8-Computer-Science-1to3.docx

**Introduction** Number system is a way to represent numbers or symbols in a systematic way. In digital systems, the information is represented using the symbols of the number system. The total number of symbols in a number system is called base or radix of the number system. In general, there are...

**Introduction** Number system is a way to represent numbers or symbols in a systematic way. In digital systems, the information is represented using the symbols of the number system. The total number of symbols in a number system is called base or radix of the number system. In general, there are two types of number systems. They are given below The most popular number systems of positional number system are explained below. **Types of Number Systems** The distinct symbols or numbers used in a number system is called base or radix of the number systems. It is represented as subscript to the number to identify the type of the number system as the same symbols or digits may be available in two or more number systems. The various number systems and its symbols are given below. S.No Number System Base/Radix Symbols used Example ------ --------------- ------------ ---------------------------------- ----------- 1. Binary 2 0 and 1 10010~2~ 2. Decimal 10 0,1,2,3,4,5,6,7,8,9 89104~10~ 3. Octal 8 0,1,2,3,4,5,6,7 17602~8~ 4. Hexa decimal 16 0,1,2,3,4,5,6,7,8,9, A,B,C,D,E,F 8A6D~16~ The binary number system plays an important role in the design of electronic circuits as the digital circuits can understand only binary digits 0 or 1. Let us discuss in detail about the binary number system. **Binary Number System** Binary number system uses only two digits such as 0 or 1 for representing any values or symbols. The digits 0 or 1 are called a bit (binary digit). Each digit in a binary number system is represented by the successive powers of 2. The positional values for each digit from right to left are weighted as 2^0^=1, 2^1^=2, 2^2^=4, 2^3^=8, 2^4^=16, 2^5^=32, 2^6^=64 etc. The four bit binary equivalents of the decimal number from 0 to 15 are given below. Decimal Binary Decimal Binary --------- -------- --------- -------- 0 0000 8 1000 1 0001 9 1001 2 0010 10 1010 3 0011 11 1011 4 0100 12 1100 5 0101 13 1101 6 0110 14 1110 7 0111 15 1111 A four bit binary number can represent the maximum of 16 values i.e. 2^4^=16 ranging from 0000 to 1111 (0 to 15). Similarly a 6 bit binary number can represent 2^6^=64 ranging from 000000 to 111111 (0 to 63). Can you guess the range of values for a 16 bit binary number? **Binary Arithmetic** Like a decimal number system, arithmetic operations such as addition, subtraction, multiplication and division can be performed using binary number system. Let us discuss four arithmetic operations such as addition, subtraction, multiplication and division in binary number system. The weighted values for the position of binary number system are as follows 2^5^ 2^4^ 2^3^ 2^2^ 2^1^ 2^0^ ------ ------ ------ ------ ------ ------ 32 16 8 4 2 1 **Binary Addition** The following table summarizes the rules for performing addition of two binary numbers A B A+B --- --- ----- 0 0 0 0 1 1 1 0 1 1 1 10 Let us see some of the examples for binary addition. Note that addition of digits should be performed from the right to left. +-----------------------------------+-----------------------------------+ | Add the binary numbers | Add the binary numbers | | | | | 1001~2~ + 1011~2~ | 101.101~2~ + 111.11~2~ | | | | | +--------------+--------------+ | +--------------+--------------+ | | | Carry\-\-\-- | 111 | | | Carry\-\-\-- | 111 | | | | \> | | | | \> | | | | +==============+==============+ | +==============+==============+ | | | First | 1001 | | | First | 101.101 | | | | number\-\-\- | | | | number\-\-\- | | | | | -\> | | | | -\> | | | | +--------------+--------------+ | +--------------+--------------+ | | | Second | 1011 | | | Second | 111.11 | | | | number-\> | | | | number-\> | | | | | | \-\-\-\-\-\- | | | | \-\-\-\-\-\- | | | | | \-\-\-\-- | | | | \-\-\-\-\-- | | | +--------------+--------------+ | +--------------+--------------+ | | | Result\-\-\- | 10100 | | | Result\-\-\- | 1101.011 | | | | \-\-\-\-\-\- | | | | \-\-\-\-\-\- | | | | | \-\--\> | \-\-\-\-\-\- | | | \-\--\> | \-\-\-\-\-\- | | | | | \-\-\-\-- | | | | \-\-\-\-\-- | | | +--------------+--------------+ | +--------------+--------------+ | | | | | 1001~2~ + 1011~2~ = 10100~2~ | 101.101~2~ + 111.11~2~ = | | | 1101.011~2~ | +===================================+===================================+ | Add the binary numbers 101101~2~ | Add the binary numbers | | + 101111~2~ | 11~2~+101~2~ | | | | | +--------------+--------------+ | +--------------+--------------+ | | | Carry\-\-\-- | 11111 | | | Carry\-\-\-- | 11 | | | | \> | | | | \> | | | | +==============+==============+ | +==============+==============+ | | | First | 101101 | | | First | 11 | | | | number\-\-\- | | | | number\-\-\- | | | | | -\> | | | | -\> | | | | +--------------+--------------+ | +--------------+--------------+ | | | Second | 101111 | | | Second | 101 | | | | number-\> | | | | number-\> | | | | | | \-\-\-\-\-\- | | | | \-\-\-\-\-\- | | | | | \-\-\-\-- | | | | \-- | | | +--------------+--------------+ | +--------------+--------------+ | | | Result\-\-\- | 1011100 | | | Result\-\-\- | 1000 | | | | \-\-\-\-\-\- | | | | \-\-\-\-\-\- | | | | | \-\--\> | \-\-\-\-\-\- | | | \-\--\> | \-\-\-\-\-\- | | | | | \-\-\-\-- | | | | \-- | | | +--------------+--------------+ | +--------------+--------------+ | | | | | 101101~2~ + 101111~2~ = | 11~2~+101~2~= 1000~2~ | | 1011100~2~ | | +-----------------------------------+-----------------------------------+ **Binary Subtraction** The following table summarizes the subtraction of any two binary digits. A B A-B --- --- ----- 0 0 0 1 1 0 1 0 1 0 1 1 (0-1= 1 only if borrow exists in the next higher column) Let us see some of the examples for binary subtraction. Note that subtraction of digits should be performed from the right to left. +-----------------------------------+-----------------------------------+ | Subtract binary numbers | Subtract two binary numbers | | | 101101~2~ - 1111~2~ | | 110~2~-101~2~ | | | | First number\-\-\--\> 10 | | +--------------+--------------+ | 1101 | | | First | 110 | | ---------------------------- -- | | | number\-\-\- | | | ------------------- | | | -\> | | | Second number-\> 11 | | +==============+==============+ | 11 | | | Second | 101 | | \- | | | number-\> | | | \-\-\-\-\-\-\-\-- | | | | \-\-\-\-\-\- | | Result\-\-\-\-\-\-\-\-\--🡪 11 | | | | \-- | | 110 | | +--------------+--------------+ | \- | | | Result\-\-\- | 001 | | \-\-\-\-\-\-\-\-- | | | \-\-\-\-\-\- | | | | | | \-\--\> | \-\-\-\-\-\- | | 101101~2~- 1111~2~ = 11110~2~ | | | | \-- | | | | +--------------+--------------+ | | | | | | 110~2~-101~2~= 001~2~ | | +===================================+===================================+ | Subtract binary numbers | Subtract binary numbers | | | | | 110.01~2~-101.11~2~ | 11110~2~-11101~2~ | | | | | +--------------+--------------+ | +--------------+--------------+ | | | First | 110.01 | | | First | 11110 | | | | number\-\-\- | | | | number\-\-\- | | | | | -\> | | | | -\> | | | | +==============+==============+ | +==============+==============+ | | | Second | 101.11 | | | Second | 11101 | | | | number-\> | | | | number-\> | | | | | | \-\-\-\-\-\- | | | | \-\-\-\-\-\- | | | | | \-\-\-\-- | | | | \-\-\-\-- | | | +--------------+--------------+ | +--------------+--------------+ | | | Result\-\-\- | \-\-\-\-\-\- | | | Result\-\-\- | 00001 | | | | \-\-\-\-\-\- | \-\-\-\-- | | | \-\-\-\-\-\- | | | | | \-\--\> | | | | \-\--\> | \-\-\-\-\-\- | | | +--------------+--------------+ | | | \-\-\-\-- | | | | +--------------+--------------+ | | 110.01~2~-101.11~2~= 000.10~2~ | | | | 11110~2~-11101~2~= 00001~2~ | +-----------------------------------+-----------------------------------+ Note: To verify the result, add the result and the second number to get the first number. **Memory Units** The data can be stored in the memory devices using a bit format such as 0 or 1. So the data gets internally converted to 0 or 1 for storage. The sequence of bits in binary number system can be defined as boundaries. They are as follows Unit name Description Example ---------------- ------------- --------- Bit 1 bit Nibble 4 bits Byte 8 bits Word 16 bits Double word 32 bits Kilo Byte (KB) 1024 bytes Mega Byte(MB) 1024 KB Giga Byte (GB) 1024 MB Tera Byte (TB) 1024 GB Peta Byte (PB) 1024 TB **NUMBER SYSTEM CONVERSIONS** Computer can handle any symbol or number in the form of binary digits only. So it is necessary to know the procedure for converting numbers from one system to other. Let us discuss in detail about various types of conversions. **Decimal to Other Number System** The following steps summarize the method of converting a decimal number to other systems such as binary, octal and hexadecimal. 1. 2. 3. 4. **Decimal to Binary** A decimal number is converted to binary number using the above steps and the base value is 2. Example: Convert a decimal number 634~10~ into binary number. 2 634 --- ----- --- 2 317 0 2 158 1 2 79 0 2 39 1 2 19 1 2 9 1 2 4 1 2 2 0 2 1 0 0 1 Now the quotient is 0, so stop the division and write the equivalent binary number of the given decimal number from bottom to top i.e. 634~10~ = 1001111010~2~ **Binary to Decimal** We multiply each digit by its weighted position, and add each of the weighted values together to get the equivalent decimal number. The simple formula for this operation is as follows. 1. 2. 3. Example: +-----------------------------------------------------------------------+ | ### Convert the binary number 10111~2~ into decimal number | | | | ### | | | | ### = 1 X 2^4^ + 0 X 2^3^ + 1 X 2^2^ + 1 X 2^1^ + 1 X 2^0^ | | | | = 1 X 16 + 0 X 8 + 1 X 4 + 1 X 2 + 1 X 1 | | | | = 16 + 0 + 4 + 2 + 1 | | | | = 23~10~ | +=======================================================================+ | | +-----------------------------------------------------------------------+ **Octal Number System** The base of the octal number system is 8 and the symbols are 0 through 7. Three binary bits are grouped to represent a digit in octal number. Converting binary to octal and vice versa is very easy. The binary equivalent of octal number is as follows. Octal 0 1 2 3 4 5 6 7 -------- ----- ----- ----- ----- ----- ----- ----- ----- Binary 000 001 010 011 100 101 110 111 **Hexadecimal Number System** The hexadecimal (base 16) number system is a positional number system. The hexadecimal number system uses not only the Arabic numerals 0 through 9, but also uses the letters A, B, C, D, E, and F to represent the equivalent of 10~10~ through 15~10~, respectively. The same principles of positional number systems we applied to the decimal, binary, and octal number systems can be applied to the hexadecimal number system. However, the base of the hexadecimal number system is 16, so each position of the hexadecimal number represents a successive power of 16. From right to left, the successive positions of the hexadecimal number are weighted 1, 16, 256, 4096, 65536, etc.: The following table gives the binary equivalent of the hexadecimal and other number systems Decimal Octal Binary Equivalent for octal Hexadecimal Binary equivalent of Hexadecimal --------- ------- ----------------------------- ------------- ---------------------------------- 0 0 000 0 0000 1 1 001 1 0001 2 2 010 2 0010 3 3 011 3 0011 4 4 100 4 0100 5 5 101 5 0101 6 6 110 6 0110 7 7 111 7 0111 8 10 001 000 8 1000 9 11 001 001 9 1001 10 12 001 010 A 1010 11 13 001 011 B 1011 12 14 001 100 C 1100 13 15 001 101 D 1101 14 16 001 110 E 1110 15 17 001 111 F 1111 **Computer Codes** The process of converting data into an equivalent cipher using specific code is called encoding. All the characters, symbols, letters are represented using the special codes like BCD, ASCII, ISCII, Unicode etc. **BCD code** The term BCD stands for Binary Coded Decimal, in which each decimal digit is represented by the four bit binary equivalent. If the decimal number consists of more than one digit, then each digit will be replaced by the 4-bit binary number. It is widely used in many electronic devices such as calculators, digital clocks, digital voltmeters, electronic counters etc. **ASCII Character code** Humans understand languages but computer knows only binary numbers, so a system is required for representing the symbols. ASCII is one among the system for representing the symbols in the computer. The full form of ASCII is American Standard code for information interchange (Pronounced as ask-ee). It is one of the most popular computer code, widely used in all over the world by several manufacturers of computer and software. ASCII is the standard coding pattern for the characters, which is mainly used for exchange of information between the computers. It is also used in many computer languages, software and for data communication between computers. **ISCII Code** It stands for Indian Standard code for information interchange. The main purpose of ISCII is to facilitate the use of Indian languages on computers. It is an 8-bit code representation for Indian languages which means it can represent 28=256 characters. It retains all 128 ASCII codes and uses rest of the codes (128) for additional Indian language character set. **Unicode** It has been developed to incorporate all the characters of every written language of the world. UNICODE provides a unique number for every character, irrespective of device (server, desktop, mobile), operating system (Linux, Windows, iOS) or software application. Unicode uses two encoding forms: 8-bit, 16-bit and 32 bit, based on the data type of the data that is being encoded. The default encoding form is 16-bit, where each character is 16 bits (2 bytes) wide. **EXERCISE** **A. Fill in the blanks** 1. The radix or base of the octal number system is \_\_\_\_\_\_\_. 2. A byte consists of \_\_\_\_\_\_\_ bits. 3. The binary equivalent of 89~10~ is \_\_\_\_\_\_\_. 4. In binary, the result of 1~2~+1~2~ = \_\_\_\_\_\_\_. 5. The decimal equivalent of the binary number 1011011~2~ is \_\_\_\_\_\_\_. **B. State true or false** 1. The decimal number system is used for internal representation of data in the computer. 2. The base of the hexadecimal number system is 16. 3. A word consists of 8 bits. 4. In binary subtraction, the result of 1-0 is 0 5. The binary digits 0 and 1 are used to represent OFF and ON status of electronic circuits respectively. **C. Give short answer for the following** 1. Explain binary and octal types of number systems. 2. What is the significance of binary number system? 3. Define: BIT, NIBBLE, BYTE and WORD. 4. Perform the following binary arithmetic. 5. Convert the following decimal numbers into binary. 6. Convert the following binary numbers into decimal. **2. Advanced HTML** **Introduction** HTML stands for **H**yper **T**ext **M**arkup **L**anguage. The term hypertext is the content of a document that includes text, pictures and it links to other related documents. It helps to create web pages and other information that can be displayed in a web browser. HTML provides several facilities to create an attractive webpage and to link related documents to navigate with in the document easily. WWW is nothing but a set of linked documents in hypertext form. Basically HTML document is a plain text file that contains text and the tags. It can be created with simple text editors (Notepad is widely used). When a browser opens an HTML file, the browser will look for HTML codes in the text and use them to change the layout, insert images, or create links to other pages. **Revision of HTML Tags** HTML contains rich set of tags for various purposes. Let us see some of the tags which were discussed in the previous classes. +-----------------+-----------------+-----------------+-----------------+ | S.No. | Tag name | Purpose | Example | +=================+=================+=================+=================+ | 1. | **\** | To create bold | \html is a | | | | text | markup | | | | | language\ | +-----------------+-----------------+-----------------+-----------------+ | 2. | **\** | To create | \ | | | | alignments | HTML is simple | | | | | to learn and | | | | | easy to score | | | | | mark \ | +-----------------+-----------------+-----------------+-----------------+ | 3. | **\** | To create a | P.Narasimman\Anuvikas | | | | | colony\Tar | | | | | apur\Mahar | | | | | ashtra | +-----------------+-----------------+-----------------+-----------------+ | 4. | **\** | It stands for | \ | | | | Preformatted | | | | | text. It | P.Narasimman | | | | displays the | | | | | text in a fixed | Anuvikas | | | | width font by | colony, | | | | preserving the | | | | | spaces and line | Tarapur, | | | | breaks | | | | | | Maharashtra, | | | | | Pin-401504 | | | | | | | | | | \ | +-----------------+-----------------+-----------------+-----------------+ | 5. | **\** | To create | \computer | | | | italics style | science\ | +-----------------+-----------------+-----------------+-----------------+ | 6. | **\** | Under line the | \TEST\ | | | | text | | +-----------------+-----------------+-----------------+-----------------+ | 7. | **\** | To center the | \CS | | | | text in browser | TEST | | | | area | \ | +-----------------+-----------------+-----------------+-----------------+ | 8. | **\** | intended as | was developed | | | | explanation or | by mlpn \--\> | | | | additional | | | | | information. | | +-----------------+-----------------+-----------------+-----------------+ | 9. | **\** | To create | H\2\So\4\ | +-----------------+-----------------+-----------------+-----------------+ | 10. | **\** | To create | Ax\2\ | +-----------------+-----------------+-----------------+-----------------+ | 11. | ** ** | To create blank | Hi    | | | | spaces | Nethu | +-----------------+-----------------+-----------------+-----------------+ **\** It is used to scroll the text across the screen in a horizontal or vertical direction. The area of the scrolling depends upon the container in which it is given. It can be created using the tags \ and \. Some of the attributes of this tag are as follows **BGCOLOR:** It specifies the background color for the marquee area. **DIRECTION:** It gives the direction to which the text should scroll. The default direction is towards left. The values are LEFT, RIGHT, UP and DOWN **BEHAVIOUR:** It specifies the type of scrolling, ie. The value ALTERNATE enables the scrolling from left to right and right to left. **WIDTH:** It gives the width of the browser area to be used for scrolling the text. Default width is 100%. **HEIGHT:** It specifies the height of the MARQUEE area for scrolling the text. **LOOP:** It specifies the browser how many times to move the marquee text across the screen **SCROLLDELAY:** defines the speed of the scrolling. (increase in the number makes slow in scrolling) Example 1: ------------------------------------------------------------------------------------------------------------------------------------------- *\WELCOME TO LEARNING TAGS OF HTML \* ------------------------------------------------------------------------------------------------------------------------------------------- The output of the tag will be as follows Example 2: ----------------------------------------------------------------------------------------------- *\The direction of text will be from bottom to top.\* ----------------------------------------------------------------------------------------------- **Hyperlinks** Hyperlink or HTML link is an HTML element that helps to create a link between documents. Hypertext is a text with hyperlinks which links text or an image with another HTML document. Hyperlinks can be created using \ tag i.e., Anchor tag. Linking can be within the same or different document or to the different websites. The command format is \ Link text / Image \ The href (hyper reference) attribute is used to specify the HTML file, URL or any document for the hyperlink. Example: 1. 2. **TABLES** Table helps to organize the data in a systematic manner. A table in html is nothing but the set of rows and columns like grids. The information presented in tables is much easier to read and understand. The basic structure of table consists of the following tags. \ and \ marks the beginning and end of the table. Some of the attributes associated with TABLE tag is as follows BGCOLOR: It specifies the thickness of the background colour of the table. BORDER: It specifies the thickness of the border of the table. If BORDER is equal to 0 then no border appears. **Tags used for creating rows and columns:** \ and \ - It is used to create a row in a table \ and \ - It stands for Table Header, this can be used mostly for the first row of the table data, it displays data as bold and center in the cell. \ and \ - It is used to create a cell data in a row of the table. COLSPAN: It helps to combine two or more cells of a column as a single column. ROWSPAN: It helps to combine two or more cells of a row as a single row. *We can also use bgcolor and Align attributes along with TH and TD tags to set the background color and to align the data.* **Example:** Create an HTML table to display the contact details of AEES with four columns Viz. Name, Organization/School, Designation and E-Mail address for three officers. \ \ \Contact Details of AEES\ \ \ \ \ \Name\ \Organization/School\ \Designation\ \Email address\ \ \ \Dr.V.P.Venugopalan\ \AEES\ \Chairman \ \chairman-aees\@nic.in\ \ \ \Shri.P.Goverdhan\ \AEES\ \Secretary\ \secretary\@aees.gov.in\ \ \ \Shri.Dileep Singh\ \AEES\ \Head Academic Unit\ \hau\@aees.gov.in\ \ \ \ \ The output of the above HTML code is as follows **LIST** Lists help us to organize data in a structured manner. Data can be displayed as list in a particular format using list tag. It is similar to bullets and numbering formats of word processing packages. We can create three types of lists in HTML as follows **Ordered List** It creates the list of items with the predefined numbering formats. The tags used for this purpose is as follows \ and \ - To open and close the list of items \ - It stands for LIST item, each item is preceded by \ tag and \ is an optional. TYPE -- It specifies the type of the number item to be included. Eg. TYPE ="1" to create numbers 1,2,3... TYPE ="A" to create numbers A,B,C... TYPE ="I" to create numbers I,II,III,IV... TYPE ="i" to create numbers i,ii,iii,iv... START specifies the starting value for the first item. Eg.\ Example: Write an HTML code to create the following list. **Vegetables** 1. 2. 3. 4. 5. **HTML Code** **Output** **Unordered List** The list of items can be preceded with the standard symbols like disk, square or circle using the tags of unordered list. The tags used for this purpose is as follows \ and \ - To open and close the list of items \ - It stands for List Item, each item is given preceded by \ tag. TYPE -- It specifies the type of the number item to be included.  Eg. TYPE ="circle" to create circle symbol TYPE ="disc" to create disc symbol TYPE ="square" to create square symbol Eg.\ **Example:** Create an HTML code to display the list of houses using unordered list. **Definition List** It is used to define the terms with a short description like the glossary of items available at the end of the books. The tags used for this purpose is as follows \ and \ to open and close the definition list. \ it is used for the title. \ Data Definition defines the description of the term given in DT. **EXERCISE** **A. Multiple Choice Questions** 1. The full form of HTML is 2. The syntax for including comments/remarks in HTML is 3. What is the correct way in which we can start an ordered list with number 5?. 4. In HTML, how do we insert an image? 5. How to create a hyperlink in HTML? 6. Which HTML tag do we use to display text along with a scrolling effect? 7. The command to create a blank space? a. 8. Which of the following attributes creates space between cells? **B. Answer the following** 1. What is use of \ tag? 2. How will you create superscript and subscript? 3. Name any 3 attributes of \ tag with its purpose. 4. How will you change the size and style of font? 5. Define the following attributes of \ tag. a. 6. What do you mean by hyperlink? Write the syntax for creating hyperlink. 7. Write the tags associated with creating rows and data in Table. 8. Write about the values to be used with attributes of \ tag. **C. Write the HTML code for the following problems** 1. Create a table to display time table for 5 days and 5 periods daily as follows. Day I-Period II-Period III-Period IV-Period V-Period ----------- ----------- ----------- ------------ ----------- ----------- Monday Maths Soc. Sci. Science Maths English Tuesday Science Maths English Hindi Soc. Sci. Wednesday Soc. Sci. English Hindi Science Maths Thursday English Science Hindi Soc. Sci. English Friday Hindi Maths Science English Soc. Sci. 2. Create a list for the following output. 1. a. b. c. 2. 1. 2. **D. Project Work** Create a webpage for any one of the following using all the necessary tags of HTML with images and tables. d. e. f. Introduction A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels. It facilitates communication and resource-sharing among a wide range of users by a standard protocol. It is an interconnected collection of autonomous computers that shares the resources. A network may contain two or more computers and other devices such as printers, scanner etc.  **Advantages of computer network** - - - - - - Components of network A network consists of various resources like hardware and software. The hardware components may include server, node, NIC, Modem, Switch/Hub etc. Let us discuss these components briefly. ========================================================================================================================================================================================== Server ====== A server is the main computer in the networking system. It is simply a computer with higher configuration that delivers information and software to other computers that are linked to it by a network either through cables or wirelessly through a router. It holds the control of all the resources and software that are to be shared among all the users of the network. undefined Server Requirements - - - - - - Servers are classified as dedicated server and non-dedicated server based on the way how it is being used in the network environment. Node or Clients =============== Any system or device connected to a network is called as node or client. For example, if a network connects a file server, five computers, and two printers, there are eight nodes on the network. Each device on the network has a network address which uniquely identifies each device.  Network Interface Card (NIC) ============================ A network is made up of various components. A Network Interface Card (NIC), is also known as an Ethernet card or Network Adapter. It allows connecting a computer with other devices such as Laptop, Server, Mobile, Desktop etc. via Ethernet cable. It is essential in network setup to allow the resources to communicate and share the information. ======================================================================================================================================================================================================================================================================================================================================================= **Connectors**  A connector is a device that helps to connect various components like hub, switch and server with a computer through guided media (cables). **Switch/Hub** A switch or hub is used to as a networking device to connect various devices into a network. A hub is a networking device that allows various computers/PCs and other devices to connect to a single network. A hub has many ports, and a computer that wants to connect to the network plugs into one of them.  A switch is a networking device that connects multiple devices on a single computer network but it is more intelligent than hub. **Cables** These are simply called as wire and it is used to connect various devices in a network. These cables are used to transfer data between the devices. Cables are classified into various categories depending upon their physical structure and it uses. Some of the types are coaxial cables, twisted pairs, fiber optical fibers, patch cables, data cables etc.  Other Resources =============== A networking system contains various resources like printer, disks, scanner, memory etc for the access by the programs. These devices can be shared for the group of computers connected in the network for effective utilization. Types of network Computer networks are classified into several categories depending upon the communication requirements, geographical area and the hardware used in the network. The major types of network is given below  Personal Area Network (PAN) =========================== net2.jpg A PAN network interconnects various devices within the short range of around 10 meters for a personal use. It is typically used for home or small office. It can transfer data through wireless or wired medium. Some of the devices that can be used in PAN are laptops, smart phones, tablets, wearables, printers and entertainment devices etc. LAN === A LAN is a Local Area Network, interconnecting large number of computers and other resources in a limited geographical area say within 1 km. Normally LANs are implemented in a single building or in a campus of an organization. It is generally used in colleges, Schools, research organizations, offices etc. In LAN system, nodes are connected to server via cables. **MAN** A MAN is a Metropolitan Area Network that connects different LANs in a particular city or town. It covers about few hundred kilometers which is smaller than WAN. These type of networks are used in telephone companies, cable TV, internet providers or organizations with offices in multiple locations. **WAN** A WAN is a Wide Area Network meant for digital communication system which interconnects different sites, computer installations and user terminals. It may also enable LANs to communicate with each other. A WAN is also known as Long Area Network. It may cover the whole country or the world. Internet is an example for WAN.  **Difference between LAN & WAN** S.No LAN WAN ------ ----------------------------------------------------------------------- ----------------------------------------------------------------------------- 1. Interconnection within small area like building Interconnection of LAN & MAN i.e. Country or world. 2. Data transfer rate is high. Data transfer rate is slow 3. Generally co-axial cables or fibre optic are used to connect the LAN. Links are provided using telephone lines or microwave towers or satellites. 4. Minimum errors in data transmission Due to long distance and short circuit errors, noise errors are higher. 5. Star or Ring topology can be provoked. Hybrid topology is used 6. Cost is less. Cost is high. 7. Number of nodes are limited Many nodes can be connected 8. It follows digital network It uses both digital and analog signal **Internet** Interconnection of networks is called as internet ie., network of networks. The term internet (small 'i') refers to large network made up of small network and Internet (capital 'I') refers global network. Global Internet comprises of millions of web pages, e-mails, servers etc. Internet was originally developed for U.S military and then later it was extended for educational and research purpose and finally the network was extended for the whole world. **Network topology** It is an arrangement of computers, server and various components of a network in a particular order; here the arrangement refers to physical and logical arrangement of devices. It is a layout of networks in which the admin can easily locate the nodes and helps for data transmission. Some of the network topologies are given below. **BUS Topology** It is a simple topology in which all the computers and other devices in the network are connected along a single cable that runs from one end to other. The drawback of this topology is it uses only one cable for data transmission and if the cable breaks, the whole network cannot function. **STAR Topology** In this layout, all the nodes are connected to a central server in star pattern. Each and every node is directly connected to the switch/hub and then to the server. All cables run to a central connection point. If one cable breaks or fails, only the computer that is connected to that cable is unable to use the network. This is the most widely used topology in LAN type of computer network. **Ring Topology** A ring topology connects the nodes in a circular path in which each computer will have direct connection with two computers. The data flows in a circular path, if first computer wants to send data to 5^th^ computer in a ring topology, then it has to cross 2 through 4 to reach 5.  The major disadvantage of a ring topology is that if any individual connection in the ring is broken, the entire network is affected. **Hybrid Topology** It is a combination of one or more topologies such as bus, ring, star etc. It is very effective and flexible. Network can be altered by adding or removing the nodes easily. The main drawback of this topology is that it is expensive and the design is difficult. **Network operating systems** A Network Operating System (NOS) is an operating system meant for the workstations or networks in which multiple nodes, server and other devices are connected through guided or wireless media. It manages data of various computers or servers in a secured manner and shares it with the permitted users. It helps to share various resources and files. Some of the Network Operating Systems are as follows ### Microsoft Windows Server: It is the most common NOS available in market. It is extremely powerful and takes care of every aspect of network. The latest version is Windows Server 2022. **UNIX Operating System:** was first developed by **AT&T Corporation's Bell Laboratories** in the late 1960s. The UNIX operating system is simple, multi-tasking, multi-user, portable and stable that is used for web servers, laptops, and desktop computers. **LINUX Operating System:** Linux is one of the most popular and open source operating system that is used in mobile phones, routers, super computers, mainframe computers, and server applications. The** **Linux Operating System is free and its source code is available to use. **Novell NetWare:** It was a powerful network operating system that offers essential features like user management, file sharing, and data security. It was discontinued and not available in the market. **EXERCISE** **A. Multiple Choice Questions** 1. Which of the following is not a feature of network? a\. shares resources b. exchange of information c\. requires no operating system d. reduces the cost 2. Full form of NIC in network is 3. Which of the following device is used for connecting computers to a network? 4. \_\_\_\_\_\_\_type of network is used to cover the entire world. 5. Which of the following refers to global network? 6. Which of these is a combination of one or more topologies? **B. Give very short answer for the following** 1. What do you mean by network? 2. Name any four components required for creating a network? 3. What is a node? 4. What is the purpose of connectors? 5. Which cable is fastest? 6. What do you mean by network topology? 7. Differentiate LAN and WAN. **C. Answer the following** 1. Explain the types of computer networks. 2. How will you differentiate Intranet and Extranet? 3. What are the various operating systems available for networking? 4. Explain networking with a diagram. 5. Explain different topologies with suitable diagrams.