Download Unit 2 - NIST NACOL

Software
A Set Of Program Written For A Computer To Perform A Particular Task Is Called Software. Software Is A
Computer Programs That Tells The Computer What To Do And How To Do. Hardware Alone Cannot Do
Anything Without Software. Software Is Used To Create The Interface Between User And Hardware.
Windows OS, Antivirus, Microsoft Office, Adobe Photoshop Are Some Example Of Software.
The Software Are Classified Into Two Parts:
(A) System Software:
It Is The Computer Software Designed To Operate The Computer Hardware And To Provide A Platform
For Running Application Software. It Helps On Running Computer Hardware And The Computer System.
It Is Responsible For Resource Management, Memory Management, File Management, Task Scheduling,
Software Repairing, Language Translation And System Maintenance. It Is Use To Allow The User To
Communicate With The Hardware.
The System Software Can Be Sub-Divided As Follows:
I.
Operating System:
It Is Used To Manage The Various Resources And Overall Operation Of The Computer System.
Ii.
Translator (Language Processor)
Translator Is A Computer Programs That Convert The Program Written In Other Language Into
An Equivalent Machine Language Program Before Executing Them.
Iii.
Utility Software
It Is A System Support Software Or Service Program, Which Provide Useful Services To The User
Of The Computer.
(B) Application Software:
The User Oriented Software Which Is Particularly Designed To Solve The Problem Of User. The
Application Software May Be Used For Official Purpose, Engineering Design, Teaching Aid And So On.
MS-Word, Word Perfect, Ms-Excel, Ms Power Point, Accounting Software, Banking Software Are Some
Example Of Application Software.
The Application Software Can Be Sub-Divided As Follows:
I.
Packaged Software
Packaged Software Is That Software Which Is Generalized Set Of Programs Designed And
Developed For General Purpose.
Ii. Tailored Software
It Is A Software Designed To Meet The Specific Requirements Of An Organization Or Individuals.
The Difference Between System Software And Application Software:
System Software
1 It Is Hardware Oriented Software.
2 It Is Developed To Operate Or Manage The
Hardware Component
3 It Is Usually Provided By The Hardware
Developer Along With The Hardware.
4 It Is Either Cheaper Or Provided In Free Of
Cost.
5 A Computer Cannot Be Operated Without
System Software.
6 For Developing System Software, User
Should Have Expert Knowledge
7 System Software Runs Independently.
8 It Is Of Three Types: Operating System,
Language Processor, Utility Software
9 Example: Windows XP, Linux
Application Software
1 It Is User-Oriented Software.
2 It Is Developed To Solve The Particular Problem
Of The User Or To Make The User's Task Easier.
3 It Is Usually Not Provided By The Hardware
Developer, User Has To Add As Per Need.
4 It Is Usually Expensive.
5 A Computer Can Runs Without Application
Software
6 Application Software Can Be Developed Without
Having The Knowledge Of Computer Hardware.
7 Application Can't Run Without The Present Of
The System Software.
8 It Is Of Two Types: Tailored Software, Packaged
Software
9 Example: Adobe, Microsoft Word, Excel Etc.
OPERATING SYSTEM
An Operating System is system software, which is set of specialized programs that are used to control
the resources of a computer system. It is an organized set or collection of software that controls the
overall operation of the computer system and provides an environment where the user can execute the
programs in appropriate and efficient manner.
Some of its major purposes are :
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It act as an intermediary between programs and computer hardware.
Operating system loads program in the memory when power is turned on.
It manages data tracks of files and memory such as primary, secondary etc.
It manages scheduling process
It allows user to share data and software among themselves.
Types of Operating System
Based on Processing
Multiprogramming OS:
A multiprogramming technique is used in the multi-user environment, it is the technique in which multiple
users programs are executed simultaneously by single processor or CPU. Multiprogramming means when
two or more programs are provided to the CPU for processing, or loaded into the internal storage of CPU
at the same instant. From the loaded programs once the portion of one program is executed, and then a
portion of another program is executed and so on. Thus multiprogramming refers to concurrent execution
of several programs.
Multitasking OS:
A multitasking OS allows more than one program to run concurrently mainly in a single user system.
Multitasking computer are capable of executing several tasks or programs at the same time. For executing
several task tasks it can be single or multiprocessing system.
Multiprocessing OS:
A multiprocessing system has more than one processor (cpu), linked together in a coordinated way. A
multiprocessing OS is one, which supports running a program in more than one central processing unit
(CPU). Server System and super servers are specially designed to supports multiple processors. UNIX is
commonly used multiprocessing OS. Multiprogramming and multiprocessing are not the same concepts.
Multiprogramming involves concurrent execution of two or more programs by a single CPU, whereas
multiprocessing involves two or more processors for controlling in different activities or execution of
many programs / instructions simultaneously.
Batch Processing OS:
In batch processing environment, it requires grouping of similar jobs, which consists of programs, data
and system commands. It is also known as offline processing. This type of processing is suitable in
programs with large computation time with no need of user interaction or involvement. Users need not
wait while the job is being processed. They can submit their programs to operators and collect them later.
Which means, the jobs are entered, stored on a disk in a batch or queue, and is executed one after another
under the control of the OS.
Online Processing OS:
In online processing method, transactions are processed as soon as it happened and at the place of
origin. It is quite simple compared to real time processing. It this type of processing OS, user can interact
or provide inputs during processing as well. The output is provided back to the users as soon as the
processing is completed. It is the popular processing technique at present.
Real Time OS:
Real time processing method is one that controls environment by receiving data processing them and
taking action or retuning result sufficiently quickly to affect the functioning of the environment at that
time. It is an online processing system, in which the processing time is critical. The entire processing task
has to be completed in the predefined time. The term real time refers to the technique of updating files
with the transaction data immediately after the event which it relates, occurs.
ON THE BASIS of USER INTERFACE
GUI Operating System:
Short for Graphical User Interface, a GUI operating system contains graphics and icons and is commonly
navigated by using a computer mouse. It takes advantage of the computer's graphic capabilities to
make the program easier to use. Well-designed graphical user interfaces can free the user from learning
complex command languages.
Basic Components:
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Pointer
Icons
Desktop
Windows
Menus
Folders
CUI based OS
In a character/command driven system to communicate with the computer, the user has to instruct the
computer in special commands (words). DOS is a very commonly used command driven user interface.
The main advantage of this interface is that they can be quick to use as long as the user knows the correct
commands. Pointing devices like mouse, joystick, trackball, track pad are not recognized with CUI based
OS. Usually CUI based OS are 8 or 16 bit OS.
FUNCTIONS OF Operating System
Process Management
The CPU executes a large number of programs. While its main concern is the execution of user programs,
the CPU is also needed for other system activities. These activities are called processes. A process is a
program in execution. Typically, a batch job is a process. A time-shared user program is a process. A system
task, such as spooling, is also a process. For now, a process may be considered as a job or a timeshared
program, but the concept is actually more general. In general, a process will need certain resources such
as CPU time, memory, files, I/O devices, etc., to accomplish its task. These resources are given to the
process when it is created. In addition to the various physical and logical resources that a process obtains
when it is created, some initialization data (input) may be passed along. We emphasize that a program by
itself is not a process; a program is a passive entity. It is known that two processes may be associated with
the same program; they are nevertheless considered two separate execution sequences. The operating
system is responsible for the following activities in connection with processes managed.
 The creation and deletion of both user and system processes
 The suspension and resumption of processes.
 The provision of mechanisms for process synchronization
 The provision of mechanisms for deadlock handling.
Memory Management
Memory is central to the operation of a modern computer system. Memory is a large array of words or
bytes, each with its own address. Interaction is achieved through a sequence of reads or writes of specific
memory address. The CPU fetches from and stores in memory. In order for a program to be executed it
must be mapped to absolute addresses and loaded in to memory. In order to improve both the utilization
of CPU and the speed of the computer's response to its users, several processes must be kept in memory.
The operating system is responsible for the following activities in connection with memory management.
 Keep track of which parts of memory are currently being used and by whom.
 Decide which processes are to be loaded into memory when memory space becomes available.
 Allocate and de-allocate memory space as needed.
Secondary Storage Management
The main purpose of a computer system is to execute programs. These programs, together with the data
they access, must be in main memory during execution. Since the main memory is too small to
permanently accommodate all data and program, the computer system must provide secondary storage
to backup main memory. Most modem computer systems use disks as the primary on-line storage of
information, of both programs and data. Most programs, like compilers, assemblers, sort routines, editors,
formatters, and so on, are stored on the disk until loaded into memory, and then use the disk as both the
source and destination of their processing. Hence the proper management of disk storage is of central
importance to a computer system. There are few alternatives. Magnetic tape systems are generally too
slow. In addition, they are limited to sequential access. Thus tapes are more suited for storing infrequently
used files, where speed is not a primary concern. The operating system is responsible for the following
activities in connection with disk management
 Free space management
 Storage allocation
 Disk scheduling
One of the purposes of an operating system is to hide the peculiarities of specific hardware devices from
the user. For example, in UNIX, the peculiarities of Input/output devices are hidden from the bulk of the
operating system itself by the INPUT/OUTPUT system. The Input/output system consists of:
 A buffer caching system
 A general device driver code
 Drivers for specific hardware devices.
Only the device driver knows the peculiarities of a specific device.
File Management
File management is one of the most visible services of an operating system. Computers can store
information in several different physical forms; magnetic tape, disk, and drum are the most common
forms. Each of these devices has it own characteristics and physical organization. For convenient use of
the computer system, the operating system provides a uniform logical view of information storage. The
operating system abstracts from the physical properties of its storage devices to define a logical storage
unit, the file. Files are mapped, by the operating system, onto physical devices. A file is a collection of
related information defined by its creator. Commonly, files represent programs (both source and object
forms) and data. Data files may be numeric, alphabetic or alphanumeric. Files may be free-form, such as
text files, or may be rigidly formatted. In general files are a sequence of bits, bytes, lines or records whose
meaning is defined by its creator and user. It is a very general concept. The operating system implements
the abstract concept of the file by managing mass storage device, such as tapes and disks. Also files are
normally organized into directories to ease their use. Finally, when multiple users have access to files, it
may be desirable to control by whom and in what ways files may be accessed. The operating system is
responsible for the following activities in connection with file management:
 The creation and deletion of files
 The creation and deletion of directory
 The support of primitives for manipulating files and directories
 The mapping of files onto disk storage.
 Backup of files on stable (non volatile) storage.
Protection System
The various processes in an operating system must be protected from each other’s activities. For that
purpose, various mechanisms which can be used to ensure that the files, memory segment, CPU and other
resources can be operated on only by those processes that have gained proper authorization from the
operating system. Protection refers to a mechanism for controlling the access of programs, processes, or
users to the resources defined by a computer controls to be imposed, together with some means of
enforcement. An unprotected resource cannot defend against use (or misuse) by an unauthorized or
incompetent user.
Networking
A distributed system is a collection of processors that do not share memory or a clock. Instead, each
processor has its own local memory, and the processors communicate with each other through various
communication lines, such as high speed buses or telephone lines. Distributed systems vary in size and
function. They may involve microprocessors, workstations, minicomputers, and large general purpose
computer systems. The processors in the system are connected through a communication network, which
can be configured in the number of different ways. The network may be fully or partially connected. The
communication network design must consider routing and connection strategies, and the problems of
connection and security. A distributed system provides the user with access to the various resources the
system maintains. Access to a shared resource allows computation speed-up, data availability, and
reliability. Command Interpreter System.
LINUX
Linux is a free and open-source operating system developed by Linus Torvalds and friends that was first
announced August 25, 1991. The Linux kernel runs on numerous different platforms including the Intel
and Alpha platform and is available under the GNU General Public License.
The system can be distributed, used, and expanded free of charge. In this way, developers have access to
all the source codes, thus being able to integrate new functions or to find and eliminate programming
bugs quickly. Thereby drivers for new adapters (SCSI controller, graphics cards, etc.) Can be integrated
very rapidly.
Linux may be obtained in two different ways. All the necessary components can be downloaded free of
charge from the Internet, which means an operating system can be assembled for almost nothing. An
alternative is to use a so-called distribution, which is a Linux variation offered by many companies. They
include a wide range of applications and full programs that significantly simplify the installation of Linux.
Presently, Linux is successfully being used by several millions of users worldwide. The composition of users
varies from private users, training companies, universities, research centers, and companies.
Linux System Architecture is consists of following layers:
Hardware Layer: Hardware consists of all peripheral devices (RAM/ HDD/ CPU etc)
Kernel: Core Component of Operating System, interacts directly with hardware provides low level services
to upper layer components.
Shell: An interface to Kernel, hiding complexity of kernel's functions from users. Takes commands from
user and executes kernel's functions.
UNIX
Coined by Brian Kernighan, Unix or UNIX (not an acronym) is an operating system developed by members
of the MULTICS team at the Bell Laboratories starting in the late 1960's, many who also help create C.
Today, Unix is not just the work of a couple of programmers; organizations, institutes, and other
individuals have contributed significant additions to Unix and its variants, making it a widely used and
popular operating system.
UNIX is primarily a command line operating system with additional applications such as X-Window to give
a graphic oriented operating system similar to Windows. Since Unix is often used from the command line,
there are various shells. A shell is a large add-on or modification of the Unix operating system, to
determine the shell you can type echo the Unix prompt.
Is it Unix or UNIX in all caps?
When first introduced, UNIX was a trademark of Bell Laboratories (AT&T), which is now owned by The
Open Group, who obtained the trademark in 1993. Today, Unix and UNIX are accepted as correct and
interchangeable when referring to the operating system. However, if you are referring to the trademark,
it would be more appropriate to use UNIX instead of Unix.
Windows
When referring to an operating system, Windows or win is an operating environment created by
Microsoft that provides an interface known as Graphical User Interface (GUI) for computers. Windows
eliminates the need to memorize commands for the command line (MS-DOS), by using a mouse to
navigate through menus, dialog boxes, buttons, tabs, and icons.
Microsoft Windows was first introduced with version 1.0 on November 10, 1983. Since its release, there
have been over a dozen versions of Windows. The most current version of Windows for end users is
Windows 10.
MAC
The Mac OS is an operating system that was designed for the Apple Macintosh computer. It was developed
by Apple Inc., who also created Apple I, as well as a number of other more modern products including
the ipod, iphone, and ipad. The main competition to the Mac OS is the Windows operating system, the
most popular OS by a large margin.
Historical Information
The first version of the Mac OS, part of the "Classic" Mac OS series, was originally released in the mid1980s. It did not possess a command line and could only run one application at a time. The first version of
the Macintosh operating system to be named "Mac OS" was version 7.6, the most recent version is
called Mac OS X.
Important Questions:
1. Define the terms network and data communication. Explain basic components of
communication system.
2. How can you categorize computer networks? Explain each type of computer network in detail.
3. What is mean by network architecture? Explain each peer to peer and client server network
architecture in detail.
4. What are the mode of data transmission? Explain each type of mode with suitable example.
5. What is meant by wireless network? Explain benefits of wireless networks in your own words.
6. How optical fiber is different from other guided media? Explain structure and working of optical
fiber.