A multi-user operating system has
been designed for more than one user to access the computer at the same or
different time. It allows two or more users to run programs at the same time.
The OS of mainframes and minicomputers are multi-user systems. Examples are
UNIX, LINUX etc.
DOS (Disk
Operating System) was the first widely-installed operating system for personal
computers. It was the most popular before coming ms-windows os. It is developed
for the disk drives. It is a CUI based os. Its main function is to establish
the relationship between hardware and software. It also provides an executable
environment to the software inside the system. E.g. PC-DOS, MS-DOS, DR-DOS, Free-DOS, ROM-DOS and PTS-DOS.
etc.
MS-DOS is a
command based single user, single tasking operating system software which is an
extended version of CP/M. It was created for IBM PC and IBM compatible
computers. MS-DOS originally written by Tim Paterson and
introduced by Microsoft in
August 1981 and
was last updated in 1994 when
MS-DOS 6.22 was released.
EXTERNAL COMMANDS
· These are those commands which are not in-built in MS-DOS.
· They are stored on the system disk as program files.
· These commands are not loaded at the time of booting.
· They are only loaded to the memory when they are used.
· External commands are those which are not included in the interpreter.
· There is a need of an internal file in the computer to read external MS-DOS command.
· External command may vary from system to system. This means any two computers with same version of MS-DOS may have same internal commands, but may have different external commands.
· These are tree, xcopy, diskcopy, more, print etc.
Concept of File
A file is a
collection of related information stored on a disk. Each file is referred by a
unique name called file name. File names are divided into two parts, first part
is called primary file name and the second part is called the extension which
are separated by a period or dot.
Types of file
·
Program or executable file (.exe, .com, .bat)
·
Graphics file or picture files (.bmp, .jpg,
.gif)
·
Data file( .dat, /mdb)
·
Text file (.doc, .txt, .ini)
General rules for naming/
writing the file name:
·
File name can be up to eight characters.
·
File extension can be up to three characters.
·
File names must not contain: blank spaces,
commas, backslash, dot etc.
·
Never makes this
name of file: CLOCK$, CON, AUX, COM1, COM2,COM3, COM4, LPT1, LPT2, LPT3, NUL,
PRN etc
·
Blank spaces are not allowed in the mid of file
name.
·
File name must begin with alphabet or letter.
·
File name is combination of letters, digits and
special symbols.
·
Some special symbols are also used such as @, #,
$, %, ^, _, ~, {}, -, ‘, () etc
·
It is not case sensitive in most of the OS.
·
Examples are: Nepal.txt, kic.doc, lab.bmp,
list.xls etc
Extension
It helps us to
understand the file type. After the filename no need to type the extension
because extension is supplied by the software package automatically to identify
the application used.
Directory
A directory is a
partition place or table content of a disk which is used for storing files and
sub-directories. A directory contains the files with detail information such as
name, size, address, date of creation, last date of modification, etc.
There are two types of directories:
·
Root directory: - Root directory is the
main directory of disk which contains many other directories and files. It is
also called parent directory. Disks have at least one directory which creates
itself when a disk is to format that is called root directory. Root directory
is indicated by back slash (\).
·
Sub directory: - A sub directory is a
directory inside another directory. A sub directory is also called child
directory. Sub directory can contain other directories and files inside it.
Wild card characters
A wildcard is
a
symbol used
to replace or represent one or more characters in file name, extension,
character, directory, drive etc. it is used for quick execution of the DOS
commands. Basically, the wild cards are ‘?’ and ‘*’. The wild card characters
are:
·
*
-> represent a group of known
characters such as file name, extension
·
? -> Indicate any one character.
·
.* -> represent unknown extension.
·
*.* -> represent any unknown file name with any
extension.
·
^ -> represent control sign
·
>
-> represent a prompt component separator/ direction
·
/ -> adding options/ switch
·
\ -> represent a root directory and directory
separator
·
: -> represent a drive component
·
| -> Pipe line
Some examples of wild-card characters:
·
Dir*.doc :- display all files having doc
extension.
·
Dir r*.xls :- displays all files starting with r
and having xls extension.
·
Del*.chk :- delete all files having chk
extension.
·
TT?.exe :- Represents all typing tutor
application.
·
Dir/ON/P :- displays all files and directories
in ascending order page by page.
·
CD\ :- to return back from the existing
directory into the main prompt.
·
A: or C: :- changing drive.
·
C:\> :- Main prompt
·
Dir???.bas :- displays all files having three
character in filename and bas as extension
·
dir he??.*
:-. List any file that is four characters
long, begins with he, and has any extension. For example, help.txt, help.mp3,
and heck.jpg would all be matched.
·
rename
*.txt *.jpg :- Rename all
files in the current directory that end with the file extension .txt to .jpg.
For example, the file test.txt would become test.jpg.
·
del comp*.txt
:- Deleting files in MS-DOS that begin with comp and end with a .txt extension.
Definition of: DOS path name
The path name is used whenever it
is necessary to type in the location of a file rather than pointing to it with
the mouse. The path starts with the drive letter followed by the directory
hierarchy and ends with the file name itself.
pathname
|
Specifies a pattern, file or directory.
|
For example:
DRIVE
DIRECTORIES FILE NAME
This is often called the "full path name," which defines the entire
route, or path, to a specific file.
The following example is the full path name to the SALES.DBF file that resides
in the DBASE directory on the C: drive:
c:\dbase\sales.dbf
The full path to a file named BUDGET.WK1 in the root directory on the D: drive
looks like this:
d:\budget.wk1
Sometimes, you cannot tell whether a path name is a directory path or a full
path name to a file. The following example could be both. LETTER could be a
subdirectory attached to the WP directory, or it could be a document within the
WP directory.
c:\wp\letter
If LETTER was a document in the LETTER directory, its full path name would be:
c:\letter\letter
Filename
A filename (also written as two words, file
name) is a name used to uniquely identify
a computer file stored in a file system. Different file systems impose different restrictions on filename
lengths and the allowed characters within file-names.
A filename may include one or
more of these components:
·
host (or node or server) –
network device that contains the file
·
device (or drive) – hardware device or
drive
·
directory (or path) – directory tree
(e.g.,
/usr/bin, \TEMP, [USR.LIB.SRC],
etc.)
·
file – base name of the file
·
type (format or
extension) – indicates the content type of the
file (e.g. .txt, .exe, .COM, etc.)
·
version – revision or generation number of
the file
Booting
Booting is a
process of loading the system files (IO.SYS, COMMAND.COM and MSDOS.SYS) into
the memory from bootable disk like as HDD, CD, DVD, FDD etc.
Types of booting
a) Cold Booting: - A process of starting
the computer from off-state is known as cold booting. In cold booting period,
the computer can perform following tasks:
§
Read the RAM space.
§
Read the ROM instructions.
§
Checking all the internal components of the
computer system.
§
Loading the system files into main memory.
b)
Warm Booting: -
A process of restarting the computer from on-state is called warm booting. In
the warm booting period, the computer can perform following tasks:
§
No read the RAM space.
§
No read of the ROM instructions.
§
No checking internal parts of computer system.
§
Only, loading the system files into memory.
Note: - press ctrl+alt+del for reboot the computer only in
windows-95.
Remember:
The Minimum requirements for booting to start, we need at
least three files
a)
ms_dos.sys
b)
IO.SYS
c)
Command.com
In both files the ms_dos.sys file is a hidden file and the
Command.com is a regular file.
MS-DOS System files
a) IO.SYS:- It is a hidden file in the
root directory of the primary drive. This file provides the basic I/O
capability for the system, allowing it the ability to communicate with the
different peripheral.
§
It permanently resides in the memory as long as
the power is ON.
§
It interacts between ROM BIOS and call from the
MSDOS.SYS program.
§
It is always contains at least five device
drivers, used to control the operation of our keyboard, screen, printer, disk
controller and system clock.
§
Its final task is to load COMMAND.COM.
b) MSDOS.SYS:- it is also a hidden file in
the root directory sometime called the kernel for DOS. When an application
needs to access a device or peripheral, this file translates the request into
action that IO.SYS can perform.
§
This file interacts directly with application
programs and IO.SYS.
§
It acts as a bridge between application programs
and IO.SYS
c) COMMAND.COM: - it is the command
interpreter file. It can accept command from the user, launch programs and pass
this information to MSDOS.SYS.
§
It interprets the internal command of MSDOS
directly to the CPU and the internal command to the CPU after reading the
external command files.
§
It is also called command processor.
§
It also produces the DOS disk prompt, performs
error checking, and display error messages when system error are detected.
d) CONFIG.SYS: - It is a system configuration
file. It contains commands for configuring computer’s hardware components
(memory, keyboard, mouse, printer etc) and reserved space in memory for
processing of information.
§
When the computer is switched ON, it looks for a
file named CONFIG.SYS. if DOS finds that file, it configures the system
according to commands given in this file.
§
It contains two types of commands: configuration
command and device driver command.
§
Loading up device driver software.
§
Configuring files, buffers and application program.
§
Installing memory resident program.
e) AUTOEXC.BAT:- It is another
user-configuration text file that I used to set a system. It sets DOS prompt,
searches files for executable files and tart memory resident program and makes
our work convenient.
§
These commands are executed automatically in
sequence at the time of booting of computer since this file is executed
automatically at the time of booting of computer.
Drive and Drive letter
All the
secondary storage devices like floppy disk, hard disk and compact disk are
called drive.
All the storages are denoted by
different alphabets and letters followed by colon(J, which are called
drive letters.
Example
Drive Drive letter
Floppy Drive A: or B:
Hard Disk C: or D: or E: or F: etc (if
partitioned)
DOS Prompt
It is the main
gate of the MS-DOS, from where we can do any type of work. It is denoted by
A:\> or C:\> or D:\>, or E:\> etc.
Working or current directory
The directory
which is currently used read/ write process is called working directory or
current directory.
Windows
Windows is multi user; multitasking
and GUI based operating system which is developed by Microsoft Corporation,
USA. It allows a user to open multiple programs at a time in separate windows.
Nowadays, windows OS is used in PC, including home and business, desktops,
laptops, notebooks, media centers. Almost 90 % of all personal computers use
this system.
Features of Windows
OS
·
It is GUI based OS.
·
It is easier to learn and use.
·
It allows the user to work on a number of
applications simultaneously.
·
Failure to any application does not harm the
computer.
·
It has many built in programs.
·
It has fast processing capability.
·
It helps to run the multiple applications at a
time.
·
It is more user-friendly.
·
It is 32 bits, 64-bits and 86-bits OS.
·
It supports multiple numbers of i/o devices.
Choices of Operating System
DOS
Acronym for
“Disk Operating System”. DOS is a 16-bit, single-user operating system that
does not support multi-tasking. It is far easier to administer than UNIX, but
less powerful. Compared to graphical interfaces such as Windows and Mac OS X,
it's also not particularly user-friendly.
Microsoft Windows Operating
System
The Windows
operating system is developed and maintained by Microsoft, the company founded
by Bill Gates. The first version was released in 1985. Since then, it has grown
significantly, and it now dominates the market. Windows uses a graphical user interface to
make it easier for people to use their computers. The primary ways that people navigate are through icons on the desktop and the Start menu.
The Windows operating system,
like the Macintosh and Linux, allows people to manage files and run
software programs on desktop and laptop computers.
Open source
Open source refers
to a program or software in which the source code (the
form of the program when a programmer writes a program in a particular
programming language) is available to the general public for use and/or
modification from its original design free of charge. Open source code is
typically created as a collaborative effort in which programmers improve upon
the code and share the changes within the community. Example: unix, linux etc
UNIX
UNIX (pronounced
as YOO-niks) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Lab.
UNIX runs on many types of computers, including supercomputers, notebook PCs,
mainframes and minicomputers. Its main ability is that it works with so many
kinds of hardware.
Bell Labs distributed the
operating system in its source language form, so anyone who obtained a Copy could modify and
customize it for his own purposes. By the end of the 1970s, dozens of different
versions of UNIX were running at various sites.
Types of UNIX
There are many different versions of UNIX, although they share common
similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux,
and MacOS X.
Here in the School, we use Solaris
on our servers and workstations, and Fedora Linux on the servers and desktop
PCs.
The UNIX operating system
The UNIX operating system is made up of three parts; the
kernel, the shell and the programs.
The kernel
The kernel of UNIX is the hub of the operating system: it
allocates time and memory to programs and handles the file store and
communications in response to system calls.
The shell
The shell acts as an interface
between the user and the kernel. When a user logs in, the login program checks
the username and password, and then starts another program called the shell.
The shell is a command line interpreter (CLI). It interprets the commands the
user types in and arranges for them to be carried out. The commands are
themselves programs: when they terminate, the shell gives the user another
prompt (% on our systems).
Files and processes
Everything in UNIX is either a file or a process.
A process is an executing program identified by a unique PID
(process identifier).
A file is a collection of data. They are created by users
using text editors, running compilers etc.
Examples of files:
§
a document (report, essay etc.)
§
the text of a program written in some high-level
programming language
§
instructions comprehensible directly to the
machine and incomprehensible to a casual user, for example, a collection of
binary digits (an executable or binary file);
§
a directory, containing information about its
contents, which may be a mixture of other directories (subdirectories) and
ordinary files.
LINUX
Linux is a generic term that
commonly refers to Unix like computer operating system that use the Linux kernel. Linux is one of the most prominent
examples of free software and open source development; typically all the underlying source code can be used, freely modified, and redistributed by anyone.
Ubuntu, NepaLinux, User Linux etc are few examples of Linux distributions.
