FILES

A file is a collection of related information

Files are kept in directories on a disk.

FILESThe two system areas on a disk

DirectoriesFile Allocation Table(FAT)

-They enable MS_DOS to recognize and organize the files on your disk.

-FAT is copied onto a new disk when you format it with the MS_DOS format command, and one empty directory is created, called the root directory.

File Allocation Table A table that the operating system uses to locate

files on a disk.

Due to fragmentation, a file may be divided into many sections that are scattered around the disk.

The FAT keeps track of all these pieces. In DOS systems, FATs are stored just after the boot sector.

File Allocation Table A file system to control how files & folders are stored on

your hard disk.

Files are stored in small clusters.

Smaller the cluster, more efficiently the disk stores information.

Cluster depends on the size of the partition, partition depends on the file system used.

File Allocation Table

Partitions larger than 2GB are not supported with FAT16.

Partitions smaller than 512MB are not supported with FAT32.

File Allocation TableAdvantages of FAT32 file system over FAT16:

Allows programs to open more quickly-36% faster. Uses smaller cluster size, hence more efficient use of

disk space-28% more disk space. Allows hard disk upto 2TB to be formatted as a

single drive-no need to partition the hard disk. Can relocate the root directory and use backup copies

of FAT-computer less vulnerable to crashes.

Files

For DOS to run an application file , it has to be one of three kinds:

.COM .EXE .BAT

COM - A file in machine language, must be less than 64K in size.

EXE - A file in machine language, can be larger than 64K. EXE files also have information

at the beginning of the file that tells DOS what type of file it is and how to load and run it.

BAT - A batch file that is written with a text editor and is in ASCII text format, it contains DOS commands

that are executed in batch mode, which means that each command is executed in sequence until the file ends.

DIRECTORIES

Directories are a way of dividing your files into convenient groups of files.

Directories also contain information on the size of files, and the dates they were created and updated.

DIRECTORIES

Directories can also contain subdirectories.

A multilevel directory structure can be thought of as a tree structure, with the root at the top.

MULTILEVEL DIRECTORY STRUCTURE

ROOT

DIR DIR DIR

DIR DIR DIRFILE FILE

FILE FILE FILE FILE FILE

C:\>

PATHS

When you use multilevel directories, you must tell MS-DOS where the files are located in the directory structure.

This can be done by giving

MS-DOS a pathname to the file.

PATHNAME

a pathname is a sequence of directory names followed by a filename, each separated from the previous one by a backslash.

dir_name\dir_name\file_name

USING DIRECTORIES

A:\USER\JOE . <Dir> 12-02-03 10:09a

.. <Dir> 12-02-03 10:09a

. working directory \USER\JOE .. Parent directory \USER

COMMANDS

A command is a way of communicating with the computer.

COMMAND OPTIONS

Used to give MS-DOS commands extra information.

The format of all MS-DOS commands: command [options….]

COMMAND OPTIONS Where options can be one of the following:

drive filenamepathname switches - options which control MS-DOS commands.arguments- provide more information to MS-DOS

commands. Eg. ON or OFF

INTERNAL COMMANDS

The way you do anything in DOS is through commands that the computer understands.

A command may cause the computer to take some action, or to execute some file.

INTERNAL COMMANDS

COMMAND.COM

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.

INTERNAL COMMANDS If you have created a DOS boot disk, it will contain three

files,

IO.SYS

MSDOS.SYS

COMMAND.COM.

HIDDEN

INTERNAL COMMANDS

The third file, COMMAND.COM, must be in the root directory.

Since it is on the boot disk (you cannot boot without it), that means that the commands it contains are available to you when you boot from this disk.

INTERNAL COMMANDS

The internal commands contained within COMMAND.COM are the commands that are used in writing batch files.

The batch file will not run properly if it cannot find COMMAND.COM.

DOS Operating System

The interface is

Command Line Interfaceor

Character User Interface

No mouse,no menus, no graphical components.

DOS Operating System

Text commands were entered from the keyboard, and the computer's response appeared as text on the monitor.

DOS Operating System

DOS controlled some aspects of the computer hardware, particularly disk access and basic CPU operations, but it was still common to need to configure the video display, sound card, printer, etc. for each application that would use them.

DOS Operating System

DOS

a single-tasking operating system,

i.e only one program could be run at a time.

INTERNAL COMMANDS Some Internal Commands contained within the

COMMAND.COM command interpreter: break cd chdir cls copy date del dir echo erase exit md mkdir move path pause prompt rd rem ren rename rmdir type ver vol

EXTERNAL COMMANDS

Not all DOS commands are understood by COMMAND.COM.

There are commands called external commands that reside as separate files on your hard drive, and must be called specifically for you to use them.

EXTERNAL COMMANDS

If you look in your DOS directory on your hard drive (usually C:\DOS), you will see these external commands represented by files that are either *.EXE or *.COM files.

EXTERNAL COMMANDS Some External Commandsappend assign attrib chkdsk Comp deltree diskcomp diskcopy Doskey edit fc fdisk find format graphics help label more msbackup msav print replace restore scandisk Sort sys tree undelete unformat xcopy

THE PATH

The Command Line Everything you do in DOS is done from the command

line. The command line begins with a prompt, which is the computer's way of saying

"I'm ready. Give me something to do."

The prompt usually looks something like this:

C:\>

THE PATH If DOS does not find this file, it will consult

something called the PATH. This is a list of directories that DOS has been instructed to check whenever it cannot find a file in the current active directory

THE PATH

You can see what the path is for your computer at any time by using the PATH command. Just type "path" at the DOS prompt, and you will get back your path. Here is what I got on one of my machines:

C:\>path

THE PATH that is set in the AUTOEXEC.BAT. This is a batch

file that automatically executes (hence the name) when you boot your computer.

You can edit this file with the DOS program EDIT. To see or edit the contents of this file you need to enter the following command: C:\>edit autoexec.bat