What is Command Interpreter

7/27/2019 What is Command Interpreter

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What is command interpreter?

In computing, a shell is a piece of software that provides an interface for users. Typically,

the term refers to an operating system shell which provides access to the services of a

kernel.

A command line interpreter (also command line shell, command language interpreter) is a

computer program that reads lines of text entered by a user and interprets them in the

context of a given operating system or programming language.

In computer science, an interpreter normally means a computer program that executes, i.e.

performs, instructions written in a programming language. While interpretation and

compilation are the two principal means by which programming languages are

implemented, these are not fully distinct categories, one of the reasons being that most

interpreting systems also perform some translation work, just like compilers. An interpreter

may be a program that either

1. executes the source code directly

2. translates source code into some efficient intermediate representation (code) and

immediately executes this

3. explicitly executes stored precompiled code[1] made by a compiler which is part of the

interpreter system.

A compiler is a computer program (or set of programs) that translates text written in a

computer language (the source language) into another computer language (the target

language). The original sequence is usually called the source code and the output called

object code. Commonly the output has a form suitable for processing by other programs

(e.g., a linker), but it may be a human-readable text file.

what is shell?

Shell

Most people know of shells as small protective coverings for certain

animals, such as clams, crabs, and mollusks. You may also find a shell

on the outside of an egg, which I highly recommend you remove

before eating. In the computer science world, however, a shell is a


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software program that interprets commands from the user so that

theoperating systemcan understand them and perform the

appropriate functions.

The shell is a command-line interface, which means it is soley text-based. The user can type commands to perform functions such as run

programs, open and browsedirectories, and view processes that are

currently running. Since the shell is only one layer above the operating

system, you can perform operations that are not always possible using

the graphical user interface (GUI). Some examples include moving files

within the system folder and deleting files that are typically locked.

The catch is, you need to know the correct syntax when typing the

commands and you may still be prompted for a password in order to

perform administrative functions.

Shells are most commonly associated withUnix, as many Unix users

like to interact with the operating system using the text-based

interface. Two common Unix shells are the Bourne shell and the C

Shell, which is used by BSD. Most Unix systems have both of these

shells available to the user. Windows users may be more familiar with

DOS, the shell that has long been included with the Windows operatingsystem. Most computer users have no need to use the shell interface,

but it can be a fun way to perform functions on your computer, as well

as impress your friends.

What is spooling?

Acronym forsimultaneous peripheraloperations on-l ine,spoolingrefers to puttingjobsin abuffer, aspecial area inmemoryor on adiskwhere adevicecanaccessthem when it is ready. Spooling isuseful because devices accessdataat different rates. The buffer provides a waiting station where

data can rest while the slower device catches up.The most common spoolingapplicationisprint spooling. In print spooling,documentsare loaded intoa buffer (usually an area on a disk), and then theprinterpulls them off the buffer at its own rate.Because the documents are in a buffer where they can be accessed by the printer, you can performother operations on thecomputerwhile the printing takes place in thebackground. Spooling also letsyou place a number of print jobs on aqueueinstead of waiting for each one to finish beforespecifying the next one.

What is meant by background process?
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n.)(1)Multitaskingcomputersare capable ofexecutingseveraltasks, orprograms, at the same time.In some multitaskingsystems, one of the processes is called theforegroundprocess , and theothers are calledbackground processes.The foreground process is the one that acceptsinputfrom thekeyboard,mouse, or otherinputdevice. Background processes cannot acceptinteractiveinput from auser, but theycanaccessdatastoredon adiskandwritedata to the video display. For example, someword

processorsprintfilesin the background, enabling you to continue editing while files are being printed.This is calledprintspooling. In addition, manycommunicationsprograms are designed torunin thebackground. Background processes generally have a lower priority than foreground processes sothat they do not interfere with interactiveapplications.Even thoughDOSis not a multitaskingoperating system, it can perform some specialized tasks,such as printing, in the background.Operating environments, such asMicrosoft WindowsandtheMacintoshoperating system, provide a more general multitaskingenvironment.(2) The area of adisplay screennot covered bycharactersandgraphics. The background is like acanvas on top of which characters and graphics are placed. Somemonitorsallow you to control thecolor or shading of the background.

What are daemons?

Pronounced DEE-mun orDAY-mun. Aprocessthat runs in thebackgroundand performs a specifiedoperation at predefined times or in response to certain events. The term daemon is aUNIXterm,though many otheroperating systemsprovide support for daemons, though they're sometimescalled other names.Windows, for example, refers to daemons as System Agents andservices.Typical daemon processes includeprint spoolers, e-mail handlers, and other programs that performadministrative tasks for the operating system. The term comes from Greek mythology, wheredaemons were guardian spirits.

Another answer?

The word "daemon" actually comes from the Greek language, meaning

an "inner or attendant spirit" (Oxford American Dictionary). This is afitting name, as a computer daemon is a constantly running program

that triggers actions when it receives certain input.

For example, a printer daemon spools information to a printer when a

user decides to print a document. A daemon running on a mail server

routes incoming mail to the appropriate mailboxes. Web servers use

an "HTTPD" daemon that sends data to users when they access Web

pages. While daemons were first used by theUnixoperating system,they have also been incorporated intoMac OS X, which is Unix-based.

Difference between the multitasking and multithreading?

Multi-Tasking - doing more than 1 thing at a time - Eating and talking at the same time

Multi-Threading - doing the same thing many times at once - reading a book at more than
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What is Command Interpreter