BBA-I: Computer Applications for Business: Computer Network Types

Computer Network Types

Local Area Network

A computer network spanned inside a building and operated under single administrative system is generally termed as Local Area Network (LAN). Usually,LAN covers an organization’ offices, schools, colleges or universities. Number of systems connected in LAN may vary from as least as two to as much as 16 million.

LAN provides a useful way of sharing the resources between end users.The resources such as printers, file servers, scanners, and internet are easily sharable among computers.

Fig: Local Area Network (LAN)

LANs are composed of inexpensive networking and routing equipment. It may contains local servers serving file storage and other locally shared applications. It mostly operates on private IP addresses and does not involve heavy routing. LAN works under its own local domain and controlled centrally.

LAN uses either Ethernet or Token-ring technology. Ethernet is most widely employed LAN technology and uses Star topology, while Token-ring is rarely seen.

Metropolitan Area Network

The Metropolitan Area Network (MAN) generally expands throughout a city such as cable TV network. It can be in the form of Ethernet,Token-ring etc.

Metro Ethernet is a service which is provided by ISPs. This service enables its users to expand their Local Area Networks. For example, MAN can help an organization to connect all of its offices in a city.

Fig: Metropolitan Area Network (MAN)

Backbone of MAN is high-capacity and high-speed fiber optics. MAN works in between Local Area Network and Wide Area Network. MAN provides uplink for LANs to WANs or internet.

Wide Area Network

As the name suggests,the Wide Area Network (WAN) covers a wide area which may span across provinces and even a whole country. Generally, telecommunication networks are Wide Area Network. These networks provide connectivity to MANs and LANs. Since they are equipped with very high speed backbone, WANs use very expensive network equipment.

Fig: Wide Area Network (WAN)

WAN networks connect computers together over large physical distances, remotely connecting them over one huge network and allowing them to communicate even when far apart. The Internet is a WAN, and connects computers all around the world together.

BBA-I: Computer Applications for Business: Computer Network Topology

Computer Network Topology

A Network Topology is the arrangement with which computer systems or network devices are connected to each other. Topologies may define both physical and logical aspect of the network. Both logical and physical topologies could be same or different in a same network.

Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.

Types of Network Topology:

Bus Topology:

Fig: Bus Topology

In case of Bus topology, all devices share single communication line or cable.Bus topology may have problem while multiple hosts sending data at the same time.

It is one of the simple forms of networking where a failure of a device does not affect the other devices. But failure of the shared communication line can make all other devices stop functioning.

Both ends of the shared channel have line terminator. The data is sent in only one direction and as soon as it reaches the extreme end, the terminator removes the data from the line.

Advantages of Bus Topology

1. It is cost effective.
2. Cable required is least compared to other network topology.
3. Used in small networks.
4. It is easy to understand.
5. Easy to expand joining two cables together.

Disadvantages of Bus Topology

1. Cables fails then whole network fails.
2. If network traffic is heavy or nodes are more the performance of the network decreases.
3. Cable has a limited length.
4. It is slower than the ring topology.

Star Topology

All hosts in Star topology are connected to a central device, known as hub device, using a point-to-point connection. That is, there exists a point to point connection between hosts and hub.

Fig: Star Topology

As in Bus topology, hub acts as single point of failure. If hub fails, connectivity of all hosts to all other hosts fails. Every communication between hosts, takes place through only the hub.Star topology is not expensive as to connect one more host, only one cable is required and configuration is simple.

Advantages of Star Topology

1. Fast performance with few nodes and low network traffic.
2. Hub can be upgraded easily.
3. Easy to troubleshoot.
4. Easy to setup and modify.
5. Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

1. Cost of installation is high.
2. Expensive to use.
3. If the hub fails then the whole network is stopped because all the nodes depend on the hub.
4. Performance is based on the hub that is it depends on its capacity.

Ring Topology

In ring topology, each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send message to a host which is not adjacent to it, the data travels through all intermediate hosts. To connect one more host in the existing structure, the administrator may need only one more extra cable.

Failure of any host results in failure of the whole ring.Thus, every connection in the ring is a point of failure. There are methods which employ one more backup ring.

Advantages of Ring Topology

1. Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
2. Cheap to install and expand

Disadvantages of Ring Topology

1. Troubleshooting is difficult in ring topology.
2. Adding or deleting the computers disturbs the network activity.
3. Failure of one computer disturbs the whole network.

Mesh Topology

In this type of topology, a host is connected to one or multiple hosts.This topology has hosts in point-to-point connection with every other host or may also have hosts which are in point-to-point connection to few hosts only.

Fig: Mesh Topology

Advantages of Mesh Topology

1. Each connection can carry its own data load.
2. It is robust.
3. Fault is diagnosed easily.
4. Provides security and privacy.

Disadvantages of Mesh Topology

1. Installation and configuration is difficult.
2. Cabling cost is more.
3. Bulk wiring is required.

BBA-I: Computer Applications for Business: Computer Networking

What is a Computer Network?

A computer network is a system in which multiple computers are connected to each other to share information and resources.

A computer network is a set of computers connected together for the purpose of sharing resources. The most common resource shared today is connection to the Internet. Other shared resources can include a printer or a file server. The Internet itself can be considered as a computer network.

A computer network is a set of connected computers. Computers on a network are called nodes. The connection between computers can be done via cabling, most commonly the Ethernet cable, or wireless through radio waves. Connected computers can share resources, like access to the Internet, printers, file servers, and others. A network is a multipurpose connection, which allows a single computer to do more.

Fig: A Computer Network

Characteristics of a computer network

·        Share Resources from one computer to another

·        Create files and store them in one computer, access those files from the other computer(s) connected over the network

·        Connect a printer, scanner, or a fax machine to one computer within the network and let other computers of the network use the machines available over network.

Following is the list of hardware's required to setup a computer network/Components/Tools for Networking:-

• Network Cables
• Distributors
• Routers
• Internal Network Cards
• External Network Cards

Network Cables

Network cables are used to connect computers. The most commonly used cable is Category 5 cable RJ-45.

Distributors

A computer can be connected to another one via a serial port but if we need to connect many computers to produce a network, this serial connection will not work. The solution is to use a central body to which other computers, printers, scanners etc. can be connected and then this body will manage or distribute network traffic.

Router

A router is a type of device which acts as the central point among computers and other devices that are part of a network. A router is equipped with holes called ports and computers and other devices are connected to a router using network cables. Now-a-days router comes in wireless modes using which computers can be connected without any physical cable.

Network Card

Network card is a necessary component of a computer without which a computer cannot be connected over a network. It is also known as network adapter or Network Interface Card (NIC). Most branded computers have network card pre-installed. Network cards are of two types : Internal and External Network Cards.

INTERNAL NETWORK CARDS

Motherboard has a slot for internal network card where it is to be inserted. Internal network cards are of two types in which first type uses Peripheral Component Interconnect (PCI) connection while the second type uses Industry Standard Architecture (ISA). Network cables are required to provide network access.

EXTERNAL NETWORK CARDS

External network cards come in two variants : Wireless and USB based. Wireless network card need to be inserted into the motherboard but no network cable is required to connect to network.

BBA-I- Computer Applications for Business: LINUX Operating System

Operating System - Linux

Linux is one of popular version of UNIX operating System. It is open source as its source code is freely available. It is free to use. Linux was designed considering UNIX compatibility. Its functionality list is quite similar to that of UNIX.

Following are some of the important features of Linux Operating System.

1. ·        Portable − Portability means software can works on different types of hardware in same way. Linux kernel and application programs support their installation on any kind of hardware platform.
2. ·        Open Source − Linux source code is freely available and it is community based development project. Multiple teams work in collaboration to enhance the capability of Linux operating system and it is continuously evolving.
3. ·        Multi-User − Linux is a multiuser system means multiple users can access system resources like memory/ ram/ application programs at same time.
4. ·    Multiprogramming − Linux is a multiprogramming system means multiple applications can run at same time.
5. ·        Hierarchical File System − Linux provides a standard file structure in which system files/ user files are arranged.
6. ·        Shell − Linux provides a special interpreter program which can be used to execute commands of the operating system. It can be used to do various types of operations, call application programs. etc.'
7.     Security − Linux provides user security using authentication features like password protection/ controlled access to specific files/ encryption of data.

Architecture

The following illustration shows the architecture of a Linux system −

The architecture of a Linux System consists of the following layers −

• ·        Hardware layer − Hardware consists of all peripheral devices (RAM/ HDD/ CPU etc).
• ·     Kernel − It is the 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. The shell takes commands from the user and executes kernel's functions.
• ·        Utilities − Utility programs that provide the user most of the functionalities of an operating systems.

Advantages of LINUX Operating System:

1.      Cost – The most obvious advantage of using Linux is the fact that it is free to obtain as it is an open and free software.

2.      Security – In line with the costs, the security aspect of Linux is much stronger, powerful and reliable.

3.      Choice (Freedom) – The power of choice is a great Linux advantage. With Linux, you have the power to control just about every aspect of the operating system.

4.      Software – There are so many software choices when it comes to doing any specific task. Regular users and programmers contribute applications all the time. In addition, software on Linux tends to be packed with more features and greater usability than software on Windows. Best of all, the vast majority of Linux software is free and open source.

5.      Hardware – Linux is perfect for those old computers with barely any processing power or memory.

Disadvantages of Linux Operating System:

1.    Understanding – Becoming familiar with the Linux operating system requires patience as well as a strong learning curve.

2.    Compatibility – Because of its free nature, Linux is sometimes behind the curve when it comes to brand new hardware compatibility.

BBA-I_Computer Applications for Business: UNIX Operating System

What is UNIX?

The UNIX operating system is a set of programs that act as a link between the computer and the user.

The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel.

Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel.

Features of UNIX

·         Multiuser Capability

·         Multitasking Capability

·         Communication

·         Security

·         Portability

MULTI USER CAPABILITY:

UNIX Operating System supports many users to use the resources from different computers connected to it at the same time. There need not be operating system installed on all of them. A single computer with UNIX operating system can help in running all of them at the same time.

MULTI TASKING CAPABILITY:

It is capable of carrying out more than one job at the same time. It allows user to type in a program in its editor while  it simultaneously   executes  some other commands  like  sort,  copy  a huge file.

The later job is performed in the background while in the foreground uses the editor or takes a directory listing or anything else.

This is managed by dividing  the  CPU  time  intelligently between all process being carried out .Depending on the  priority of the task, the OS    approximately  allots   small time slots  (of  the order of milliseconds or  microseconds)  to  each foreground and background task.

COMMUNICATION:

The communication may be within the network of a single main  computer or between two or more such computer networks. The users can easily  exchange  mail,  data  programs    through   such networks. Distance  posses  no barrier to passing  information  or messages to and fro.

SECURITY:

Unix has 3  inbuilt features for protecting data:-

i) Assign passwords and login name to users area.

ii) Provide read, write and execute permission to each file.

iii)Encrypt files into an unreadable format, and decrypting the file is also possible.

PORTABILITY:

Unix is a highly portable OS. It can be ported to a variety of hardware platforms. It is the only system which has been ported across various hardware platforms of major vendors such as IBM, DEC, HP and SUN. Most OSs are written for one specific machine or platform only.

Advantages of Unix

-  Unix is more flexible and can be installed on many different types of machines, including main-frame computers, supercomputers and micro-computers.

- Unix is more stable and does not go down as often as Windows does, therefore requires less administration and maintenance.

- Unix has greater built-in security and permissions features than Windows.

- Unix possesses much greater processing power than Windows.

- Unix is the leader in serving the Web. About 90% of the Internet relies on Unix operating systems running Apache, the world's most widely used Web server.

- Software upgrades from Microsoft often require the user to purchase new or more hardware or prerequisite software. That is not the case with Unix.

Disadvantages of Unix:

Interface

·         The traditional interface for the Unix operating system is command line based, and this command line shell interface may be hostile to the casual user. Unix was developed for use by programmers and serious computer users rather than casual users. A graphical user interface (GUI) is also available, but the traditional Unix interface is command line only.

Special Commands

·         Commands required by the command line interface often make use of cryptic naming schemes, and do not give much information to notify a user of what they are doing. Many commands in the Unix interface require the use of special characters. Small, normally insignificant typos can have much greater effects and unexpected results on Unix machines.

Not User-Friendly:

·         Not as user-friendly or easy to learn for the average person as windows is.

BBA-I CAB: MS-DOS & Windows Operating system & Features

Source: Computer Applications for Business Thakur Publications

BBA-I_CAB_Operating System

An Operating System (OS) is an interface between a computer user and computer hardware. An operating system is a software which performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers.

An operating system or OS is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer operating system, a computer and software programs would be useless. The picture is an example of Microsoft Windows XP, a popular operating system and what the box may look like if you were to visit a local retail store to purchase it.

When computers were first introduced, the user interacted with them using a command line interface, which required commands. Today, almost every computer is using a Graphical User Interface (GUI) operating system that is much easier to use and operate.

Some popular Operating Systems include MS-DOS, Windows, UNIX, Linux.

Fig: Operating System

Following are some of important functions of an operating System.

• Memory Management
• Processor Management
• Device Management
• File Management
• Security
• Control over system performance
• Job accounting
• Error detecting aids
• Coordination between other software and users

Memory Management

Memory management refers to management of Primary Memory or Main Memory. Main memory is a large array of words or bytes where each word or byte has its own address.

Main memory provides a fast storage that can be accessed directly by the CPU. For a program to be executed, it must in the main memory. An Operating System does the following activities for memory management:

1. ·        Keeps tracks of primary memory, i.e., what part of it are in use by whom, what part is not in use?
2. ·        In multiprogramming, the OS decides which process will get memory when and how much.
3. ·        Allocates the memory when a process requests it to do so.
4. ·        De-allocates the memory when a process no longer needs it or has been terminated.

 

 Processor Management

In multi programming environment, the OS decides which process gets the processor when and for how much time. This function is called process scheduling. An Operating System does the following activities for processor management −

1. ·        Keeps tracks of processor and status of process. The program responsible for this task is known as traffic controller.
2. ·        Allocates the processor (CPU) to a process.
3. ·        De-allocates processor when a process is no longer required.

Device Management

An Operating System manages device communication via their respective drivers. It does the following activities for device management −

1. ·        Keeps tracks of all devices. Program responsible for this task is known as the I/O controller.
2. ·        Decides which process gets the device when and for how much time.
3. ·        Allocates the device in the efficient way.
4. ·        De-allocates devices.

File Management

A file system is normally organized into directories for easy navigation and usage. These directories may contain files and other directions.

An Operating System does the following activities for file management −

1. ·        Keeps track of information, location, uses, status etc. The collective facilities are often known as file system.
2. ·        Decides who gets the resources.
3. ·        Allocates the resources.
4. ·        De-allocates the resources.

Other Important Activities

Following are some of the important activities that an Operating System performs −

1. ·        Security − By means of password and similar other techniques, it prevents unauthorized access to programs and data.
2. ·        Control over system performance − Recording delays between request for a service and response from the system.
3. ·        Job accounting − Keeping track of time and resources used by various jobs and users.
4. ·        Error detecting aids − Production of dumps, traces, error messages, and other debugging and error detecting aids.
5. ·        Coordination between other software and users − Coordination and assignment of compilers, interpreters, assemblers and other software to the various users of the computer systems.