Disk Operating System

Transcription

1 Disk Operating System DOS stands for Disk Operating System. DOS controls the computer s hardware and provides an environment for programs to run. This system program must always be present when working with your computer. It manages the files and data throughout the system. It serves as the interface between you, your program and the rest of the computer. DOS (Disk Operating System) was the first widely installed operating system for personal computers. The first personal computer version of DOS, called PC-DOS, was developed for IBM by Bill Gates and his new Microsoft Corporation. He retained the rights to market a Microsoft version, called MS-DOS. DOS was (and still is) a non-graphical line-oriented command- or menu-driven operating system. User interface of DOS is simple but not "friendly". Why You Need DOS: There are a variety of reasons why you need DOS DOS controls the flow of information between you and the computer. DOS allows you to store information on your computer. DOS allows you to retrieve information stored on your computer. DOS interprets and translates the software you have on your computer. DOS gives you access to all its function (i.e. saving, copying, and printing files). Its prompt to enter a command at command prompt like this C:\> Parts of DOS: DOS consists of: an input/output system, a command processor and Several utilities. Input/output System: The input/output system consists of two files and a ROM (Read Only Memory) chip. The two files are on your disks and are loaded into memory when the computer starts. They are normally hidden from users view and not available for changing. Command Processor: The command processor is a file you see on the disk. Once read into the computer's memory, it usually resides there. There are times when the command processor will be overwritten in memory by a program and have to be reloaded when the program stops executing. The command processor (COMMAND.COM on your disk) performs three tasks: It handles critical interrupts: COMMAND.COM takes care of all demands for attention by parts of the computer. The user typing the Control-Break program break command is an example of an interrupt It handles critical errors: COMMAND.COM takes care of problems. For example, if you leave the disk drive door open during a disk operation COMMAND.COM is responsible for the error message you will see. It performs end-of-program housekeeping:

2 COMMAND.COM takes care of making the computer's memory available for other programs and reloading parts of itself if the program wrote over them. COMMAND.COM also places the C:\> prompt on the screen and interprets any command(s) you might type. In short, the command processor tells the rest of DOS what to do. Utilities: The utilities are individual program files found on DOS disk. While part of DOS, these files are not needed often enough to make it necessary or practical to keep them in the computer's RAM all the time. FORMAT.COM, the program that formats blank disks, is an example of a DOS utility. Sometimes these utilities are called external commands (as opposed to internal commands which are included as part of the file COMMAND.COM and remain resident in memory at all times; e.g., DIR and COPY). Primitives of the DOS systems have two parts: BIOS (Basic Input/output System): These are the fundamental routines that control the keyboard, video display and other peripherals. The BIOS is comprised of a ROM on the computer's main circuit board and the file IO.SYS, one of the two hidden files on your disk. Operating System: This is the main file-handling system for the computer. Actually, two systems exist: one for disk-based files and one for non-disk peripheral devices. They are in hidden file MSDOS.SYS. MS-DOS uses IO.SYS and MSDOS.SYS. Starting a Computer: The process of starting a computer is called booting up. When you start a computer it literally picks itself up by its bootstraps. When the power is turn on the computer first checks its memory and some other components (the POST, or Power on Self-Test). After this, the left (or top) disk drive will begin to spin and the boot process will commence. ROM BIOS loads Track 0, Sector 0 of the disk. This sector contains a short program that can read the rest of the input/output system. (Note: every disk, bootable or not, contains a boot sector program. Default Drive: The default drive is the first disk drive on which DOS will look for a program if no drive specification is given with the filename. The default drive letter is part of the prompt (unless someone has changed the prompt to eliminate it). A:\> indicates that drive A (the left or top drive in a two-drive system) is the default drive. DOS supports many more than drives A through C. You change drives by typing the desired default drive followed by a colon at the prompt. Rules for Filenames: Like devices, disk files have to be identified so DOS can address them. These filenames have specific rules. The basic form of a filename is: Filename.txt

3 The first part of the name to the left of the period is called the root name. The root name can be from one to eight characters long and cannot be the same as a device name. The second part to the right of the period is the extension. It is optional and, if used, can be one to three characters long. The period is used between the root name and extension and must be present if there is an extension. The following are legal and illegal characters in a filename: Legal: A-Z 0-9 $#&@!()-{}'`_~ Illegal: <>\^+=?/[]";,* plus control characters and the space What makes up a DOS Command? DOS commands are issued at the prompt C:\>. Whatever you type after that prompt that is not in the COMMAND.COM standard library is assumed to be the name of a file on the default disk and DOS will search for it under one of three names (in the order listed). If you type C\:> FILENAME DOS will look for: FILENAME.COM or FILENAME.EXE or FILENAME.BAT The first is a command file (note the COM extension). The second is an execution file (EXE extension). And, the third is a batch file (a series of DOS commands in a text file). The first file found will be read into memory and the command processor will start the program running. DOS Commands: There are two types of DOS commands: 1. Internal Commands. 2. External commands. Internal Commands: MD Command: Purpose: To make/create directory. Syntax: MD (drive:) (path) Directory Name. CD Command: Purpose: To change Directory. Syntax: CD (drive:) (path) Directory Name. CD.. It comes one directory back. CD\ It comes to the Root Directory. Copy Con Command: Purpose: Creates file to the console. Syntax: Copy con (drive:) (path) File Name. Ren Command: Purpose: To rename the file with new name. Syntax: Ren (drive:) (path) old file Name new file name. Del Command: Purpose: To delete the file from the directory. Syntax: Del (drive:) (path) File Name (\p) \p prompts for the confirmation before deleting each file.

4 RD Command: Purpose: To delete/remove the directory Syntax: Del (drive:) (path) File Name (\p) Copy command: Purpose: To copy the file from one directory to another. Syntax: copy (drive:) (path) source File Name (drive:) (path) destination directory. [\v;\y;\-y] \v: verifies the source files copying correctly to the destination directory or not. \y: Suppresses prompting before copying each existing destination file. \-y: Causes prompting before copying each existing destination file. cls command: Purpose: To clear the screen. Syntax: cls Date command: Purpose: Displays current date [mm:dd:yy] Syntax: Date Time command: Purpose: Displays current time [hh:mm:ss] Syntax: time Type command: Purpose: Types the contents of file. Syntax: Type (drive:) (path) File Name Dir command: Purpose: Displays directories and files. Syntax: Dir (drive:) (path) Directory name DIR tells you what files are on the disk, how big they are, and when they were created. DIR also tells how many files total are in the list, how much space those take and what free space remains. \p : Displays the directory listing page wise. \w: Displays the directory listing in wide format. \s: Displays the directory listing with directories, subdirectories and files.\ \l: Displays the directory listing in lower case format. \b: Displays the directory listing in bare format. [O switch]: Sorts directory listing in specified order. \on: Sorts directory listing on file name. \oe: Sorts directory listing on extension. \os : Sorts directory listing on file size. \od: Sorts directory listing on date and time. \og : Displays group directories first. [A switch]: Displays files with given attributes: \ar : Displays files with read only attribute. \aa : Displays files with archive attribute. \as : Displays files with system attribute. \ah : Displays files with hidden attribute.

5 Attrib Command: Purpose: To attributes to files. Syntax: attrib (drive:) (path) filename (+)(-) [R,A,S,H] Attribute: Identification of file. +: used to set the attributes. - : used to clear the attributes. R: Read only attribute. A: Archive attribute. S: System attribute. H: Hidden Attribute. Prompt command: Purpose: To change the appearance of command prompt. Syntax: Prompt [string] $$: To display $ sign. $n: Current drive. $g: Greater than sign. $l: Less than sign. $p: current drive & path. $v: DOS version. $b: Piping Symbol. $d: Current date. $t: Current time. $- : Leaves one line blank. Find Command: Purpose: Finds string in specified file. Syntax: find string (drive:) (path) filename.[\i, \c, \n, \v] \i: Ignores the case of string. \c: Counts the number of times string found. \n: Gives the string with line number. \v: Gives the line not containing the string. Sort Command: Purpose: To sort the contents of file. Syntax: sort< (drive:) (path) filename> \r: sorts the contents in reverse \ descending order. \+n: sorts the contents according to the character in column n. External Commands: Xcopy Command: Purpose: copies directories, sub directories and files into the specified directory. Syntax: xcopy (drive:) (path) source directory (drive) (path) destination directory Format command: Purpose: To create tracks and sectors onto drive. Syntax: format (drive:) Diskcopy command: Purpose: Copies contents of one disk to another disk. Syntax: diskcopy (drive1) (drive2).

6 Diskcomp command: Purpose: Compares the contents of two identical diskettes. Syntax:Diskcomp(drive1) (drive2). How to work with Sub Directories: The DOS directory structure can be thought of as a tree, with the master disk directory being called the root and subdirectories thought of as branches. The root is the hard disk's master directory. Subdirectories may contain any number of entries (until the disk is full). Pathnames: Subdirectory in the path is separated by a backslash (\). The single backslash at the beginning of the pathname indicates the root. All pathnames must originate in either the current directory or root. Tree: All directory paths and their relationships are called a tree. If you don't remember the various subdirectories (and optionally the files in them) DOS offers you a chance to see them with the TREE command: TREE d:/f This command lists all paths from the root on the disk. If you use the /f option, you will also see all files in each subdirectory. (Only the filenames are shown, not their size or creation date/time.) For a permanent record, press Control-PrtScr before issuing the TREE command and again after. Your printer will record all text scrolling past on the screen. Ankit Gupta ankitg1689@gmail.com