computer science lecture notes for sudents and class notes, Lecture notes of Computer Science

Download computer science lecture notes for sudents and class notes and more Lecture notes Computer Science in PDF only on Docsity! COMPUTER MANUAL ©2017 INTRODUCTION TO COMPUTERS AND WINDOWS What is a computer? A computer is an information-processing machine. It may also be defined PAGE 10 as a device that works under the control of stored programs automatically accepting, storing and processing data to produce information that is the result of that processing. BASIC COMPUTING TERMS Data-Refers to raw facts describing a situation Information – Refers to data that has been assembled into a more useful form or intelligible form e.g. invoices, vouchers, reports e.t.c Binary- A base-2 number system in which values are expressed as combinations of two digits, 0 and 1. Bytes A unit of data that typically holds a single character, such as a letter, a digit, or a punctuation mark. Some single characters can take up more than one byte. COMPUTERS SYSTEM A Computer System is made up of three main components • Hardware • Software • Liveware Hardware are the physical components of a computer e.g. keyboard, printer, mouse, system unit etc. Hardware categories A computer system is a set of integrated devices that input, output, process, and store data and information. Computer systems are currently built around at least one digital processing device. There are five main hardware components in a computer system: the central processing unit (CPU); primary storage (main memory); secondary storage; and input and output devices. Basic elements of hardware The basic elements that make up a computer system are as follows: a) Input Most computers cannot accept data in forms customary to human communication such as speech or hand-written documents. It is necessary, therefore, to present data to the computer in a way that provides easy conversion into its own electronic pulse-based forms. This is commonly achieved by typing data using the keyboard or using an electronic mouse or any other input device. Keyboard can be connected to a computer system through a terminal. A terminal is a form of input and output device. A terminal can be connected to a mainframe or other types of computers called a host computer or server. There are four types of terminals namely dumb, intelligent, network and Internet. PAGE 10 Monitors – Output device for soft-copy output (temporal screen display of output which lasts as long as the monitor’s power is on). They are the most frequently used output devices. Some are used on the desktop; others are portable. Two important characteristics of the monitor are size and clarity. Voice-output devices 1 Voice-output devices make sounds that resemble human speech. Voice-output devices use prerecorded vocalized sounds to produce output. The computer “speaks” synthesized words. Voice output is not as difficult to create as voice input. Most widely used voice-output devices are stereo speakers and headphones. Devices are connected to a sound card in the system unit. Sound card is used to capture sound as well as play it back. Examples of voice output uses: Soft-drink machines, the telephone, and in cars. Voice output can be used as a tool for learning. Can help students study a foreign language. Used in supermarkets at the checkout counter to confirm purchases. Most powerful capability is to assist the physically challenged. Auxiliary/Secondary Storage devices Secondary storage devices store a larger amount of data or instructions than does main memory, on a more permanent basis. On a per megabyte basis, secondary storage is also cheaper than primary storage. Secondary storage is also infinitely extendable, unlike main memory, which is finite. Secondary storage is not volatile. Secondary storage is also more portable than primary storage – that is, it is possible to remove it from a computer and use the device and its contents in another. Types of secondary storage devices 1 Magnetic disks – Stores bits as magnetic spots. Magnetic disks are similar to magnetic tapes in that areas are magnetized to represent bits. However the disks’ read/write head can go directly to the desired record, allowing fast data retrieval. Magnetic disks can range from small and portable, such as diskettes with 1.44MB of storage capacity, to large capacity fixed hard disks, which are more expensive and less portable. o Floppy disks (diskettes) § 5 ¼ floppy disks § 3 ½ floppy disks – The most common size with a capacity of 1.44 MB. They are not very fast and durable. o Hard disks/Fixed disks – Also called hard drives. Their capacity range from 20 to 120 GB. They are fast and durable though not foolproof. Most are internal, but disks that use removable cartridge are available. Disk compression can be used to increase capacity but slows performance. 2 Optical Disks – Store bits as “pits” and “lands” on surface of disk that can be detected (read) by a laser beam. o CD-ROM (Compact-Disk Read Only Memory) – Only read and cannot be erased for rewriting. Has a capacity of 650 MB PAGE 10 o CD-R (Compact-Disk Recordable) / WORM (Write Once, Read Many) – Usually blank at first and can be written only once. Has a capacity of 650 MB o CD-RW (Compact Disk ReWritable) – Can written and read more than once. Has a capacity of 650 MB. o DVD-ROM (Digital Video Disks) – They are similar to CDs except that it has high quality sound and high-resolution video. Has a normal capacity of 4.7 GB and up to 17 GB if double-sided with double layering. Uses laser technology. They are a relatively new technology usually used in the entertainment industry. Storage capacity abbreviations 1 KB - kilobyte - 1000 (thousand) MB - megabyte - 1,000,000 (million) GB - gigabyte - 1,000,000,000 (billion) TB - terabyte - 1,000,000,000,000 (trillion) Communication devices 1 Modem - Modems allow computers (digital devices) to communicate via the phone system (based on analog technology). It turns the computers digital data into analog, sends it over the phone line, and then another modem at the other end of the line turns the analog signal back into digital data. 2 Fax/modem - basic digital/analog modem enhanced with fax transmission hardware that enables faxing of information from computer to another fax/modem or a fax machine (NOTE: a separate scanner must be connected to the computer in order to use the fax/ modem to transfer external documents) Computer Memory Memory capability is one of the features that distinguish a computer from other electronic devices. Like the CPU, memory is made of silicon chips containing circuits holding data represented by on or off electrical states, or bits. Eight bits together form a byte. Memory is usually measured in megabytes or gigabytes. A kilobyte is roughly 1,000 bytes. Specialized memories, such as cache memories, are typically measured in kilobytes. Often both primary memory and secondary storage capacities today contain megabytes, or millions of bytes, of space. 1. RAM (Random Access Memory) /RWM (Read Write Memory) – Also referred to as main memory, primary storage or internal memory. Its content can be read and can be changed and is the working area for the user. It is used to hold programs and data during processing. RAM chips are volatile, that is, they loose their contents if power is disrupted. Typical sizes of RAM include 32MB, 64MB, 128MB, 256MB and 512MB. a. EDO – Extended Data Out b. DRAM – Dynamic RAM PAGE 10 c. SDRAM – Synchronous 1. ROM (Read Only Memory) – Its contents can only be read and cannot be changed. ROM chips is non-volatile, so the contents aren’t lost if the power is disrupted. ROM provides permanent storage for unchanging data & instructions, such as data from the computer maker. It is used to hold instructions for starting the computer called the bootstrap program. ROM: chips, the contents, or combination of electrical circuit states, are set by the manufacturer and cannot be changed. States are permanently manufactured into the chip. NB 1. Computer Virus is a malicious program written with the intention of destroying computer resources. 2. CONTROL PANEL-Provides you with options of customizing your computer with its functionality. 3. Software refers to the programs that facilitate the working of a computer system. There are two types of software namely: • System software e.g. Operating System • Application software Operating System refers to that software responsible for starting the computer. It is necessary for other programs to run and for the user to interact with the hardware. Commonly used Operating systems are:-MS-DOS (Microsoft Disk Operating System). Windows XP, Windows 2007. STARTING UP A COMPUTER NB: Ensure the power cables are correctly placed in the sockets and they are ON • Press the switch button on system unit and the monitor • The system will boot i.e. Load the operating system from the main memory ready to be used. • Log on to the system. DESKTOP The on-screen work area on which windows, icons, menus, and dialog boxes appear. To change your desktop background 1. Open Display in Control Panel. 2. On the Desktop tab, do one or more of the following: • Click a picture in the Background list. In Position, click Center, Tile, or Stretch. • Click Browse to search for a background picture in other folders or on other drives. You can use files with the following extensions: .bmp, .gif, .jpg, .dib, .png, .htm. In Position, click Center, Tile, or Stretch. PAGE 10 1. On the File menu, click Save As. 2. In the File name box, enter a new name for the file. 3. Click Save Selecting a document view Do any of the following: • Click the View menu to select Normal, Web Layout, Print Layout, Outline, Reading Layout, Document Map, or Thumbnails. • Click the File menu to select either Web Page Preview or Print Preview view. Change the size of text 1. Select the text you want to change. 2. On the Formatting toolbar, type or click a point size in the Font Size box . For example, type 10.5. Adding page numbers 1. On the Insert menu, click Page Numbers. 2. In the Position box, specify whether to print page numbers in the header at the top of the page or in the footer at the bottom of the page. 3. In the Alignment box, specify whether to align page numbers left, center, or right relative to the left and right margins, or inside or outside relative to the inside and outside edges of pages that will be bound. 4. If you don't want a number on the first page, clear the Show number on first page check box. 5. Select any other options you want. Headers and footers • Headers and footers are areas in the top and bottom margins of each page in a document. • You can insert text or graphics in headers and footers— for example, page numbers, the date, a company logo, the document's title or file name, or the author's name— that are printed at the top or bottom of each page in a document. • You can work in the header and footer areas by clicking Header and Footer on the View menu Tables A table is made up of rows and columns of cells that you can fill with text and graphics. Tables are often used to organize and present information. PAGE 10 Creating a table 1. Click where you want to create a table. 2. On the Table menu, point to Insert, and then click Table. 3. Under Table size, select the number of columns and rows. 4. Under AutoFit behavior, choose options to adjust table size. 5. To use a built-in table format, click AutoFormat. Select the options you want. Add a cell, row, or column to a table 1. On the Table menu, point to Insert, and then click an option. Note • To quickly add a row at the end of a table, click the last cell of the last row, and then press the TAB or ENTER key. • To add a column to the right of the last column in a table, click in the last column. On the Table menu, point to Insert, and then click Columns to the Right. • You can also use the Draw Table tool to draw the row or column where you want. Word Art You can insert decorative text by using Insert WordArt on the Drawing toolbar. You can create shadowed, skewed, rotated, and stretched text, as well as text that has been fitted to predefined shapes. Because a special text effect is a drawing object, you can also use other buttons on the Drawing toolbar to change the effect— for example, to fill a text effect with a picture. Drawings Use the Drawing toolbar to add any shapes or pictures that you want. Add bullets or numbering Bullet: A dot or other symbol that is placed before text, such as items in a list, to add emphasis.) or numbers to existing lines of text. Add bullets or numbering to existing text 1. Select the items you want to add bullets or numbering to. 2. On the Formatting toolbar, click Bullets or Numbering . . Hide All PAGE 10 Printing a document • Click Print Preview on the Standard toolbar. To exit print preview (print preview: A view of a document as it will appear when you print it.) and return to the previous view of the document, click Close. Print all or part of a single document • Print a range of pages 1. On the File menu, click Print. 2. Under Page range, specify the portion of the document you want to print. If you click Pages, you must also enter the page numbers or page ranges you want to include, or both. Note You can also select the portion of the document you want to print. Click Print on the File menu, and then click Selection. • Print only odd or even pages 1. On the File menu, click Print. 2. In the Print box, click either Odd pages or Even pages. Print specific pages and sections 1. On the File menu, click Print. 2. Under Page range, click Pages. 3. In the Pages box, type instructions to print one of the following: EXERCISE 1 JUHUDI COLLEGE OF SCIENCE AND TECHNOLOGY O R G A N I Z A T I O N C H A T PAGE 10 Row and column headings –Indicates particular column letter or row number tab Worksheet-Is the working area in Ms excel. Cell –Is the intersection between a row and a column.One cell is always active.This is the cell where data can be entered.A thicker border identifies an active cell.A cell can be made active by using the Arrow keys .tab key and the enter key. ENTERING & EDITING DATA IN A WORKSHEET ENTERING DATA • Click on the cell where you want to enter the data and type • Click on the cell and click on the formula bar and type the data then Enter Entering data exercise Name Eng Kis Geo Total Dan 45 78 78 Kibet 78 45 45 Sam 45 56 45 Kiget 78 11 89 Daniel 89 12 12 Kirui 12 23 56 Sarah 45 80 48 sammy 78 88 78 COPYING, MOVING AND DELETING CELL ENTRIES • First select/Highlight • Go to edit menu and click copy • Click on a cell to copy and go to edit menu and click paste USING AUTO FILL Used to create a series of incremental/decrement values or fixed values on a worksheet by dragging the fill handle with the mouse To use, an incremental value is first established then the fill handle is used. Nb Move pointer t o he corner of the cell to get the fill handle [Black + sign) Formatting the worksheet From the menu bar format, cells…which has tabs for fonts,pattern,borders numbers,etc PAGE 10 WORKING WITH FORMULAS A formula is a sequence of values, cell refernces,names,functions or operators in a cell that produces a new value from existing values. A formula always begins with an equal sign(=). For example =B4 + B5 =sum (C4:C8 =Average (E7:E9) CHARTS AND GRAPHS A chart is a graphic representation of worksheet data. Chart wizard-is a series of dialog boxes that guides to create a chart or modify settings of an existing chart Creating Chart Open a new workbook and type in the following table QTR1 QTR2 QTR3 QTR4 FILA 230 345 460 575 PUMA 260 380 500 620 REEBOX 290 415 540 665 NIKE 320 450 580 710 SAVE THE WORKBOOK AS SPOTY MICROSOFT ACCESS INTRODUCTION TO ACCESS 1. Access is a relational database manger with strong object oriented qualities. PAGE 10 2. Access stores all objects (such as multiple tables, queries, forms, report and macros) in one file ACCESS CONCEPTS 1. Database is a collection of objects used to store your data. 2. Tables are collections of data arranged in rows of records and columns of fields. 3. Queries once your data has been stored in the form of tables, you can obtain specific subsets (dynasets in Access) of that data by using queries. 4. Forms are used to display the data stored in tables or queries. Forms routinely are used for adding a new data to a table and for editing or displaying existing data, usually in a one-record at a time format. 5. Reports-the desired result of any database is to provide information reports. You can print reports from table or form queries, in virtually any desired format. 6. Macros-They are groups of instructions that accomplish a specialized task.When you run a macro Access sequentially carries out the list of instructions. 7. Modules. If programming is necessary, you can write modules, which are collections of code using Basic programming language. WORKINGWITH ACCESS 1. Click start button, go to programs, Microsoft office and click Microsoft Access. 2. Access loads in a document and you will see the Microsoft Access start-up window and a dialog box prompting you for creating or opening a database 3. Click “Blank Database” option since you are creating a new database. 4. The file New Database window appears. Enter the name of the database you to create. 5. A blank database window shown below appears. WORKING WITH TABLES Creating Tables To create a blank (empty) table for entering your own data, you can: • Create a table in Design view, where you can add fields, define how each field appears or handles data, and create a primary key • Use the Table Wizard to choose the fields for your table from a variety of predefined tables such as business contacts, household inventory, or medical records. • Enter data directly into a blank datasheet. When you save the new datasheet, Microsoft Access will analyze your data and automatically assign the appropriate data type and format for each field. PAGE 10 • Design template Base your presentation on a PowerPoint template that already has a design concept, fonts, and color scheme. In addition to the templates that come with PowerPoint, you can use one you created yourself. • Templates with suggested content Use the AutoContent Wizard to apply a design template that includes suggestions for text on your slides. You then type the text that you want. • A template on a Web site Create a presentation using a template located on a Web site. Insert a new slide 1. To insert a new blank slide, do either of the following: • On the Formatting toolbar, click New Slide . • With the insertion point in the Outline or Slides tab, press Enter. 2. In the Slide Layout task pane, click the layout you want. Apply a slide layout 1. On the Format menu, click Slide Layout. 2. On the Slides tab in normal view, select the slides you want to apply a layout to. 3. In the Slide Layout task pane, point to the layout you want, and then click it. Delete a slide 1. On the Outline tab or Slides tab in normal view, select the slides you want to delete. (If you want to select slides in order, press SHIFT as you click; for slides not in order, press CTRL as you click.) 2. On the Edit menu, click Delete Slide. Transition One of a set of transitional display effects that are available in some Microsoft Office applications. Transitions specify how the display changes (such as fading to black) as a user moves from one item (such as slide or Web page) to another.) Add transitions between slides A) Add the same transition to all slides in a slide show presentation 1. On the Slide Show menu, click Slide Transition. 2. In the list, click the effect you want. 3. Click Apply to All Slides. B) Add different transitions between slides PAGE 10 Repeat the following process for each slide you want to add a different transition to. 1. On the Slides tab in normal view, select the slides you want to add a transition to. 2. On the Slide Show menu, click Slide Transition. 3. In the list, click the transition effect you want. Set timings for a slide show Set timings manually Repeat the following process for each slide you want to set the timing for. 1. On the Slides tab in normal view, select the slides you want to set the timing for. 2. On the Slide Show menu, click Slide Transition. 3. Under Advance slide, select the Automatically after check box, and then enter the number of seconds you want the slide to appear on the screen. Record timings while you rehearse 1. On the Slide Show menu, click Rehearse Timings to start the show in rehearsal mode. 2. Click the advance button when you're ready to go to the next slide. 3. When you reach the end of the slide show, click Yes to accept the timings or No to start over. ANIMATION SCHEMES Animate is to add a special visual or sound effect to text or an object. For example, you can have your text bullet points fly in from the left, one word at a time, or hear the sound of applause when a picture is uncovered.) • You can animate text, graphics, diagrams, charts, and other objects on your slides so that you can focus on important points, control the flow of information, and add interest to your presentation. To simplify designing with animations, apply a preset animation scheme to items on all slides, selected slides, or some items on the slide master. Or, you can control how and when you want an item to appear on a slide during your presentation— to fly in from the left when you click the mouse, for example— using the Custom Animation task pane. Custom animations can be applied to items on a slide, in a placeholder, or to a paragraph (which includes single bullets or list items). For instance, you can apply the fly-in animation to all items on a slide or you can apply it to a single paragraph in a bulleted list. Use entrance, emphasis, or exit options, in addition to preset or custom motion paths . Also, you can apply more than one animation to an item; so, you can make that bullet item fly in and then fly out. PAGE 10 Most animation options include associated effects to choose from. These might include options for playing a sound with the animation, and text animations usually let you apply the effect by letter, word, or paragraph (such as having a title fly in a word at a time instead of all at once). You can preview the animation of your text and objects for one slide or for the whole presentation. Create a custom show 1. On the Slide Show menu, click Custom Shows, and then click New. 2. Do one of the following: Create a custom show 2..1 Under Slides in presentation, select the slides you want to include in the custom show, and then click Add. To select multiple slides, hold down CTRL as you click the slides. 2..2 To change the order in which slides appear, select a slide under Slides in custom show, and then click one of the arrows to move the slide up or down in the list. 2..3 Type a name in the Slide show name box, and then click OK. 2..4 Repeat steps 1 through 3 to create more custom shows with any slides in your presentation. EXERCISE 1 EXERCISE 2 PAGE 10 MICROSOFT PUBLISHER PARTS OF MICROSOFT PUBLISHER WINDOW Create a publication 1. On the File menu, click New. 2. In the New Publication task pane.Under New from a design, do one of the following: • To create a publication that you want to print, click Publications for Print. Then, under Publications for Print, click the type of publication you want to create. • To create a Web site or a publication you plan to send as an e-mail message, click Web Sites and E-mail. Then click Web Sites or E-mail, and click the type of publication you want. 3. In the Preview Gallery, click the design you want. 4. Do any of the following: • To change the publication's overall design, click Publication Designs in the task pane. • To change the publication's color scheme, click Color Schemes in the task pane. • To change the publication's font scheme, click Font Schemes in the task pane. PAGE 10 • If you are creating a Web page, newsletter, or catalog, to change page content options, click Page Content. • Change or select any additional options in the task pane for the type of publication you have created. 5. In your publication, replace the placeholder text and pictures with your own or with other objects. 6. On the File menu, click Save As. 7. In the Save in box, select the folder where you want to save the new publication. 8. In the File name box, type a name for your publication. 9. In the Save as type box, select Publisher Files. 10. Click Save. Create a publication from a design set 1. On the File menu, click New. 2. In the New Publication, under New from a design, click Design Sets. 3. In the task pane, select the design set you want. 4. In the Preview Gallery, click the type of publication you want. 5. Do any of the following: • To change the publication's overall design, click Publication Designs in the task pane. • To change the publication's color scheme, click Color Schemes in the task pane. • To change the publication's font scheme, click Font Schemes in the task pane. • If you are creating a Web page, newsletter, or catalog, to change page content options, click Page Content. • Change or select any additional options in the task pane for the type of publication you have created. 6. In your publication, replace the placeholder text and pictures with your own or with other objects. 7. On the File menu, click Save As. 8. In the Save in box, select the folder where you want to save the new publication. 9. In the File name box, type a name for your publication. 10. In the Save as type box, select Publisher Files. 11. Click Save. Create a text box 1. On the Objects toolbar, click Text Box . PAGE 10 In your publication, point to where you want one corner of the text to appear, and then drag diagonally until you have the box size you w INTERNET & E-MAIL Internet. A worldwide network of computers. If you have access to the Internet, you can retrieve information from millions of sources, including schools, governments, businesses, and individuals. PAGE 10 Search tools developed for the Internet help users locate precise information. To access a search tool, you must visit a web site that has a search tool available. There are two basic types of search tools available: - Indexes - Search engines Indexes 1 Indexes are also known as web directories They are organized by major categories e.g. Health, entertainment, education etc Each category is further organized into sub categories Users can continue to search of subcategories until a list of relevant documents appear The best known search index is Yahoo Search engines 1 Search engines are also known as web crawlers or web spiders They are organized like a database Key words and phrases can be used to search through a database Databases are maintained by special programs called agents, spiders or bots Widely used search engines are Google, HotBot and AltaVista. Web utilities Web utilities are programs that work with a browser to increase your speed, productivity and capabilities. These utilities can be included in a browser. Some utilities may be free on the Internet while others can be charged for a nominal charge. There are two categories of web utilities: 1 Plug-ins Helper applications Plug-ins 1 A plug-in is a program that automatically loads and operates as part of your browser. Many websites require plug-ins for users to fully experience web page contents Some widely used plug-ins are: o Shockwave from macromedia – used for web-based games, live concerts and dynamic animations o QuickTime from Apple – used to display video and play audio o Live-3D from Netscape – used to display three-dimensional graphics and virtual reality PAGE 10 Helper applications Helper applications are also known as add-ons and helper applications. They are independent programs that can be executed or launched from your browser. The four most common types of helper applications are: 1 Off-line browsers – also known as web-downloading utilities and pull products. It is a program that automatically connects you to selected websites. They download HTML documents and saves them to your hard disk. The document can be read latter without being connected to the Internet. Information pushers – also known as web broadcasters or push products. They automatically gather information on topic areas called channels. The topics are then sent to your hard disk. The information can be read later without being connected to the Internet. Metasearch utilities – offline search utilities are also known as metasearch programs. They automatically submit search requests to several indices and search engines. They receive the results, sort them, eliminate duplicates and create an index. Filters – filters are programs that allow parents or organizations to block out selected sites e.g. adult sites. They can monitor the usage and generate reports detailing time spent on activities. Discussion groups There are several types of discussion groups on the Internet: 1 Mailing lists Newsgroups Chat groups Mailing lists In this type of discussion groups, members communicate by sending messages to a list address. To join, you send your e-mail request to the mailing list subscription address. To cancel, send your email request to unsubscribe to the subscription address. Newsgroups Newsgroups are the most popular type of discussion group. They use a special type of computers called UseNet. Each UseNet computer maintains the newsgroup listing. There are over 10,000 different newsgroups organized into major topic areas. Newsgroup organization hierarchy system is similar to the domain name system. Contributions to a particular newsgroup are sent to one of the UseNet computers. UseNet computers save messages and periodically share them with other UseNet computers. Interested individuals can read contributions to a newsgroup. Chat groups Chat groups are becoming a very popular type of discussion group. They allow direct ‘live’ communication (real time communication). To participate in a chat group, you need to join by selecting a channel or a topic. You communicate live with others by typing words on your computer. Other members of your channel immediately see the words on their computers and PAGE 10 they can respond. The most popular chat service is called Internet Relay Chat (IRC), which requires special chat client software. Instant messaging Instant messaging is a tool to communicate and collaborate with others. It allows one or more people to communicate with direct ‘live’ communication. It is similar to chat groups, but it provides greater control and flexibility. To use instant messaging, you specify a list of friends (buddies) and register with an instant messaging server e.g. Yahoo Messenger. Whenever you connect to the Internet, special software will notify your messaging server that you are online. It will notify you if any of your friends are online and will also notify your buddies that you are online. E-mail (Electronic Mail) E-mail is the most common Internet activity. It allows you to send messages to anyone in the world who has an Internet e-mail account. You need access to the Internet and e-mail program to use this type of communication. Two widely used e-mail programs are Microsoft’s Outlook Express and Netscape’s Communicator. E-mail has three basic elements: (i) Header – appears first in an e-mail message and contains the following information a. Address – the address of the person(s) that is to receive the e-mail b. Subject – a one line description of the message displayed when a person checks their mail c. Attachment – files that can be sent by the e-mail program Message – the text of the e-mail communication Signature – may include sender’s name, address and telephone number (optional) E-mail addresses The most important element of an e-mail message is the address of the person who is to receive the letter. The Internet uses an addressing method known as the Domain Name System (DNS). The system divides an address into three parts: (i) User name – identifies a unique person or computer at the listed domain Domain name – refers to a particular organization Domain code – identifies the geographical or organizational area Almost all ISPs and online service providers offer e-mail service to their customers. The main advantages of email are: 1 It is normally much cheaper than using the telephone (although, as time equates to money for most companies, this relates any savings or costs to a user’s typing speed). Many different types of data can be transmitted, such as images, documents, speech etc. It is much faster than the postal service. Users can filter incoming email easier than incoming telephone calls. It normally cuts out the need for work to be typed, edited and printed by a secretary. It reduces the burden on the mailroom It is normally more secure than traditional methods PAGE 10