Online Computer Terms Dictionary - P

process

1. <operating system, software> The sequence of states of an executing program. A process consists of the program code (which may be shared with other processes which are executing the same program), private data, and the state of the processor, particularly the values in its registers. It may have other associated resources such as a process identifier, open files, CPU time limits, shared memory, child processes, and signal handlers.

One process may, on some platforms, consist of many threads. A multitasking operating system can run multiple processes concurrently or in parallel, and allows a process to spawn "child" processes.

(2001-06-16)

2. <business> The sequence of activities, people, and systems involved in carrying out some business or achieving some desired result. E.g. software development process, project management process, configuration management process.

(2001-06-16)

Process and Experiment Automation Real-Time Language

<language> (PEARL) A real-time language for programming process control systems, widely used in Europe. Size and complexity exceeds Ada. Defined in DIN 66253 Teil 2.

["Programmiersprache PEARL", Beuth-Verlag, Nov 1980].

(2000-08-16)

Process Design Language 2

<language> (PDL2) A language developed for the Texas Instruments ASC computer.

["Texas Instruments Process Design Methodology - Design Specification: Process Design Language", Volume I (Sep 1976)].

[Mentioned in "An Overview of Ada" J.G.P. Barnes, Soft Prac & Exp 10:851-887 (1980)].

(1995-08-13)

process ID

process identifier

process identifier

<operating system> (PID) An integer used by the Unix kernel to uniquely identify a process. PIDs are returned by the fork system call and can be passed to wait() or kill() to perform actions on the given process.

(1996-12-09)

processing

<data processing, signal processing> Performing some predefined sequence of operations on an input to produce an output or change of internal state; activity specifically involving the computer's CPU.

The term is often qualified: "data processing" treats digital data, "signal processing" treats analog data (possibly in digital form), "word processing" takes in typed human language input and produces digital documents, image processing transforms digital images.

(2003-10-23)

processor

central processing unit

Processor Direct Slot

<hardware> (PDS) Apple Computer's name for a local bus connection. Most Macintoshes have only one PDS connector. Different Apple computers have different PDS specifications.

(1995-05-02)

processor farm

<computer, parallel> A parallel processor where tasks are distributed, or "farmed out", by one "farmer" processor to several "worker" processors, and results are sent back to the farmer. This arrangement is suitable for applications which can be partitioned into many separate, independent tasks, the canonical examples being ray tracing and the Mandelbrot set. In order to be efficient, the extra time spent on communications must be small compared to the time spent processing each task.

(2001-05-28)

processor time

<software> The amount of time a process takes to run, given that it has exclusive and uninterrupted use of the CPU. Note that in a modern computer, this would be very unusual, and so the processor time calculation for most processes involves adding up all the small amounts of time the CPU actually spends on the process.

Some systems break processor time down into user time and system time.

Compare wall clock time.

(1998-03-13)

process scheduling

multitasking

process table

<operating system, process> A table containing all of the information that must be saved when the CPU switches from running one process to another in a multitasking system.

The information in the process table allows the suspended process to be restarted at a later time as if it had never been stopped. Every process has an entry in the table. These entries are known as process control blocks and contain the following information:

process state - information needed so that the process can be loaded into memory and run, such as the program counter, the stack pointer, and the values of registers.

memory state - details of the memory allocation such as pointers to the various memory areas used by the program

resource state - information regarding the status of files being used by the process such as user ID.

Accounting and scheduling information.

An example of a UNIX process table is shown below.

 SLOT  ST  PID  PGRP  UID  PRI  CPU  EVENT  NAME  FLAGS
  0    s    0     0     0   95   0  runout  sched load sys
  1    s    1     0     0   66   1    u     init  load
  2    s    2     0     0   95   0  10bbdc  vhand load sys

ST shows whether the process is paused or sleeping (s), ready to run (r), or running on a CPU (o).

PID is the process ID.

PGRP is the process Group.

UID is the user ID.

PRI is the priority of the process from 127 (highest) to 0 (lowest).

EVENT is the event on which a process is paused or sleeping.

NAME is the name of the process.

FLAGS are the process flags.

A process that has died but still has an entry in the process table is called a zombie process.

(1998-04-24)