Microsoft Software

Lecturer: Jing Liu

Email: [email protected]

Homepage: http://see.xidian.edu.cn/faculty/liujing

Microsoft Software

  Personal computers are becoming increasingly powerful, versatile and popular among organizations and individuals alike not because of reduction in their cost and increase in memory size but primarily due to the tremendous power and variety of software available. In fact, it is the software that makes a computer useful as well as user-friendly. Although there are a number of software vendors in the market, the main driving force behind the software revolution is the Microsoft Corporation.

Microsoft Software

  The first major software project of Microsoft Corporation was the development of an operating system known as Disk Operation Systems (DOS) for the original IBM personal computer in the year 1980. Although originally seen as a supplier of operating systems, Microsoft went on to develop a variety of successful application packages, thus becoming a leading software company in the world. Microsoft today has a suite of software packages that would meet many of the standard applications requirements of most organizations. This software suite, popularly known as Microsoft Office, includes the following application packages:

Microsoft Software

     Microsoft Word: Developed in 1983, it provides powerful tools for creating and manipulating word processing documents.

Microsoft Excel: Developed in 1985, it enables to create detailed spreadsheets for viewing and collaboration.

Microsoft PowerPoint: Developed in 1988, it provides a complete set of tools for creating presentations.

Microsoft Publisher: Developed in 1991, it helps in publishing materials, such as news letters, brochures and catalogs Microsoft Access: Developed in 1912, it gives powerful tools for creating and managing databases.

MS Word System

   MS Word is an application software that can be used to create, edit, save and print personal as well as professional documents in a very simple and efficient manner. It is mainly designed for word processing, so it is also referred as the word processing program.

MS Word is not the only word processing program available in the market. There are many other word processing applications available, such as Open Office Writer and Google Docs. For working in MS Word, we need to install MS Office in a computer system. After installing MS Office, we can start MS Word using Start menu.

MS Word System

Major components on the GUI of MS Word:  Title bar: It is a horizontal bar at the top of the window that displays the name of the currently opened MS Word document. By default, MS Word assigns names to new documents as Document1, Document2, Document3 and so on. However, we can also save our document with some other name of our choice.

 Menu bar: It is located right below the title bar. The Menu bar is used to house a set of commands that can be used to perform various operations such as opening a file, closing a file and creating a table.  Toolbar: It is located right below the menu bar. A number of toolbars are provided in MS Word for a quick and easy access to the various commands housed in the Menu bar.

MS Word System

 Document window: It is the actual area in the MS Word window where we can enter text and draw graphics. The document windows of MS Word can also be considered as a text editor because you can edit and apply different types of formatting to the text in this window.

 Status bar: It is located at the bottom of the MS Word window. The status bar provides some helpful information related to the document that we are currently working with. The information provided by the status bar includes:      Total number of pages in the document Page number of the active page Line number of the line of text where the cursor is currently positioned Column number of the character in the line of text where the cursor is currently positioned Status of various modes such as track mode, extend selection mode and overtype mode

MS Word System

 Scroll bar: The term scroll bar usually refers to the horizontal and the vertical bars placed at the right and the bottom of the MS Word windows. These bars allow the user to view those portions of the document that cannot fit on the screen at one time.  Ruler: It is located below the toolbars. The ruler bar in MS Word is used to set the alignment for the content in the document. If the ruler bar is not displayed in the MS Word window, then we can make it visible by selecting View->Ruler.

MS Word System - Menu Bar

   File menu: It contains a set of commands that can be used to perform various file handling operations. The file handling operations in MS Word are usually known as document handling operations. The various operations that can be performed using the options available in the File menu are opening a new document, opening an existing document, saving the current document, printing the current document, etc.

Edit menu: It contains a set of commands that can be used to perform various operations related to content editing and manipulation. The various operations that we can perform using the options available in the Edit menu are copying the currently selected text to clipboard, moving the currently selected text to some other location in the currently opened document, pasting the text from clipborad to the currently opened document, deleting the selectee text, tec.

View menu: It contains a set of commands that can be used to display the document in different views. The different views available in MS Word are Normal, Web Layout, Print Layout, Document Map, Full Screen and Zoom. Apart from changing the view of a document , we can also perform various other tasks using the View menu like displaying or hiding the toolbar, setting the header and footer for a document and displaying or hiding the rulers.

MS Word System - Menu Bar

 Insert menu: It contains a set of commands that can be used to insert various objects such as clip art, auto shapes, organization chart, word art and text box in a document to make it more attractive. Apart from these objects we can also insert date and time, page numbers, symbols, page break and column break in the document.

 Format menu: It contains a set of commands that can be used to alter the look and layout of the content present in the document. The various tasks that can be performed using the options available in the Format menu are changing the font type, font color, font size and font style of the selected text, indenting a paragraph, inserting bullets and numbering in the document, etc.

 Tools menu: It contains a set of commands that can be used to perform advanced operations in the MS Word document. The various tasks that can be performed using the options available in the Tools menu are checking and correcting spelling and grammatical mistakes, counting the number of words and characters, protecting a document and using mail merge, etc.

MS Word System - Menu Bar

 Table menu: It contains a set of commands that can be used to perform various operations related to the creation , modification and deletion of tables in a document.

 Windows menu: It contains a set of commands that can be used to perform various tasks related to the active windows in which we are working. Using his menu, we can open a new window containing the same content as the active window, split the active window into different panes and arrange all the opened document into separate windows in such a manner hat all the windows can be viewed at the same time by the user.

 Help menu: It assists the user by providing information related to MS Word from various sources such as Office Assistant tool and Microsoft Office Web site etc.

MS Word System - Toolbar

The three most commonly used toolbars in MS Word are as follows:  Standard toolbar: It provides quick access to the various operations related to the file handling and content editing and manipulation. If the Standard toolbar is not visible in the MS Word window, then we need to select View-> Toolbars -> Standard to make it visible.

 Formatting toolbar: It is used to perform various operations related to the look and the layout of the document content. Using the icons available on this toolbar, we can change the font size, style and color of the selected text, align the selected text to the left, center or right of the screen, create numbered and bulleted list, etc. If the Formatting toolbar is not visible in the MS Word window, then we need to select View -> Toolbars -> Formatting to make it visible.

 Drawing toolbar: It is located at the bottom of the screen just above the status bar. Using the different icons available on the drawing toolbar, we can draw and manipulate different types of graphics in a document. The various shapes that we can draw using the drawing toolbar are line, rectangle, oval, etc. We can also insert clip art, word art and pictures in the document using this toolbar. If the Drawing toolbar is not visible in the MS Word window, then we need to select View -> Toolbars -> Drawing to make it visible.

MS Word System

 The following are the key operations that we can perform in MS Word:      Creating a document Saving a document Editing a document Formatting a document Printing a document

MS Excel System

 MS Excel is an application program that allows us to create spreadsheets, which are represented in the form of a table containing rows and columns.  The horizontal sequence in which the data is stored is referred to as a row. The vertical sequence in which the data is stored is referred to as a column.  Each value in a spreadsheet is stored in a cell, which is the intersection of rows and columns.  A cell can contain either numeric value or a character string.

MS Excel System

        Worksheet is the actual working area consisting of rows and columns. The worksheets are also known as the spreadsheets. A work book in MS Excel is a combination of several worksheets. Each workbook of MS Excel contains three worksheets by default. The key operations that are performed in MS Excel include: Creating a worksheet Saving a worksheet Modifying a worksheet Renaming a worksheet Deleting a worksheet Moving a worksheet Editing a worksheet

MS PowerPoint System

 MS PowerPoint is a software application included in the MS Office package that allows us to create presentations. PowerPoint provides a GUI with the help of which we can create attractive presentations quickly and easily.  The presentation may include slides, handouts, notes, outlines, graphics and animations. A slide in PowerPoint is a combination of images, text, graphics, charts, etc. that is used to convey some meaning information.  The presentations in MS PowerPoint are usually saved with the extension .ppt. The interface of MS PowerPoint is similar to the other interfaces of MS Office applications.  PowerPoint presentations are commonly used in business, schools, colleges, training programs, etc.

MS PowerPoint System

 The following are the key operations that can be performed in MS PowerPoint:      Creating a new presentation Designing the presentation Saving a new presentation Adding slides to the presentation Printing the presentation

Data Communications and Networks

Introduction

    Computers were originally developed as standalone, single-user systems. Stand-alone computers can receive user issues were raised.

’ s data, manipulate them and provide useful information for making decisions. Here, the user uses his own data for his own decision making purposes. When the use of computers spread across government offices and business organizations, a number of What if a user wants to share his computer generated information with other colleagues?

What if a user want s to explore the possibility of using certain information stored else where?

Theses issues were addressed by the subsequent developments in software, hardware and communication technologies which have enabled the computers to communicate between each other and exchange information quickly and accurately and at any time.

Introduction

 The process of electronic transfer of information between two locations is known as data communication. The five basic elements of data communication are:      Message: It is the information to be communicated. It may be in the form of text, pictures, audio, video, or any combination of these.

Sender: It is the device that creates and transmits the information.

Receiver: It is the device that receives the information.

Medium: It is the communication channel through which the information travels from sender to receiver. It could be a physical wire or radio waves.

Protocol: It represents a set of rules that governs the communication process between the sender and the receiver.  Data communication may occur in a simple point-to-point mode or in a multipoint mode where more than two computers are connected together in the form of a network. A network is a system of interconnected computers that can communicate with one another to share applications and data.

Computer Network

 Computer network is a system of interconnected computers that enable the computers to communicate with each other and share their resources, data and application.  The physical location of each computer is tailored to personal and organizational needs. A network may include only personal computers or a mix of PCs, minis and mainframes spanning a particular geographical area.  Computer networks that are commonly used today may be classified as follows:

Computer Network

 Based on geographical area:      Local Area Networks (LANs) Wide Area Networks (WANs) Metropolitan Area Networks (MANs) International Network (Internet) Intranet

Computer Network

 Based on how computer nodes are used:    Client Server Networks (CSNs) Peer-to-Peer Networks (PPNs) Valued-added Networks (VANs)

Local Area Network (LAN)

   LAN is a group of computers that are connected in a small area such as building, home, etc. Through this type of network, users can easily communicate with each other by sending and receiving messages. Though the number of computers connected in a LAN is limited, the data is transferred at an extremely faster rate.

LAN



Wide Area Network (WAN)

WAN is a group of computers that are connected in a large area such as continent, country, etc. WAN is generally used for connecting two or more LANs through some medium such as leased telephone lines, microwaves, etc. In WAN, data is transferred at slow rate.

LAN LAN WAN LAN LAN

Metropolitan Area Network (MAN)

   MAN is a network of computers that covers a large area like a city. The size of the MAN generally lies between that of LAN and WAN, typically covering a distance of 5Km to 50 Km. The geographical area covered by MAN is comparatively larger than LAN but smaller than WAN. MAN is generally owned by private organizations. MAN is generally connected with the help of optical fibres, copper wires etc. One of the most common example of MAN is cable television network within a city. A network device known as router is used to connect the LANs together. The router directs the information packets to the desired destination.

LAN LAN Router Router Router LAN LAN LAN LAN Cable television network

The Internet

      The Internet is a global area network that allows computers connected over the network to share resources and information using different protocols. It is basically a network of networks across the globe. Users at different locations can very easily communicate with each other via the Internet. The Internet basically uses a set of protocols such as Transmission Control Protocol/Internet Protocol (TCP/IP) for transferring the data over the network. The following are the different types of services provided by the Internet to the users: E-mail Online chat Online shopping …

The Internet

 There are various advantages of using the Internet:    Information: The Internet allows users to access large amount of information efficiently. Availability: The Internet is available continuously to the users all the time without any delay. Users can access the information from the Internet at any time.

Cost: The Internet provides different facilities to the users at a low cost. Users can access any website over the Internet absolutely free. The cost of sending messages through e-mail is also cheaper as compared to postal messages.

The Internet

 The following are some of the disadvantages of using the Internet:    Hacking: The process of illegally accessing the personal information stored over the Internet is called hacking.

Virus: The software program that itself gets activated in our computer system and destroys the stored information is called virus. Virus usually corrupts the resources that are connected over the Internet.

Bulk e-mail: It is the most common problem of the Internet where the unwanted bulk messages such as subscription mails, advertisement mails, job alert mails etc. are received on the users account. These messages are sometimes frustrating and irritating for the users because the user simply does not require these mails.

The Intranet

    Intranet is a private network, which is confined at a single organization only. This type of computer network allows only the internal users of the organization to share the resources. However, the users outside the organization can also access the Intranet but they can do so only if they are authorized. The concept of Intranet was used for sharing the company TCP/IP, HTTP, etc. are used by Intranet for enabling the communication between the computer systems. ’ s information amongst the employees. Certain protocols such as The website of the Intranet is provided with the firewall, which is a layer that helps in ensuring the security of the information and resources. The only disadvantage of Intranet is that it is relatively insecure as compared to the other networks.

The Intranet

 The various advantages of using Intranet are as follows:    It allows the employees of an organization to access the organizations ’ information easily and quickly Intranet users can easily communicate with each other within the organization It is relatively easier to maintain and implement Intranet than the Internet

Client Server Network (CSN)

   CSN basically consists of two computers, client computer and server computer. The client computers are dummy computers, which simply send requests to the server computer, whereas the server computers receive and execute the requests sent by the client computer. CSN is also known as the client server architecture. This architecture is a two-tier architecture, which is divided into two layers. The first layer comprises of the user interface that is located on the client the clients.

’ s desktop. On the other hand, the second layer is the database management layer, which is located on the server machine so as to provide services to In CSN, a client computer sends a request related to processing of data to the server. The server receives the request from the client computer and processes the data. It then sends the output obtained after the processing of data to the client computer as a response to its request. Server Client Client Client

Peer-to-peer Network (PPN)

   In PPN, there is no separate division as clients and servers. Every computer in the PPN is treated equally and can send as well as receive the messages directly. PPN architecture cannot work under heavy load. This type of architecture is commonly used for file sharing and chatting in real time. Computers connected in this network can easily share their resources with the other computers. PPN is used in a variety of fields such as business, education, telecommunications, military etc.

Peer1 Peer2 Peer5 Peer3 Peer4

Network Topologies

 Network topology refers to the arrangement of computers connected in a network through some physical medium such as cable, optical fibre etc. Topology generally determines the shape of the network and the communication path between the various computers (nodes) of the network. The various types of network topologies are as follows:       Hierarchical topology Bus topology Star topology Ring topology Mesh topology Hybrid topology

Hierarchical Topology

    The hierarchical topology is also known as tree topology, which is divided into different levels. This type of topology is arranged in the form of a tree structure in which top level contains parent node (root node), which is connected with the child nodes in the second level of hierarchy with the point to-point link. The second level nodes are connected to the third level nodes, which in turn are connected to the fourth level nodes and so on.

Except the top-level node, each level node has a parent node. Top level Second level Third level

Linear Bus Topology

  In the linear bus topology, all the nodes are connected to the single backbone or bus with some medium. When a node wants to communicate with the other nodes in the network, it simply sends a message to the common bus. All the nodes in the network then receive the message but the nodes for which it was actually sent only processes it. The other nodes discard the message.

Cable end Cable end

Star Topology

   In the star topology, all the nodes are connected to a common device known as hub. When a node wants to send a message to the other nodes, it first sends the message to the hub, which in turn forwards the message to the intended node. Each node in the network is connected with a point-to-point line to the centralized hub. The task of hub is to detect the faulty node present in the network. On the other hand, it also manages the overall data transmission in the network.

Hub

Ring Topology

    In the ring topology, the nodes are connected in the form of a ring. Each node is connected directly to the other two nodes in the network. The node, which want s to send a message, first passes the message to its consecutive node in the network. Data is transmitted in the clock wise direction form one node to another. Each node incorporates a repeater, which passes the message to next node when the message is intended for another node.

Mesh Topology

   In mesh topology, each computer is connected to every other computer in point-to-point mode. For example, if we have four computers, we must have six links. If we have computers, we must have n ( n n -1)/2 links. A message can take several possible paths to reach a destination.

Hybrid Topology

   The hybrid topology is the combination of multiple topologies, used for constructing a single large topology. The hybrid topology is created when two different network topologies are interconnected. If two ring topologies are connected then the resultant topology is not the hybrid topology. On the other hand, if the ring topology is connected to the bus topology then the resulting topology is called the hybrid topology. This topology generally combines the features of the two topologies and is therefore more effective and efficient than the individual topologies.

Network Media

 Network media refers to the physical media used to connect the computer nodes together. There are many types of transmission media, the most popular ones are:  Cables: Some of the commonly used cables are telephone lines, twisted-pair cables, coaxial cables. Cable is one of the easiest methods of transferring messages from one place to another.

 Optical fibre: A thin strand of glass that transmits pulsating beams of light rather than electric current. These light pulses carry information. Fibre-optic cables can thus carry information in digital form. They can carry enormous amount of messages at extremely fast speed. These are used for long distance communications. It is a highly secured transmission medium.

Network Media

 Microwave: communication through microwave can be used when the transmitting and receiving ends are located at a large distance from one another. Microwaves are used to transmit analogy signals. WANs often use microwave links to connect LANs together. This mode of transmission is greatly affected by the weather conditions.  Satellite: Satellites are used for receiving and transmitting analog signals globally. We can send data from one country to another with the help of satellites. WANs that cover long distances often use satellites for linking LANs.

Network Protocol

    In order to share data between computers, it is essential to have appropriate network protocols and software. With the help of network protocol, computers can easily communicate with each other and can share data, resources etc.

Network protocols are the set of rules and regulations that are generally used for communication between two networks. Any two networks communicate with each other by sending and receiving messages in the form of packets. The techniques that is used separating a message into packets is called packet switching. Each packet contains the address of the computer from which the message was sent and also of the computer, which will receive the message. In order to send the packet, routers and switches are connected over the network path that forwards, the packet to the intended receiver.

Network Protocol

 Using network protocol, the following tasks can be performed:     Identification of the type of the physical connection used Error detection and correction of the improper message Initiation and termination of the communication session Message formatting  Some of the commonly used network protocols are Hyper Text Transfer protocol (HTTP), Simple Mail Transfer Protocol (SMTP), File Transfer Protocol (FTP), Transmission Control Protocol/Internet Protocol (TCP/IP), Telecommunications Network (Telnet), Domain Name System (DNS) etc.

Network Software

   Network software refers to the set of instructions that are given to the computers connected in a network to perform different tasks. These instructions are given in the form of a program, which is usually written in some programming language such as C++, Java, C etc.

The network software generally provides support to the computers connected in a network so that they can communicate with each other by exchanging information.

Network operating system software is the type of network software that basically controls the network traffic, access to the network resources such as printers, files, etc. This type of software generally provides multiuser, multitasking facilities so as to ensure effective communication between the computers over the network. It also establishes the communication between multiple computers that are performing a single task.

Applications of Network

 Network is the system of computers generally linked together to enable the flow of data between the interconnected computers. With the help of network, we can access the data remotely. Some of the applications of a network are:  Data sharing: In order to share the data among multiple users, it is generally stored on the servers. Different applications can therefore access the data from these servers easily.

 Remote data access: Remote data access is the process of accessing the data from remote location in an efficient way. Different software programs are used to provide an interface to the end users for accessing the data remotely.

Applications of Network

  Resource sharing: It is the process of sharing the resources such as storage devices, input/output devices, etc. over the network. For example, printer can be shared among the computers connected in a network by attaching it to the server computer. When the users want their documents to be printed they can simply give the print command from there computers and get their document printed. The sharing of a printer on a network is relatively cheaper than attaching separate printers to the individual computer connected in the network.

Personal communication: The far-reaching applications of networks are electronic mail and teleconferencing. These applications allow individuals as well as organizations to use networks for exchanging messages (written, voice and video) extensively. Emails enables a person to send and receive instant messages over a computer network with the help of Internet. On the other hand, teleconferencing enables real-time communication over a distance by allowing people at different locations to communicate with each other by seeing the video picture of people at other sites.

The Internet and World Wide Web

The Internet and World Wide Web

 Internet is a popular buzzword among many people today. Almost everyone working in government offices and business organizations is using the Internet for exchange of information in one form or the other.

 World Wide Web is another popular phrase among the computer users. It is commonly referred to as the Web. Most people consider the Internet and the World Wide Web to be synonymous, but they are not. Although these two terms are used interchangeably, they actually describe two different but related things.

The Internet and World Wide Web

  The Internet is a massive network of networks that links together thousands of independent networks thus bringing millions of computers on a single network to provide a global communication system. It acts as a facilitator for exchange of information between computers that are connected to the Internet. It is like a network of roads in a country that facilitates the movement of vehicles around the country.

We can create special documents known as hypertext documents containing text, graphics, sounds and video on a computer. The storage location of these documents is known as website. The World Wide Web is the network of all such websites all around the world. It is popularly known as WWW or Web. The websites are spread across the Internet and therefore, the information contained in the websites can be transmitted through the Internet. It is like transporting the goods stored in the warehouses using the road network. So the Web is just a portion on the Internet and not same as the Internet.

Understanding the World Wide Web

   WWW is a collection of web servers, which contain several web pages pertaining to different websites. The web pages contain hypertext, simple text, images, videos and graphics. The web pages are designed with the help of HyperText Markup Language (HTML). To view the web pages provided by a web server, the software known as web browser is required. To display the web pages, a web browser runs the HTML code segment written for a particular web page. Each web page on the Internet is provided its own address known as Uniform Resource Identifier (URI or URL). This URL helps the web browser in locating a web page on the Internet. A URL string begins with the name of a protocol such as http or ftp that represents the protocol through which a web page is accessed. The rest of the URL string contains the domain server name of the web page being accessed and the location of the web page on the local web server.

Web Browsers

 Web browser is the software, which is used to access the Internet and the WWW. It is basically used to access and view the web pages of the various websites available on the Internet. A web browser provides many advanced features that help achieve easy access to the Internet and WWW.  When we open a web browser, the first page, which appears in the web browser window, is the home page set of that particular web browser.

 The most commonly used web browsers are Internet Explorer (IE), Netscape Navigator and Mozilla Firefox.

Protocols Used for the Internet

 Each computer on a network has a unique address, which is known as the Internet Protocol (IP) address.  An IP address is a group of four numbers and the numbers are separated from each other by a dot. When any data is sent from one computer to another computer over the network, it is divided into small modules known as packets or datagrams. These packets are transmitted on the network by the Internet Protocol.  Each packet transmitted on the network contains the addresses of both source and destination computer. A gateway present on the network reads the address of the destination computer and sends the data to the specified address. Gateway is a computer, which contains the software required for the transmission of data over different networks.

Protocols Used for the Internet

    Each packet on the network is an independent entity, so they are transferred through different routes to reach the destination computer. The packets received at the destination are not in the same sequence in which they were transmitted. As a result, these packets are arranged in a right sequence by a protocol known as TCP and then are merged at the destination to form the complete data. TCP and IP work in coordination with other protocols such as Telnet and User Datagram Protocol (UDP) but are considered as the most fundamental of all protocols. All these protocols are collectively known as TCP/IP suite. A model known as TCP/IP model determines how the protocols of the TCP/IP suite will work together for the transfer of data between computers in a network.

TCP/IP Model

  The TCP/IP model was initially developed by US Defence Advanced Research Projects Agency (DARPA). This model is also known as the Internet Reference model or DoD model. It consists of four layers, namely application layer, transport layer, network layer, and physical layer.

The physical layer in the TCP/IP model is responsible for interacting with the medium of transmission of data, whereas the application layer helps in interacting with the users. The four layers of TCP/IP and the functions performed by the these layers are as follows: Application Layer Transport Layer Network Layer Physical Layer

TCP/IP Model

 Application layer: It is responsible for managing all the user interface requirements. Many of the protocols, such as telnet, FTP, SMTP, DNS, NFS, LPD, and DHCP work on this layers.

 Transport layer: It is responsible for the delivery of packets or datagrams. It also hides the packet routing details form the upper layer, i.e. the application layer. In addition, the transport layer allows detection and correction of errors and helps to achieve end-to-end communication between devices. The transport layer connects the application layer to the network layer through two protocols , namely TCP and UDP.

TCP/IP Model

    Network layer: It contains three protocols that perform different functions: Internet Protocol (IP): IP is a connectionless protocol that is responsible for the delivery of packets. The IP protocol contains all the address and control information for each transmitted packet.

Internet Control Message Protocol (ICMP): It is responsible for reporting errors, sending error messages and controlling the flow of packets. It is more reliable than the IP as it is capable of determining errors during data transmission Address Resolution Protocol (ARP): It is responsible for determining the Media Access Control (MAC) address corresponding to an IP address. It sends an ARP request on the network for a particular IP address and the device, which identifies the IP address as its own, returns and APR reply along with its MAC address.

TCP/IP Model

 Physical layer: It is responsible for collecting packets so that the frames, which are transmitted on the network, can be formed. It performs all the functions required to transmit the data on the network and determining the ways for accessing the medium through which data will be transmitted. This layer does not contain any protocols but instead of protocols, it contains some standards such as RS-232C, V.35 and IEEE 802.3.