Reviewer Intro to Computers PDF

**Computers**- play a significant role in handling all of the world\'s money. Below are examples of how computers are used in the financial market and places dealing with money. **ATM** - When **you make a withdraw** from an ATMLinks to an external site., you are using a computer. **Digital curre...

**Computers**- play a significant role in handling all of the world\'s money. Below are examples of how computers are used in the financial market and places dealing with money. **ATM** - When **you make a withdraw** from an ATMLinks to an external site., you are using a computer. **Digital currency**- When depositing money in a bank, it is stored as a digital record. A computer keeps track of how much money is in your account. **Trading** - **Stocks and commodities are traded using computers**. In fact, today there are even thousands of computers using advanced algorithmsLinks to an external site. that handle trading without needing humans. **Business**- is another big sector for computers and most money earned and spent is done using a computer. Below are some of the examples of how computers are used in business. - **Register** - If the business deals with selling goods to a consumer (e.g., a grocery store), a cash register, which is a computer, is used to complete transactions. - **Workers computer**- Many businesses assign each employee a computer that allows them to produce work and solve problems for the company. - **Server**- If the business uses computers, connects to the Internet, or handles e-mail and files, a serverLinks to an external site. is used to help manage everything. **communication around the world** is almost all digital and handled by computers. Below are examples of how computers are used in the communication industry. **Smartphone** - If you have a smartphoneLinks to an external site., you have a computer in your pocket. E-mail- More electronic mail (e-mailLinks to an external site.) is sent today than postal mail (snail mailLinks to an external site.), and computers handle all creation and distribution of that e-mail. **VoIP** - All voice over IP communication (VoIPLinks to an external site.) is handled and done by computers. Computer-assisted speech- Those who are disabled or cannot speak can use a computer to help them communicate. For example, Stephen HawkingLinks to an external site. uses a computer to communicated. Voice recognition - Any phone or another system that uses voice recognition Links to an external site.is using a computer to translate what is heard into text or other data that can be understood by the computer. Many technologies (e.g., GPS and the Internet) were initially created or started with a defense-related purpose. Today, computers are still an important aspect of the defense industry. Encryption - Secure communication is **vital in the defense industry and computers are used to encrypt Links to an external site.communications that should remain secret.** **GPS** - Using computers with GPSLinks to an external site.allows the military to track people and equipment and is still used today. **Computer-aided flight** - Many of today\'s jets and other aircraft require computers to fly and operate. **Drones** - A drone is either autonomous or remotely driven and uses computers to operate. Education As computers evolve, so does how computers are used in the education field. Below is a list of how a computer can be used in education. Internet - Connecting a student to the Internet gives him or her access to an endless supply of knowledge. As mentioned later, the Internet would not be possible without computers. Learning- Computers can also be used to help design and create a more visual learning experience for students. Using electronic whiteboardsLinks to an external site. with computers can also benefit a student by giving them a more hands-on experience. **Writing**- Although reports can still be done using pen, pencil, or even a typewriter, a computer makes it much easier to write, format, save, share, and print reports. **Keep records**- Computers are used to track students scores, identify struggling students, and are used to create a final report. **Testing-** Computers can assist students and teachers with the testing process by stepping the student through a series of questions and keep track of the results. Without computers, the InternetLinks to an external site. would not exist. Below are a few examples of computers are used to help run the Internet. **DNS-** When you type in a URLLinks to an external site. like https://www.computerhope.com/, a DNSLinks to an external site. must translate it into an IP addressLinks to an external site., which helps your computer to communicate with the server. **Web server**- Every web page requires a web serverLinks to an external site. or computer capable of receiving and sending requests when someone wants to view a web page. **Programs-** A computer is also needed to run scriptsLinks to an external site. and programsLinks to an external site.. For example, a search engineLinks to an external site., shopping cartLinks to an external site., or forumLinks to an external site. are all examples of programs that need a computer. **Services-** Other services like e-mail, FTPLinks to an external site., and SSHLinks to an external site. also require a computer or are daemonsLinks to an external site. on the web server. The medical field is another place where computers are vital and used every day. Below are some examples of how computers help those in the medical field. Medical records- More and more medical records are being digitally stored. Storing these files digitally allow for quick access and transfer of medical information so doctors can know your history. **Monitoring**- Computers help with monitoring a patient and can alert staff in the case of an emergency. Research- A lot of the medical research that is done today is computer assisted. Without the assistance of a computer, it would either not be possible or take so much longer that it wouldn\'t be viable. Diagnosis- Computers can assist in the diagnosis of a patient, from gathering a patient\'s history and conditions to comparing that information against a database of existing information. Surgery- Although most surgery is still done with humans, it is becoming more practical and accessible for computer robot-assisted surgery. After being programmed, these robots can make surgery more accurate, faster, and less prone to human errors. Transportation Computers also play an important part in transportation. Below are a few examples of how computers help the transportation field. **Cars-** Most may not realize it, but all modern cars today have multiple computers that help control and manage the vehicle. **Traffic lights**- The traffic lights that help control traffic are all run by computers. **GPS-** Cars that include a GPSLinks to an external site. mapping system have computers for display and calculating routes. **Airplanes-** The airplanes that help transport millions of people and goods every year are filled with computers that help control the plane. **Public transportatio**n- Train, bus, subway, and all forms of public transportation are highly dependent on computers to manage traffic flow, monitor operation, and handle payments. **Self-driving cars-** Although relatively new, self-driving cars are becoming increasingly popular and rely on a computer to make all decisions on how to drive. Multimedia Computers also play a significant role in video and audio. Below are examples of how computers are used in the film and audio industry. **Editing**- Once a movie, video, song, or audio track is created a computer can edit that media instead of having to manually make cuts to the film or audio track. **CGI-** Computer animationLinks to an external site. and CGILinks to an external site. has become a norm in big budget films. To create these effects computers and sometimes server farmsLinks to an external site. are used. **Manipulation**- Computers can be used to manipulate pictures, video, and audio. For example, someone could use Adobe PhotoshopLinks to an external site. to add or remove elements from an image. **Recording and playback**- Computers can also be used to assist in the recording of audio tracks and then selectively playback each audio track. **Creation-** Computers can also be used to help in creating new multimedia content. For example, creating 3D animation, 3D model, or a techno audio track can be done on a computer. After creating a 3D model, a 3D printerLinks to an external site. could also be used to build a product. **TV, DVD, media players-** Today\'s Smart TVsLinks to an external site., DVDLinks to an external site. players, DVRsLinks to an external site., etc., contain simple computing circuitry to connect the device to the Internet, run apps, and more. Robotics The industry of roboticsLinks to an external site. is exploding and computers once again play an important role in controlling robots. Below are some examples of how computers help control robotic machinery. **Control-** Computers are what help control robotics. For example, without a computer, an assembly robotic arm would not know where to place a part, what speed to operate, or if a problem has occurred. **Learning-** Computers can take the input given by a robot and take that information to help learn and adapt to new conditions. Simulations Some problems are so complex that it would be impossible for humans to calculate or would take too long to calculate. Computers are used to help solve these complex problems in a timely fashion. **Weather prediction**- Earth has an extremely complex weather system, and computers are used to gather all of the variables and create weather reports. **Product simulations-** Before some products go into development, computers simulate how they would work in the real world. By creating a simulation, a company or government agency can make adjustments before the product goes into development. **Big data simulation**- With cheap data storageLinks to an external site. companies can now store a massive amount of data. With this big dataLinks to an external site., a computer can be used to fjust ind unknown patterns. **A computer-** is an electronic device that accepts data from the user, processes it, produces results, displays them to the users, and stores the results for future usage. **Data-** is a collection of unorganized facts & figures and does not provide any further information regarding patterns, context, etc. Hence data means \"unstructured facts and figures\". **Information-** is a structured data i.e. organized meaningful and processed data. To process the data and convert into information, a computer is used. Characteristics of a Computer It is a machine. The computer needs human intervention to operate. It is electronic. The computer is made up of electronic components and is run by electricity. It is automatic. The computer can perform a set of instructions uninterruptedly once instructed. It can manipulate data. The computer can come up with an output given an input data. It has memory. The computer can store and retrieve information. It has logical functions. The computer is capable of performing not only mathematical operations but logical operations as well. Capabilities of a Computer 1\. Speed Computers can process data at a very high speed. 2\. Accuracy Computers process the data prepared by the users. That is, if the input is wrong, the output will be wrong also. 3\. Repetitiveness Computers can work continuously and repetitively. 4\. Storage Computers can store and retrieve relatively large amount of data. 5\. Programmable Computers can take a series of instructions and automatically execute each instructions one after another. Classifications of Computer A. According to Purpose **General** -- Purpose Computers. Capable of dealing with a variety of **Special** -- Purpose Computers. Designed to perform a specific task, with limited capabilities, and the program of instructions is build into the machine. B. According to Data Handled **Analog Computers-** Deal with continuously changing physical data Such as pressure, temperature ( or data that can be measure ). They are used for scientific, engineering and process -- control purposes -- operations which result to approximated values. **Digital Computers-** Work with values that are in a discrete from (or Data that can be counted). They are use for business applications, and also scientific operations, and are ideal when 100% accuracy is desired, thus resulting to data exact in values. **Hybrid Computers-** Incorporate in a single machine the capabilities of the analog and digital computers. They are used in space vehicle simulations and training of astronauts. C. According to Capacity Capacity refers to : Amount of data that can be stored in memory Speed of internal operation of the computer Capacity of storage devices Number and types of peripheral devices Microcomputers Small computers which are portable. Uses microprocessor (the CPU on a chip), ROM and RAM. It sometimes known as a "Single-Chip Processor" or a "System-on-a-Chip". Examples: Desktop and floor standing units, luggable, laptops, notebooks, subnotebooks, pocket PCs, and pen computers. Minicomputers Machine which are in the middle of microcomputers and mainframes in terms of cost and capability. These act as "servers" which are connected to several workstations or terminals. Mainframe The oldest category, these are air-cooled computers bigger in sizes, about the size of a jeep. They are used mostly by banks, airlines, and insurance companies that handles millions of transactions. Supercomputers The biggest and fastest computers. They can perform 50 million instructions per second and are used in applications such as nuclear weapon development and accurate weather forecasting. In addition, it is used to process very large amounts of information including processing information to predict hurricanes, to generate satellite images and navigation points, and to process military war scenarios. Pre-Modern Era Manual-Mechanical Device These are devices powered by hand and requires physical effort from the user. Examples: **Abacus-** The first man-made computing device that uses beads; invented in China. **Napier's bones-** An arrangement of bones wherein numbers are printed; invented by John Napier. **Oughtred's Slide Rule-** Consists of movable bars with a precise scale which uses approximations for solving problems; invented by William Oughtred. **Pascaline-** The first mechanical calculator ( adding machine ) that uses cogged wheels; invented by Blaise Pascal. **Leibnitz Calculator** The improved Pascaline which could multiply and divide; invented by Gottfried Leibnitz. **Babbage's Difference and Analytical Engines-** These engines embodied most of the design of modern computers. The Difference Engine which can compute tables and the Analytical engine which is completely automatic and capable of calculating any mathematical problems; invented by Charles Babbage. **Electro-mechanical Devices** These are devices powered by an electronic motor and use switches and relays. Examples: **Holllerith's Punch Card Machine**- The first use of punched cards to store data; developed by Herman Hollerith. **Automatic Weaving Loom**- Uses the concept of punched card to control his looms; by Joseph Marie Jacquard. **Automatic Sequence Controlled Calculator (MARK I)-** The first genera-purpose computer; invented by Howard Aiken. **Electronic Devices**- These are devices which use only electrical switches and circuitry instead of mechanical relays. Their principal components are circuit boards, transistors or silicon chips: Examples: **ABC (Atanasoff -- Berry Computer)-** The first special-purpose digital computer that solves simultaneous equations; developed by John Atanasoff. **Electronic Numerical Integrator and Calculator (ENIAC)-** The first fully electronic general-purpose digital computer ever completed by John Eckert and John Mauchly. **Electronic Discrete Variable Computer(EDVAC)-** The completely internally programmed machine. This is simply the enhancement of ENIAC to overcome its limitations. **Electronic Delayed Storage Automatic Computer (EDSAC)-** Also known as Electronic Binary Digital computer that uses binary representation of data and internally stored program; developed by John Eckert and John Presper. First Generation Computers ( 1951 -- 1958 ) Major Hardware Features: Vacuum tubes and magnetic drums Processing Speed: 1,000 instructions per second Size: Mainframes only Examples: **Universal Automatic Computer (UNIVAC I )** -- the first commercial business computer, developed by John Eckert and John Mauchly. IBM 701 -- the first generation computer of IBM IBM 650 -- the most popular generation compute Second Generation Computers ( 1959 -- 1963 ) Major Hardware Features: Transistors and magnetic core Processing Speed: 1,000,000 instructions per second Size: Mainframes only Examples: TRADIC -- first transistorized computer UNIVAC II IBM 7070,7090 AND 1400 series Third Generation Computers ( 1964 -- 1971 ) Major Hardware Features: Integrated circuits or "chips" Processing Speed: 10,000,000 instructions per second Size: Mainframes only Examples: IBM System 360 -- the most significant 3rd generation Computer Burroughs B5500 Fourth Generation Computers ( 1971 -- 1979 ) Major Hardware Features: Microprocessors or Large -- second IC Processing Speed: 100,000,000 instructions per second Sized: Mainframes, Minicomputers, and Microcomputers Examples: Apple II; TRS 80 IBM System 360, System 3090 IBM PC -- XT base computers IBM PC -- AT base computers Motorolla 68030 based computers Fifth Generation Computers ( 1980-present) Major Hardware Features: Circuitry based on gallium arsenide Processing Speed: 10 to 15 million instructions per second and more Size: Large Computers Evolution of Personal Computer Personal Computer (PC) -- are Integrated Circuit that contains the Arithmetic Logic Unit (ALU) and Control Unit of computer Central Processing Unit. These were created for a limited number of people. Microprocessor -- a single Central Processing Unit (CPU). This determine the types of speed rating expressed in megahertz (MHz) or millions of cycle per second. The rating of power of megahertz is directly proportional to the speed of the processor. Thus, this is given the task of determining the computer power of the system and is considered the brain of the computer. Developmental Stage (1974-1977) Example: MITS Altair Early Adopter Stage (1977-1981) Example: Early Apple II Model Corporate Stage (1981-1984) Example: IBM PC Integrated System Stage (1984-1987) Example: Apple Macintosh, IBM AT Networked System Stage (1987-1990) Example: IBM AT, AT & T, Unix Information Age Stage (1990-present) Example: Compuphone, Laptops. DEVELOPMENT OF PERSONAL COMPUTERS First Generation of the Microcomputers 4004 by Intel in 1971 -- the first microprocessor in the world. \- a 4-bit microprocessor, can transfer 4 bits of information at a time. \- the microprocessor is composed of several units and those units communicate with each other and with the outside word by a group of 4 binary paths (called bus), each bit can transmit one bit at a time. Second Generations of the Microcomputers 8008 by Intel in 1972 - the first commercial 8 bit microprocessor it transferred information 8 bits at a time considered the foremost "first generation" 8 bits processor calculator like architecture 8080 in 1973 - enhanced 8008, 2nd generation version of 8008 \- it has more addressing and I/O capability, more instructions and executes instructions faster. 8085 in 1976 - most enhance version of 8080 \- 8 bit microprocessor \- added features as power on reset, vectored interrupts, serial I/O port and a +5 volts. INTEL Major Competitors and the code of their microprocessor Zilog Z80 Motorola 6800 Commodore 6 Third Generations of the Microcomputers 8086 by Intel 1978 -- 16 bit microprocessor was 10 times faster than the most enhanced 8-bit microprocessor. 8088 by Intel in 1979 -- which is internally 16-bit and externally 8-bit compatible \- it the choice of IBM in producing the PC, PC XT 80186 by Intel in 1982 -- (and a companion with 80188) which packs the processing power of 8086 plus support with 15 other chips 80286 by Intel in 1982 -- the microprocessor that controls the IBM PC \- an enhanced 80186 that provides special features necessary for memory management and protection. Pentium -- 32 bits version of microprocessor. Operation Description Take Input The process of entering data and instructions into the computer system. Store Data Saving data and instructions so that they are available for processing as and when required. Processing Data Performing arithmetic, and logical operations on data in order to convert them into useful information. Output Information The process of producing useful information or results for the user, such as a printed report or visual display. Control the workflow Directs the manner and sequence in which all of the above operations are performed. Input Unit  This unit contains devices with the help of which we enter data into the computer. This unit creates a link between the user and the computer. The input devices translate the information into a form understandable by the computer.   Output Unit The output unit consists of devices with the help of which we get the information from the computer. This unit is a link between the computer and the users. Output devices translate the computer\'s output into a form understandable by the users. CPU (Central Proceassing Unit) CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results, and instructions (program). It controls the operation of all parts of the computer. CPU itself has the following three components − - ALU (Arithmetic Logic Unit) - Memory Unit - Control Unit Central Processing Unit (CPU) consists of the following features −  - CPU is considered as the brain of the computer. - CPU performs all types of data processing operations. - It stores data, intermediate results, and instructions (program). - It controls the operation of all parts of the computer. Memory or Storage Unit This unit can store instructions, data, and intermediate results. This unit supplies information to other units of the computer when needed. It is also known as internal storage unit or the main memory or the primary storage or Random Access Memory (RAM). Its size affects speed, power, and capability. Primary memory and secondary memory are two types of memories in the computer. Functions of the memory unit are − - It stores all the data and the instructions required for processing. - It stores intermediate results of processing. - It stores the final results of processing before these results are released to an output device. - All inputs and outputs are transmitted through the main memory. Control Unit This unit controls the operations of all parts of the computer but does not carry out any actual data processing operations. Functions of this unit are − - It is responsible for controlling the transfer of data and instructions among other units of a computer. - It manages and coordinates all the units of the computer. - It obtains the instructions from the memory, interprets them, and directs the operation of the computer. - It communicates with Input/Output devices for transfer of data or results from storage. - It does not process or store data. ALU (Arithmetic Logic Unit) This unit consists of two subsections namely, - Arithmetic Section - Logic Section Arithmetic Section Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication, and division. All complex operations are done by making repetitive use of the above operations. Logic Section Function of logic section is to perform logic operations such as comparing, selecting, matching, and merging of data. Following are some of the important input devices which are used in a computer. Keyboard Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions. Keyboard Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet. The keys on the keyboard are as follows − +-----------------------------------+-----------------------------------+ | | Keys & Description | +===================================+===================================+ | | Typing Keys | | | | | | These keys include the letter | | | keys (A-Z) and digit keys (09) | | | which generally give the same | | | layout as that of typewriters. | +-----------------------------------+-----------------------------------+ | | Numeric Keypad | | | | | | It is used to enter the numeric | | | data or cursor movement. | | | Generally, it consists of a set | | | of 17 keys that are laid out in | | | the same configuration used by | | | most adding machines and | | | calculators. | +-----------------------------------+-----------------------------------+ | | Function Keys | | | | | | The twelve function keys are | | | present on the keyboard which are | | | arranged in a row at the top of | | | the keyboard. Each function key | | | has a unique meaning and is used | | | for some specific purpose. | +-----------------------------------+-----------------------------------+ | | Control keys | | | | | | These keys provide cursor and | | | screen control. It includes four | | | directional arrow keys. Control | | | keys also include Home, End, | | | Insert, Delete, Page Up, Page | | | Down, Control(Ctrl), | | | Alternate(Alt), Escape(Esc). | +-----------------------------------+-----------------------------------+ | | Special Purpose Keys | | | | | | Keyboard also contains some | | | special purpose keys such as | | | Enter, Shift, Caps Lock, Num | | | Lock, Space bar, Tab, and Print | | | Screen. | +-----------------------------------+-----------------------------------+   Mouse Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed. Generally, it has two buttons called the left and the right button and a wheel is present between the buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer.  Advantages - Easy to use - Not very expensive - Moves the cursor faster than the arrow keys of the keyboard. Joystick Joystick is also a pointing device, which is used to move the cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions. Joystick The function of the joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games. Light Pen Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube.  When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU. Track Ball Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved. Track Ball Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button, or a square. Scanner Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation.  Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed. Digitizer Digitizer is an input device which converts analog information into digital form. Digitizer can convert a signal from the television or camera into a series of numbers that could be stored in a computer. They can be used by the computer to create a picture of whatever the camera had been pointed at. Graphic Tablet Digitizer is also known as Tablet or Graphics Tablet as it converts graphics and pictorial data into binary inputs. A graphic tablet as digitizer is used for fine works of drawing and image manipulation applications. Microphone Microphone is an input device to input sound that is then stored in a digital form.  The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music. Magnetic Ink Card Reader (MICR) MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank\'s code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable. Magnetic Ink Card Reader(MICR) This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR is that it is fast and less error prone. Optical Character Reader (OCR) OCR is an input device used to read a printed text.  OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory. Bar Code Readers Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner. Barcode Reader Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to. Optical Mark Reader (OMR) OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.  It is specially used for checking the answer sheets of examinations having multiple choice questions.   Following are some of the important output devices used in a computer. - Monitors - Graphic Plotter - Printer Monitors Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels. There are two kinds of viewing screen used for monitors. - Cathode-Ray Tube (CRT) - Flat-Panel Display Cathode-Ray Tube (CRT) Monitor The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter 'e' in the word help. CRT Monitor A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically. There are some disadvantages of CRT − - Large in Size - High power consumption Flat-Panel Display Monitor The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.  The flat-panel display is divided into two categories − - Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes). - Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device). Printers Printer is an output device, which is used to print information on paper. There are two types of printers − - Impact Printers - Non-Impact Printers Impact Printers Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper. Characteristics of Impact Printers are the following − - Very low consumable costs - Very noisy - Useful for bulk printing due to low cost - There is physical contact with the paper to produce an image These printers are of two types − - Character printers - Line printers Character Printers Character printers are the printers which print one character at a time. These are further divided into two types: - Dot Matrix Printer(DMP) - Daisy Wheel Dot Matrix Printer In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5\*7, 7\*9, 9\*7 or 9\*9) which come out to form a character which is why it is called Dot Matrix Printer. Dot Matrix Printer Advantages - Inexpensive - Widely Used - Other language characters can be printed Disadvantages - Slow Speed - Poor Quality Daisy Wheel Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.  Advantages - More reliable than DMP - Better quality - Fonts of character can be easily changed Disadvantages - Slower than DMP - Noisy - More expensive than DMP Line Printers Line printers are the printers which print one line at a time. Line Printer These are of two types − - Drum Printer - Chain Printer Drum Printer This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute. Advantages - Very high speed Disadvantages - Very expensive - Characters fonts cannot be changed Chain Printer In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters. Advantages - Character fonts can easily be changed. - Different languages can be used with the same printer. Disadvantages - Noisy Non-impact Printers Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers. These printers are of two types − - Laser Printers - Inkjet Printers Characteristics of Non-impact Printers - Faster than impact printers - They are not noisy - High quality - Supports many fonts and different character size Laser Printers These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.  Advantages - Very high speed - Very high quality output - Good graphics quality - Supports many fonts and different character size Disadvantages - Expensive - Cannot be used to produce multiple copies of a document in a single printing Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features. Inkjet Printer They make less noise because no hammering is done and these have many styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also. Advantages - High quality printing - More reliable Disadvantages - Expensive as the cost per page is high - Slow as compared to laser printer A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one. For example, if the computer has 64k words, then this memory unit has 64 \* 1024 = 65536 memory locations. The address of these locations varies from 0 to 65535. Memory is primarily of three types − - Cache Memory - Primary Memory/Main Memory - Secondary Memory Cache Memory Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. It is used to hold those parts of data and program which are most frequently used by the CPU. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.  Advantages The advantages of cache memory are as follows − - Cache memory is faster than main memory. - It consumes less access time as compared to main memory. - It stores the program that can be executed within a short period of time. - It stores data for temporary use. Disadvantages The disadvantages of cache memory are as follows − - Cache memory has limited capacity. - It is very expensive. Primary Memory (Main Memory) Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off. It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory. It is divided into two subcategories RAM and ROM. Primary Memory Characteristics of Main Memory - These are semiconductor memories. - It is known as the main memory. - Usually volatile memory. - Data is lost in case power is switched off. - It is the working memory of the computer. - Faster than secondary memories. - A computer cannot run without the primary memory. Secondary Memory This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.  Characteristics of Secondary Memory - These are magnetic and optical memories. - It is known as the backup memory. - It is a non-volatile memory. - Data is permanently stored even if power is switched off. - It is used for storage of data in a computer. - Computer may run without the secondary memory. - Slower than primary memories. RAM (Random Access Memory) is the internal memory of the CPU for storing data, program, and program result. It is a read/write memory which stores data until the machine is working. As soon as the machine is switched off, data is erased. Primary Memory Access time in RAM is independent of the address, that is, each storage location inside the memory is as easy to reach as other locations and takes the same amount of time. Data in the RAM can be accessed randomly but it is very expensive. RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence, a backup Uninterruptible Power System (UPS) is often used with computers. RAM is small, both in terms of its physical size and in the amount of data it can hold. RAM is of two types − - Static RAM (SRAM) - Dynamic RAM (DRAM) Static RAM (SRAM) The word static indicates that the memory retains its contents as long as power is being supplied. However, data is lost when the power gets down due to volatile nature. SRAM chips use a matrix of 6-transistors and no capacitors. Transistors do not require power to prevent leakage, so SRAM need not be refreshed on a regular basis. There is extra space in the matrix, hence SRAM uses more chips than DRAM for the same amount of storage space, making the manufacturing costs higher. SRAM is thus used as cache memory and has very fast access. Characteristic of Static RAM - Long life - No need to refresh - Faster - Used as cache memory - Large size - Expensive - High power consumption Dynamic RAM (DRAM) DRAM, unlike SRAM, must be continually refreshed in order to maintain the data. This is done by placing the memory on a refresh circuit that rewrites the data several hundred times per second. DRAM is used for most system memory as it is cheap and small. All DRAMs are made up of memory cells, which are composed of one capacitor and one transistor. Characteristics of Dynamic RAM - Short data lifetime - Needs to be refreshed continuously - Slower as compared to SRAM - Used as RAM - Smaller in size - Less expensive - Less power consumption ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture. A ROM stores such instructions that are required to start a computer. This operation is referred to as bootstrap. ROM chips are not only used in the computer but also in other electronic items like washing machine and microwave oven.  Let us now discuss the various types of ROMs and their characteristics. MROM (Masked ROM) The very first ROMs were hard-wired devices that contained a pre-programmed set of data or instructions. These kind of ROMs are known as masked ROMs, which are inexpensive. PROM (Programmable Read Only Memory) PROM is read-only memory that can be modified only once by a user. The user buys a blank PROM and enters the desired contents using a PROM program. Inside the PROM chip, there are small fuses which are burnt open during programming. It can be programmed only once and is not erasable. EPROM (Erasable and Programmable Read Only Memory) EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an EPROM eraser achieves this function. During programming, an electrical charge is trapped in an insulated gate region. The charge is retained for more than 10 years because the charge has no leakage path. For erasing this charge, ultra-violet light is passed through a quartz crystal window (lid). This exposure to ultra-violet light dissipates the charge. During normal use, the quartz lid is sealed with a sticker. EEPROM (Electrically Erasable and Programmable Read Only Memory) EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten thousand times. Both erasing and programming take about 4 to 10 ms (millisecond). In EEPROM, any location can be selectively erased and programmed. EEPROMs can be erased one byte at a time, rather than erasing the entire chip. Hence, the process of reprogramming is flexible but slow. Advantages of ROM The advantages of ROM are as follows − - Non-volatile in nature - Cannot be accidentally changed - Cheaper than RAMs - Easy to test - More reliable than RAMs - Static and do not require refreshing - Contents are always known and can be verified Motherboard serves as a single platform to connect all of the parts of a computer together. It connects the CPU, memory, hard drives, optical drives, video card, sound card, and other ports and expansion cards directly or via cables. It can be considered as the backbone of a computer.   Features of Motherboard A motherboard comes with following features − - Motherboard varies greatly in supporting various types of components. - Motherboard supports a single type of CPU and few types of memories. - Video cards, hard disks, sound cards have to be compatible with the motherboard to function properly. - Motherboards, cases, and power supplies must be compatible to work properly together. Popular Manufacturers Following are the popular manufacturers of the motherboard. - Intel - ASUS - AOpen - ABIT - Biostar - Gigabyte - MSI Description of Motherboard The motherboard is mounted inside the case and is securely attached via small screws through pre-drilled holes. Motherboard contains ports to connect all of the internal components. It provides a single socket for CPU, whereas for memory, normally one or more slots are available. Motherboards provide ports to attach the floppy drive, hard drive, and optical drives via ribbon cables. Motherboard carries fans and a special port designed for power supply. There is a peripheral card slot in front of the motherboard using which video cards, sound cards, and other expansion cards can be connected to the motherboard. On the left side, motherboards carry a number of ports to connect the monitor, printer, mouse, keyboard, speaker, and network cables. Motherboards also provide USB ports, which allow compatible devices to be connected in plug-in/plug-out fashion. For example, pen drive, digital cameras, etc. Memory unit is the amount of data that can be stored in the storage unit. This storage capacity is expressed in terms of Bytes. The following table explains the main memory storage units − +-----------------------------------+-----------------------------------+ | | Unit & Description | +===================================+===================================+ | | Bit (Binary Digit) | | | | | | A binary digit is logical 0 and 1 | | | representing a passive or an | | | active state of a component in an | | | electric circuit. | +-----------------------------------+-----------------------------------+ | | Nibble | | | | | | A group of 4 bits is called | | | nibble. | +-----------------------------------+-----------------------------------+ | | Byte | | | | | | A group of 8 bits is called byte. | | | A byte is the smallest unit, | | | which can represent a data item | | | or a character. | +-----------------------------------+-----------------------------------+ | | Word | | | | | | A computer word, like a byte, is | | | a group of fixed number of bits | | | processed as a unit, which varies | | | from computer to computer but is | | | fixed for each computer. | | | | | | The length of a computer word is | | | called word-size or word length. | | | It may be as small as 8 bits or | | | may be as long as 96 bits. A | | | computer stores the information | | | in the form of computer words. | +-----------------------------------+-----------------------------------+ The following table lists some higher storage units − +-----------------------------------+-----------------------------------+ | | Unit & Description | +===================================+===================================+ | | Kilobyte (KB) | | | | | | 1 KB = 1024 Bytes | +-----------------------------------+-----------------------------------+ | | Megabyte (MB) | | | | | | 1 MB = 1024 KB | +-----------------------------------+-----------------------------------+ | | GigaByte (GB) | | | | | | 1 GB = 1024 MB | +-----------------------------------+-----------------------------------+ | | TeraByte (TB) | | | | | | 1 TB = 1024 GB | +-----------------------------------+-----------------------------------+ | | PetaByte (PB) | | | | | | 1 PB = 1024 TB | +-----------------------------------+-----------------------------------+ early 1980s, the virus creators or virus writers started writing viruses. During the late 1990s, many of the written viruses were just meant to annoy users and to learn how far a virus can spread. These writers were young or teenage programmers who were ignorant of their mischievous acts. Cyber criminals designed computer programs to penetrate and harm computers without user\'s content. It\'s a "malicious software", or popularly known as a Malware. The term malware covers all the types of threats to your computer safety such as spyware, viruses, worms, trojans, rootkits, and etc. Malware performs a wide range of tasks from stealing, encrypting or deleting sensitive data, altering or hijacking core computing functions, and spying on someone\' computer activity without their consent. - Short for malicious software. - A is software used or created to disrupt computer operation, gather sensitive information, or gain access to private computer systems. - It can appear in the form of code, scripts, active content, and other software. - \'Malware\' is a general term used to refer to a variety of forms of hostile, intrusive, or annoying software How Malware Works A cyber criminal can use a vast options of spreading the malware and infect gadgets, computers, and networks. Malware can be delivered using a USB drive, downloading programs, email attachments, and etc. Phishing attacks are another popular type of malware execution. Phony emails are disguised as authentic messages from reputable companies or people. It contains malicious links or attachments that allows threat actors to communicate with the infected systems, exfiltrate sensitive data and even remotely control the compromised device or server.     Usage of Malware - Many early infectious programs, including the first Internet Worm, were written as experiments or pranks. - Today, malware is used primarily to steal sensitive personal, financial, or business information for the benefit of others. - Malware is sometimes used broadly against government or corporate websites to gather guarded information, or to disrupt their operation in general. - However, malware is often used against individuals to gain personal information such as social security numbers, bank or credit card numbers, and so on.   Types of Malware Viruses - A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. - Viruses can also replicate themselves. - All computer viruses are man made. - Viruses copy themselves to other disks to spread to other computers. - They can be merely annoying or they can be vastly destructive to your files. Examples of computer viruses Viruses Vital Information Resource Under Siege These two malicious software are designed to disseminate without the knowledge of the users. The virus attaches itself to a legitimate software. When the software was used, by the computer owner it spreads the virus. A virus needs a human action before they can spread themselves. However, a computer worm spreads without any actions. Examples of computer viruses are:   Resident Viruses - Is a permanent which dwells in the RAM memory. Direct action Viruses-   the main purpose is to replicate and take action when it is executed. Overwrite Viruses-   it deletes the information contained in the files that it infects. Boot Sector Viruses-   A computer virus that infects the sectors on a disk that contain the data a computer uses during the boot process. Macro Viruses -   infect files that are created using certain applications or programs that contains macros. Directory Viruses -   change the paths that indicate the location of the file. Polymorphic Viruses -   encrypt and encode themselves in a different way. File infector / File Viruses -   a type of virus that infect the programs or executable file (.exe or.com). Companion Viruses -   can be considered file infector viruses like resident or direct action type. FAT(File Allocation Table) Viruses -   dangerous, by preventing access to certain sections of the disk.   WORM Write Once Read Many A software program designed to enter a computer system, usually a network, through security \"holes\" and replicate itself. Cyber security flat iconTrojan Horses - A Trojan Horse program has the appearance of having a useful and desired function. - A Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of the computer. - A Trojan Horse must be sent by someone or carried by another program and may arrive in the form of a joke program or software of some sort. - These are often used to capture your logins and Example of Trojan Horses Remote access Trojans (RATs) Backdoor Trojans (backdoors) IRC Trojans (IRCbots) Keylogging Trojans Worms - A computer worm is a self-replicating computer program. - It uses a network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. - It does not need to attach itself to an existing program. Spyware - Spyware is a type of malware installed on computers that collects information about users without their knowledge. - The presence of spyware is typically hidden from the user and can be difficult to detect. - Spyware programs lurk on your computer to steal important information, like your passwords and logins and other personal identification information and then send it off to someone else. Zombie - Zombie programs take control of your computer and use it and its Internet connection to attack other computers or networks or to perform other criminal activities. Phishing - Phishing (pronounced like the word \'fishing\') is a message that tries to trick you into providing information like your social security number or bank account information or logon and password for a web site. - The message may claim that if you do not click on the link in the message and log onto a financial web site that your account will be blocked, or some other disaster. Spam - Spam is email that you did not request and do not want. - One person\'s spam is another\'s useful newsletter or sale ad. - Spam is a common way to spread viruses, trojans, and the like. Adware - Adware (short for advertising-supported software) is a type of malware that automatically delivers advertisements. - Common examples of adware include pop-up ads on websites and advertisements that are displayed by software. - Often times software and applications offer "free" versions that come bundled with adware. Ransomware - Ransomware is a form of malware that essentially holds a computer system captive while demanding a ransom. - The malware restricts user access to the computer either by encrypting files on the hard drive or locking down the system and displaying messages that are intended to force the user to pay the malware creator to remove the restrictions and regain access to their computer. How Malware Spreads? - Malware is a program that must be triggered or somehow executed before it can infect your computer system and spread to others. - Here are some examples on how malware is distributed: 1. a\) Social network 2. b\) Pirated software 3. c\) Removable media 4. d\) Emails e) Websites Damages 1. Data Loss - Many viruses and Trojans will attempt to delete files or wipe hard drives when activated, but even if you catch the infection early, you may have to delete infected files. 2. Account Theft - Many types of malware include keylogger functions, designed to steal accounts and passwords from their targets. - This can give the malware author access to any of the user\'s online accounts, including email servers from which the hacker can launch new attacks. 3. Botnets - Many types of malware also subvert control over the user\'s computer, turning it into a \"bot\" or \"zombie.\" - Hackers build networks of these commandeered computers, using their combined processing power for tasks like cracking password files or sending out bulk emails. 4. Financial Losses - If a hacker gains access to a credit card or bank account via a keylogger, he can then use that information to run up charges or drain the account. Given the popularity of online banking and bill payment services, a hacker who manages to secrete a keylogger on a user\'s system for a full month may gain access to the user\'s entire financial portfolio, allowing him to do as much damage as possible in a single attack. Symptoms - Increased CPU usage - Slow computer or web browser speeds - Problems connecting to networks - Freezing or crashing - Modified or deleted files - Appearance of strange files, programs, or desktop icons - Programs running, turning off, or reconfiguring themselves (malware will often reconfigure or turn off antivirus and firewall programs) Strange computer behavior - Emails/messages being sent automatically and without user's knowledge (a friend receives a strange email from you that you did not send) - There seems to be a lot of network activity when you are not using the network - The available memory on your computer is lower than it should be - Programs or files appear or disappear without your knowledge - File names are changed How Can You Protect Your Computer? - Install protection software. - Practice caution when working with files from unknown or questionable sources. - Do not open e-mail if you do not recognize the sender. - Download files only from reputable Internet sites. - Install firewall. - Scan your hard drive for viruses monthly Using the following techniques: Biometrics -- Biological measurements, such as fingerprinting, that are used in the context of computers to verify a person's identity. User rights -Rules that specify the directories and files that an individual user can access. Key -In the context of data encryption, a key is the method used to encrypt or decipher information as in which numbers in a code match each letters of the alphabet. Trap door -A way to bypass the normal security precautions and enter a computer system. It is often created during computer installation and testing but should be removed before the computer is placed into service. Encryption -The process of scrambling or hiding information so that it cannot be understood without the key necessary to change it back into it's original form. Pretty Good Privacy (PGP) - A popular public key encryption system. Public key encryption (PKE) An encryption method that uses a pair of keys, a public key (known to everyone) that encrypts the message and a private key (known only to the recipient) that decrypts it. Anti-Malware Program - Anti-Malware program is used to prevent, detect, and remove computer viruses, worms, trojan horses and any other type of malware. - Examples of Anti-Malware program:  -- Antivirus program  -- Anti-spyware program -- Anti-spam program -- Firewall Antivirus Program - "Antivirus\" is protective software designed to defend your computer against malicious software. - In order to be an effective defense, the antivirus software needs to run in the background at all times, and should be kept updated so it recognizes new versions of malicious software. Examples of Antivirus Program - - Norton Antivirus - AVG - Kaspersky - Avast! - PC-Cilin - McAffee - Avira   Anti-Spyware Program - Anti-spyware program is a type of program designed to prevent and detect unwanted spyware program installations and to remove those programs if installed. - Examples of Anti-spyware program: -- Spyware Doctor  -- AVG Anti-spyware -- STOPzilla -- Spysweeper   - Anti-spam software tries to identify useless or dangerous messages for you. Firewall - A firewall blocks attempts to access your files over a network or internet connection. - That will block incoming attacks. - Your computer can become infected through shared disks or even from another computer on the network. - So you need to monitor what your computer is putting out over the network or internet also. Terminologies to Remember Crackers -People who break into a computer system with intent to damage files or steal data. Cyberpunks -- People who break into computers, especially Internet computers, to steal data modify files or plant viruses. Hackers -People who are once meant as computer hobbyists or computer novice. Today they are referred to as people who has gained illegal access in a computer system. Data security -Techniques that provide protection for data. Safe computing TIPS 1.Never boot from any devices unless you are sure that it is virus free 2.Check all new software for the presence of viruses 3.If you own laptop, make sure that it is stored in a safe place 4.Keep storage devices containing important information in a safe place. 5.Make it to habit to backup regularly 6.Know the computer that you are using 7.Keep your password secured 8.Avoid letting just anyone use your computer Law of Computer System       1. Contract Law - Software license agreements, including "shrink-wrap" - Business transactions in cyberspace - Contracts for data processing services - Contracts for development of custom software or hardware   2. Copyright Law - Copyright protection for computer software - Copyright protection for text or pictures on Internet   3. Trademark Law - Domain name disputes - Infringement or dilution of trademarks on Internet   4. Patent Law 1. Patent for novel software 2. Patents for computer hardware   5. Tort Law - Defamation - Trade disparagement, unfair competition law - Duty to maintain secure data   6. Computer crime - Unauthorized use of services - Denial of services attacks on websites - Larcency, malicious mischief, vandalism etc. - Fraud (scam) - Malicious computer programs (computer viruses, trojan, worm) - Obscenity, harassment by e-mail   7. Utility Law or Telecommunication Law - Tariffs for Internet traffic via long-distance telephone carrier - Possible regulation of Internet Services Providers   8. Constitutional Law - Freedom of Speech on the Internet - Search and Seizure Law - - HTML is a markup language for describing web documents (web pages). - HTML stands for Hyper Text Markup Language - A markup language is a set of markup tags - HTML documents are described by HTML tags - Each HTML tag describes different document content Example 1 \\ \\ \My First Heading\\ \My first paragraph.\\ \\ \    HTML Tags - - HTML tags are keywords (tag names) surrounded by angle brackets: \content\ - - HTML tags normally come in pairs like \ and \ - The first tag in a pair is the start tag, the second tag is the end tag - The end tag is written like the start tag, but with a slash before the tag name  HTML Editors - - [Adobe DreamweaverLinks to an external site.](http://editor.docx/) - [Microsoft Expression WebLinks to an external site.](http://editor.docx/) - [CoffeeCup HTML EditorLinks to an external site.](http://editor.docx/)    Create your First Web Page using Notepad Step 1: Open Notepad Open Notepad  Step 2: Write sample HTML codes Example: \\ \\ \My First Heading\\ \My first paragraph.\\ \\ \ Step 3: Save the HTML Page File -\> Save as use either the.htm or the.html file extension.  Step 4: View HTML Page in Your Browser Double-click your saved HTML file.    HTML Headings \ \ \This is heading 1\ \This is heading 2\ \This is heading 3\ \This is heading 4\ \This is heading 5\ \This is heading 6\ \ \    HTML Paragraphs \ \ \This is a paragraph.\ \This is a paragraph.\ \This is a paragraph.\ \ \    HTML Images \ \ \ \ \    HTML Elements HTML elements are written with a start tag, with an end tag, with the content in between: \content\ The HTML element is everything from the start tag to the end tag: \My first paragraph.\    Nested HTML Elements 4 HTML elements: \ \ \My First Heading\ \My first paragraph.\ \ \    HTML Example Explained - - The \element defines the whole document. - It has a start tag \ and an end tag \. - The element content is another HTML element (the \ element).   - - The \element defines the document body. - It has a starttag \ and an endtag \. - The element contentis two other HTML elements (\ and \).   - - The \element defines a heading. - It has a starttag \ and an endtag \. - The element contentis: My First Heading.   - The \element defines a paragraph. - It has a starttag \ and an endtag \. - The element contentis: My first paragraph.    HTML Headings Headings are defined with the \ to \ tags. - - \ defines the most important heading. - \ defines the least important heading. Example 2 \ \ \This is heading 1\ \This is heading 2\ \This is heading 3\ \This is heading 4\ \This is heading 5\ \This is heading 6\ \ \    HTML Horizontal Rules \ \ \The hr tag defines a horizontal rule:\ \ \This is a paragraph.\ \ \This is a paragraph.\ \ \This is a paragraph.\ \ \    HTML \ Element - - The HTML \element has nothing to do with HTML headings. - The HTML \ element only contains meta data. - The HTML \ element is placed between the \ tag and the \ tag Example 3 \ \   \My First HTML\   \ \ \ \The HTML head element contains meta data.\ \Meta data is data about the HTML document.\ \ \    HTML Tag Reference    HTML Paragraphs - - HTML documents are divided into paragraphs. - Paragraphs are defined with the \ tag. Example 4 \ \ \This is a paragraph.\ \This is a paragraph.\ \This is a paragraph.\ \ \    HTML Line Breaks - Use the \ tag if you want a line break (a new line) without starting a new paragraph: Example 5 \ \ \This is\a para\graph with line breaks\ \ \   Example 6 \ \ \     My Bonnie lies over the ocean.     My Bonnie lies over the sea.     My Bonnie lies over the ocean.     Oh, bring back my Bonnie to me. \ \Note that your browser ignores the layout in the HTML source code!\ \ \