carrying out any operating system function or one that controls the actions of other CPUs. For example, a certain hardware architecture or operating system may allow any CPU to carry out general instructions, but restrict I/O operations to the primary CPU. The primary CPU also begins the bootstrap process and causes any other CPUs to be started at the appropriate time.

PROCESSOR

A component in a computer system that carries out programmed instructions. Computer systems have numerous special-purpose processors in addition to one or more central processing units. When the term processor is used alone, the term usually refers to a central processing unit.

See also CPU (Central Processing Unit).

RETRIEVAL POINTER

A piece of data in a file header indicating the size and location of a file, or a portion thereof.

RMS (OpenVMS Record Management Services)

A part of OpenVMS that provides record-oriented I/O functions to programs.

SRM

The Console Subsystem used with OpenVMS.

See also CONSOLE SUBSYSTEM.

TELNET

A TCP/IP utility program providing remote login capability among computers on a network.

THREAD

A separate schedulable path of execution within a process. All threads in a process share the same process context, but may execute simultaneously on different CPUs.

X WINDOW SYSTEM

A suite of graphics software forming the basis for the DECwindows and Common Desktop Environment (CDE) graphical user interfaces.

XQP (extended $QIO processor)

A portion of the OpenVMS file system providing services that cannot be performed by the disk driver, including accessing a file on an I/O channel and providing virtual-to-logical block mapping.