Friday, October 12, 2007

What do you do in your garage?

I wish I knew about this one before I finished setting up my garage that stores my motor bike and dad’s car. There is nothing much besides minor servicing and cleaning jobs that I undertake in my garage, but a visit to www.carguygarage.com makes me wish I did a few things else there too with some of their stuff set up, kind of showing it off to my friends at a garage party or sort. www.carguygarages.com carry over 1000 products for garages like fluorescent lighting, flooring, storage cabinets, etc.

A place you must visit, if you have anything on mind synchronous with “garages.”


(This is a sponsored post.)

External Commands

Continued in Everything about DOS...



In the previous post, we saw that INTERNAL COMMANDS are those commands that are in present in the file COMMAND.COM. These are loaded into the memory every time the computer boots up.

Obviously not all of the commands can be loaded into the system memory at boot-up because they may not be needed, may be they are used infrequently or maybe they are too heavy in size. These commands are, hence, not included in command.com but are placed separately as individual files in the Windows System Directory (x:\windows\system32\ for Windows XP but may depend on the installation if customized. X:\ is the drive letter in which the Windows is installed.)

These commands can then be called from command-line as and when needed. These commands are known as EXTERNAL COMMANDS

LIST OF EXTERNAL COMMANDS:

append

assign

attrib

backup

chkdsk

command

comp

dblspace

debug

defrag

deloldos

deltree

diskcomp

diskcopy

doskey

dosshell

edit

emm386

exe2bin

expand

fasthelp

fastopen

fc

fdisk

find

format

graftabl

graphics

help

himem

interlnk

intersvr

join

keyb

label

mem

memmaker

mirror

mode

more

msav

msbackup

mscdex

msd

nlsfunc

power

print

replace

restore

scandisk

select

setver

share

sort

subst

sys

tree

undelete

unformat

vsafe

xcopy

Please note that you might not find all of these files on every computer. This will depend on things like which version of DOS you have installed. In some cases Microsoft replaced one file with a different file in later versions. An example of this is CHKDSK (i.e. "Check Disk"). This name survives in Windows NT, but in DOS (and later, Windows) this program/applet was replaced by the later SCANDISK. So look at this as a list of some of the files you might find on your computer. You may have some that are not on this list, as well. Also, note that other programs will sometimes install files in the DOS directory. In particular, Windows 3.x installed many of its files in this directory, and sometimes updated the versions that DOS originally installed.

One file that is very important, though it is not a DOS command, is the included copy of BASIC. In earlier versions of DOS this was called GWBASIC, and in later versions, QBASIC. One of the important external commands, EDIT, is actually a BASIC program, and will not run unless BASIC is present.

Extensions, Help, and associated files

External commands are files, and as such have file extensions. Generally these will be either *.EXE or *.COM. An *.EXE file is what is called an executable file. This is a file that is compiled to run as a program. To this day, any Windows program is run from an *.EXE file. The other type. *.COM, is the original "Dot Com". This refers to a command file. A few of these files will be *.SYS, which are system files, such as the IO.SYS and MSDOS.SYS files we discussed in Lesson 2. Another file type is the *.OVL file, which means overlay. This file type is found with backup programs, particularly.

Often these external files will come with Help files as well. Help files have the extension *.HLP which can be viewed with Windows Help Viewer in-built program.


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Internal Commands

Continued in Everything about DOS...

COMMAND.COM is the filename of the default operating system shell (or command line interpreter) for DOS and 16/32bits versions of Windows (95/98/98 SE/Me). This file is loaded during the boot process, which means that COMMAND.COM is resident in memory at all times, and the commands that it understands are available to the user at all times It also has an additional role, as the first program run after boot, hence being responsible for setting up the system by running the AUTOEXEC.BAT configuration file, and being the ancestor of all processes.

As a shell, COMMAND.COM has two distinct modes of work. First is the interactive mode, in which the user types commands which are then executed immediately. The second is the batch mode, which executes a predefined sequence of commands stored as a text file with the extension .BAT. Its function as the default command interpreter is analogous to that of the Unix shells, although COMMAND.COM's functionality is considerably more limited than that of its Unix counterparts.

cmd.exe is COMMAND.COM's successor on Windows NT/2000/XP/2003 and OS/2. COMMAND.COM is also available on those systems to provide compatibility when running DOS applications. On NT systems, COMMAND.COM is run within the Virtual DOS Machine.


A command that is stored in the system memory and loaded from this file COMMAND.COM is known as INTERNAL COMMAND.

As I told in my earlier post in the series, all commands are run only after the Enter key is pressed at the end of the line. COMMAND.COM is not case-sensitive, meaning commands can be typed in either case and are all equivalent (so dir, DIR and DiR will all work in the same way).

List of Internal Commands

Here are all of the 62 Internal Commands contained within the COMMAND.COM command interpreter:

break

buffers

call

cd

chcp

chdir

choice

cls

copy

country

ctty

date

del

device

devicehigh

dir

dos

drivparm

echo

erase

errorlevel

exist

exit

fcbs

files

for

goto

if

include

install

lastdrive

lh

loadfix

loadhigh

md

menucolor

menudefault

menuitem

mkdir

move

not

numlock

path

pause

prompt

rd

rem

ren

rename

rmdir

set

shell

shift

stacks

submenu

switches

time

truename

type

ver

verify

vol



Some of these internal commands (e.g. dir, cd) are meant to be executed from the command line, or within a batch file, which is what we think of as a command. Others (e.g. files, switches) are generally used within a configuration file like CONFIG.SYS to help configure your system. Because both CONFIG.SYS and AUTOEXEC.BAT use commands that are found in COMMAND.COM, they must load later in the boot process.


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