THE IMPORTANCE OF DOCUMENTATION
The computer hardware, software and peripherals will be accompanied by documentation, which explains how the various systems or programs operate.
Documentation: Information needed to develop, use ormaintain computer hardware and software and to permit access and retrieval of the data.
Although documentation usually comes in the form of printed manuals, guide books, it may also come in electronic form, such as in ‘help screens’ contained within the computer software or documentation in data dictionaries and so on. Often, documentation is created when a specific computer application is used. For example, if a government office creates a data base of employees in order to administer payroll, documentation may be created describing how the database was established, what it is to be used for and what data fields have been created. This documentation can be critical to understanding the database system, particularly if it is being managed in an archival environment long after the creators of the system have left.
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Documentation should always be retained.
Disposing of documentation can cause problems in the future, particularly if you have to reload software from the beginning. Documentation can also contain licences for the legitimate use of the software. Therefore it is critical to protect documentation and ensure it is readily available.
PROTECTING AGAINST VIRUSES
Virus: A computer program that is planted in onecomputer and then transferred, hidden in useful information, to one or more other computers with the intention of corrupting or wiping out information in the recipient computer.
Viruses are extremely common. Many different types of viruses exist, ranging from ones that prevent you from opening up word-processed documents through to ones that destroy the entire contents of a hard drive. Viruses can be caught in several ways, for example by exchanging floppy disks, via electronic mail messages and through downloading documents from the Web. Networks make it much easier for viruses to move around. Once a virus gets into an organisation’s computer system it can spread very quickly. New viruses appear each week, so it is essential that users have up-to-date anti-virus software to combat this problem.
If users have software that is unlicenced it could mean that it is ‘pirate’ or ‘bootleg’ software. This is software that has been illegally copied. Software of this nature sometimes contains viruses that can be extremely damaging to computers.
MAINFRAME COMPUTING
Mainframe computing developed at a time when computational power was an expensive and scarce resource. In order to use the expensive computer technologies efficiently, organisations had to share their resources. Many of computerised applications, such as invoicing, purchasing, payroll, accounting and so on, involved the organisation as a whole.
If the original reasons for the mainframe computing model were cost and scarcity of resources, the current reasons for sharing computer power are
• security: the protection of data from outside or unauthorised access
• integrity: the guarantee that the data is not corrupted and that repeatability is achievable using the same applications and data
• system availability: centralised facilities can be operated by teams in shifts
24 hours a day, maximising the investment in IT equipment and allowing large
data processing activities to be carried out efficiently
• data sharing: data input or created in one part of the organisation becomes
available to other parts
• applications: many modern applications, such as personnel management systems, require access to a shared pool of resources.
Today, mainframe computing is no longer an expensive resource; sharing is still a cost -effective means of providing computational power. Recent studies have shown that on a per-user basis, mainframe computing provides the least expensive form of computing.
A mainframe environment involves not just the hardware. The security, integrity and availability of the mainframe system can only be achieved if the computer centre is staffed by people with the necessary skills, operated according to a set of practices and managed with the discipline (that is, the processes and procedures) that ensures the appropriate levels of security, integrity and availability. This is the ‘mainframe environment’.
In a mainframe environment, many people share access to a mainframe computer.
A large central processor is kept in a purpose-built computer centre staffed by personnel responsible for maintaining it. Individuals in the organisation access the mainframe computer through terminals on their desktops in order to share common organisational resources, such as software programs or electronic data. As we use the term today, a mainframe is actually identified more by the ‘environment’ in which the mainframe is operated. In other words, the physical environment: the controlled temperature and humidity and the physical security of having the mainframe behind locked doors.
Mainframe computers are used as tools to support a given ‘business’ application such as
• processing applications for licences
• processing government payroll information
• processing financial accounts
• processing environmental resource information.
In all of these applications, the common denominator is the work process and the rules for undertaking the process. Everyone is undertaking a part of the whole work process and everyone must complete his or her work in accordance with the procedures required to make sure the job is done satisfactorily and the data are complete and consistent.
For example, if ten people are responsible for managing government payroll, each will have a separate responsibility. They will all have access to the same database through the mainframe computer, and each person must complete his or her task adequately before the ‘job’ can be considered complete.
The automation of a given work process, such as processing government payroll information, is often viewed as an information system.
Information system: The combination of information,technology, processes and people brought together to support a given business objective.
The mainframe is the data and application repository for most organisations. It is also the hub for most online business activities. It is believed that mainframes still house 90 per cent of the data major organisations rely on to conduct their business. Despite claims that mainframe technology is dying out, sales of mainframe hardware and software remain steady. The term ‘mainframe’ has always had the image of being something large in size. Yet, however big the early ‘room-filling’ mainframes were, today’s modern versions are no bigger than the size of a household refrigerator. The level of mainframe sophistication has grown over the more than thirty years of its evolution; organisations still recognise its advantages in terms of performance, reliability and security.
NETWORK COMPUTING
A network computing environment is one in which an organisation has linked together personal computers that have been connected into a network.
There are a number of types of computer networks.
Local area network: A computer network locatedwithin a relatively limited area such as a building, agency or university campus. Also known as a LAN.
Wide area network (WAN): A computer network thatcovers a large geographical area.
There are an estimated 25 million computers connected to local area networks world wide. The purpose of networking personal computers and even mainframes together is to permit employees in the organisation to
• communicate with one another as well as others outside the organisation, normally through the use of electronic messages
• access information and services supported on the World Wide Web
• share documents and data
• support various work processes in the organisation based on the automation of specific tasks.
A network environment can range in sophistication from very simple to very complex. Some networks are used to support simple electronic mail communication. In other networks, employees may be able to share documents with each other and carry out the work of their work groups, project teams, etc. by exchanging electronic documents through e-mail. The most sophisticated organisations may have automated entire work processes. For instance, draft documents such as responses to letters sent to senior officials, are sent through various approval levels (such as action officer to manager to director to senior official) without ever being printed onto paper (except perhaps the final version, which needs to be signed by the senior official).
A computer network can be simple and limited to a small number of computers or complex, linking a large number of computers.
A computer that is not connected to a network is referred to as a stand-alone computer. When a computer is physically connected to a local area network, using a cable or other communications channel, the computer becomes a workstation on the network. Each device on the network including workstations, servers, and printers is referred to as a node.
Node: A processing location on a network.
A workstation normally has all of the usual resources found in the personal computing environment (hard drive, software, data and printer). However, users of workstations will also have access to network resources, which typically include application software, storage space for data files, and printers other than those on the local workstation. On a network, the network server typically provides the applications software and storage space for data files.
Network server: A computer that is connected to thenetwork and that ‘serves’ or distributes resources to network users.
Networks use different kinds of servers to carry out specialised functions. For example, a file server is a computer and storage device dedicated to storing files.
File server: A computer that serves or distributesapplication programs and data files to workstations within a computer network. The hard drive of the file server is shared by the workstations on the network.
Any user on the network can store files on the server. Other types of servers include a print server to manage one or more printers and a database server to process database queries.
Most network users will need to understand file servers because this is where they will store their files on the network. A typical local area network uses a powerful PC as a file server. However, a minicomputer or mainframe computer can also be a file server. File servers fall into three categories; dedicated, non-dedicated and application servers.
A dedicated file server is devoted only to the task of delivering programs and data files to workstations. A dedicated file server does not process data or run programs for the workstations. Instead, programs run using the memory and processor of the workstation.
In some cases, a network computer performs a dual role as both file server and workstation. When a non-dedicated file server is used, the computer workstation functions like a normal workstation, but other workstations can access programs and data files from the hard disk of the user’s computer workstation.
An application server is a computer that runs applications software and runs the results of processing to workstations as requested. An application server makes it possible to use the processing power of both the server and the workstation. Use of an application server splits processing between the workstation client and the network server. The method is also referred to as client/server architecture.
Some networks include a host computer, usually a minicomputer or mainframe attached with terminals. A terminal has a keyboard and screen but does not have a local storage device and does no processing on its own. When a terminal is connected to a host computer, all processing takes place on the host.
The software on a local area network typically includes many of the same applications one might use in a personal computing environment, such as word processing, spreadsheet, database management and so on. As the use of networks increase, however, organisations have begun to demand software that facilitate the flow and sharing of documents. This software includes groupware and workflow software.
Groupware: Applications software that supportscollaborative work between a group of users by managing schedules, sharing documents and undertaking intragroup communications.
Essentially, groupware manages a pool of documents and allows users to access those documents simultaneously. A key feature of groupware is document version management which maintains all revisions within a document when more than one group member revises a document.
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Workflow software: Software that automates theprocess of electronically routing documents from one person to another in a specified sequence and time.
Workflow software facilitates a process or a series of steps. Workflow is based on a ‘process-centred model’ as opposed to groupware’s ‘information-centred model’. With workflow software, the focus is on a series of steps. With groupware software, the documents are the focus.
Peer-to-peer network: workstation has responsibilities.
Peer-to-peer networks simply link a number of PCs together with no network server. This is a cheaper way of networking, and while files and printers can be shared the wider advantages of having a network server are lost.
The main advantage of a computer network is that all the users can share resources, rather than have users each maintain his or her own resources. It is not necessary to purchase multiple copies of software; instead a licence can be purchased to use the software within the network which allows everyone to use the program at the same time.
When a computer network is used, finding, retrieving, and storing files on a network is not very different from the process used on a stand-alone computer. However, when using a network, security is much more of an issue. Information is now accessible to a wide group of people, and sensitive or personal information needs to be protected.
An internal network that belongs to an organisation and is accessible only by that organisation’s members is often referred to as an Intranet.
Intranet: An internal computer network that belongs toan organisation and is accessible only by that organisation’s members.
THE INTERNET
The Internet evolved over the past thirty years from a fledging experiment with four computers into a vast information network that connects millions of microcomputers, minicomputers and mainframe computers. As of 1998, the Internet had more than 100 million users world wide, and that number is growing rapidly. The Internet is decentralised by design and, remarkably, this anarchy by design works well.
Internet: A collection of local, regional and nationalcomputer networks that are linked together to exchange data and distribute processing tasks.
There are a variety of ways to access the Internet, the most common being through an Internet Service Provider (ISP). An ISP is a company that charges an ongoing fee for providing Internet access to businesses, organisations and individuals. The ISP provides the user with the necessary communications software (such as e-mail) and user account. The user supplies a modem that connects the computer to the user’s phone line. The user’s computer dials the ISP’s computer and establishes a connection over the phone line. Once connected the ISP routes data between the user’s computer and the Internet. Most ISPs offer dial-up Internet connections and electronic mail access, along with additional services. Some ISPs offer direct access to the Internet without the use of proprietary software.
The Internet connects millions of people through a collection of computer networks.
A connection that uses a phone line to establish a temporary connection to the Internet is referred to as a dial-up connection. When the user’s computer hangs up, the connection is broken. A phone line provides a very narrow pipe for transmitting data. Its typical capacity is only 28.8 thousand bits per second (bps). Using a phone line, the time to transfer the contents of a 680 megabyte CD-ROM would be over 53 hours. More rapid digital data transmission is now available from some telecoms providers in various parts of the world.
The World Wide Web was created in 1990 as an easy-to-use source of information.
World Wide Web: A computer network system thatallows users to browse through information available on computers round the world.
The World Wide Web opened the Internet to millions of people interested in finding information. There are over one million Web sites around the world and the number is growing very quickly. The World Wide Web consists of documents called Web pages that contain information on a particular topic. A Web page might also contain one or more links that point to other Web pages.
Link: A reference to another document in anenvironment like the World Wide Web, that users can go to directly by clicking on the on-screen reference with the computer’s mouse.
Links make it easy to follow a thread of related information, even if the pages are stored on computers located in different countries. Every Web page is stored as an HTML (HyperText Markup Language) document.
HyperText Markup Language (HTML): One of themain standards that controls how the World Wide Web works; it is an SGML document type definition that determines how Web pages are formatted and displayed and thus enables information to be exchanged on the World Wide Web.
Standardised General Mark-up Language (SGML): Ametalanguage that can be applied to documents in order to maintain their structure and context.
An HTML document contains special instructions called HTML tags that tell a Web browser how to display the text, graphics, and background of a Web page.
Web browsers are used to view Web pages, transfer files between computers, access commercial information services, send e-mail, and interact with other Internet users.
Web browser: A software application that enables auser to locate and view pages on a Web site. Also known as a browser.
To request a Web page the user either types in the URL (Uniform Resource Locator) address or uses a ‘mouse’ to click on a Web page link.
Uniform Resource Locator (URL): The global addressof documents and other resources on the World Wide Web. URLs can point to executable files that can be fetched using FTP (file transfer protocol, ftp://) or a Web page that can be retrieved using HTTP (hypertext transfer protocol, http://).
After the http://, the next segment of the address is the server name. The server is the computer and software that make the data available. A Web server, for instance, is a computer that uses Web server software to transmit Web pages over the Internet. Most Web servers have domain names prefixed with WWW. By entering the Web server name, one accesses the site’s home page.
Home page: The main page of a Website. Typically,the home page serves as an index or table of contents to other documents stored at the site (that is, the address).
Website: A location on the World Wide Web.
A home page is similar to the title page and table of contents in a book. It identifies the site and contains links to other pages at the site. The following is an example of a home page belonging to the ICA, viewed using a particular type of browser software called Microsoft Explorer.
The Web browser is the gateway to commercial information services as well as the free sites on the Internet. A commercial information service provides access to computer-based information for a fee. In 1997, approximately 17 million people subscribed to the top four commercial information services: America On-Line, Compuserve, Microsoft Network and Prodigy.
The server sends the data for the Web page over the Internet to the computer. The data includes two things: the information the user wants to view and a set of instructions that tells the browser how to display it. The instructions include specifications for the colour of the background, the size of the text, and the placement of the graphics. Additional instructions tell the browser what to do when the user clicks on a link. The browser’s menu and tool bars help users navigate the Web as they follow the links. The Back and Forward buttons trace and retrace the users’ path through the links being followed from one Web page to another. The browser stores and can display a list of the pages being visited during each session. The browser can also store a list of favourite sites, often called bookmarks, to permit the user to jump directly to the site they wish to see instead of having to enter its URL every time.
Users can find information on the Web by using a search engine. There are a number of Web sites that provide search facilities, and the Internet Service Provider will links to these sites.
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Search engine: A program that searches documents forspecified keywords and returns a list of documents where the keywords were found.
u eG1sTI9BT8MwDIXvSPyHyEjcWEI2qtE1nRgSRyQ2OLBb2npttcYpTbYVfj3uCW7v2U/Pn7P16Dpx xiG0ngzczxQIpNJXLdUGPt5f7pYgQrRU2c4TGvjGAOv8+iqzaeUvtMXzLtaCSyik1kATY59KGcoG nQ0z3yPx7uAHZyPboZbVYC9c7jqplUqksy3xhcb2+NxgedydnIHN43Lz9bag159tscf9Z3F80IMy 5vZmfFqBiDjGvzBM+IwOOTMV/kRVEB17pRdzzhrQc81iiiidsCqmUZKAzDP5/4v8FwAA//8DAFBL AQItABQABgAIAAAAIQC2gziS/gAAAOEBAAATAAAAAAAAAAAAAAAAAAAAAABbQ29udGVudF9UeXBl c10ueG1sUEsBAi0AFAAGAAgAAAAhADj9If/WAAAAlAEAAAsAAAAAAAAAAAAAAAAALwEAAF9yZWxz Ly5yZWxzUEsBAi0AFAAGAAgAAAAhAC6X4zubAgAACwUAAA4AAAAAAAAAAAAAAAAALgIAAGRycy9l Mm9Eb2MueG1sUEsBAi0AFAAGAAgAAAAhAH2ZEEnfAAAADQEAAA8AAAAAAAAAAAAAAAAA9QQAAGRy cy9kb3ducmV2LnhtbFBLBQYAAAAABAAEAPMAAAABBgAAAAA= " o:allowincell="f" fillcolor="black" stroked="f"> COMPUTER APPLICATIONS
Applications software includes programs that users access to carry out work. This lesson examines two applications that may be of particular use to the student: databases and electronic mail (‘e-mail’). It introduces key concepts related to how databases and e-mail work.
Please remember, this lesson is not intended to provide a comprehensive explanation of the technical details of all applications. Other applications would be word processing, spreadsheets and presentations. A brief description of these types of software can be found in Lesson 1.
DATABASES
A database is a collection of information stored on one or several computers.
Database: A structured assembly of logically relateddata designed to meet various applications but managed independently of them.
More specifically, a database is a self-describing collection of integrated records. A database is self-describing in that it contains, in addition to the user’s source data, a description of its own structure (such as in a data dictionary). It is the data dictionary that make data independence possible (for example, the database management system maps the data fields into records and handles other similar transformation).
A database is a collection of information stored on computers.
In the mid-1960s, large organisations began to apply the power of mainframe database technology to administrative functions. As the term ‘computer’ implies, originally most administrative uses of computers were to process figures rather than text. These were usually activities involving high volumes of numerical calculations, where the workflow was highly predictable and routine. Typical examples include payroll,
accounts administration or personnel data. These database applications were primarily organisation-wide transaction processing systems.
The limitations of file processing prevented the easy integration of data. Database technology held the promise of solving these problems so large organisations began to develop organisational databases. Companies centralised their operational data, such as purchase orders, inventory and accounting data in these databases; these database applications were primarily organisation-wide, transaction processing systems.
Originally, database processing was developed for use in the mainframe environment. However, in the late 1970s to early 1980s, database technology began to move from mainframes to PCs. As a result, database management systems gradually became more powerful and easier to use. By the mid to late-1980s, PCs were beginning to be linked together with the aid of networking, which enabled computers to send data to one another at previously unimaginable rates. In time, users wanted to share their databases as well; this led to the development of multi-user database applications on local area networks (LANs).
Databases were originally developed using mainframe computers but are now common on personal computers and in networked environments.
Following is a brief description of the concept of databases. In order to understand databases, it is important to begin with the data field.
Data field: A space allocated for a particular item ofinformation. In a database, fields are the smallest units of information you can access.
A data field contains a single piece of information (first name, family name, ministry, employee number, salary and so on). A collection of data fields comprise a record such as, in this example, an employee record.
Database record: A complete set of information in adatabase; records are composed of fields, each of which contains one item of information.
A collection of records (in this case, employee records) comprises a database. Structured databases typically store data that describes a collection of similar entities. ‘Salaries and benefits’ is an example of an entity; ‘education/training’ is another entity. A n employee database stores data about the employees in an organisation. A medical database stores data for a collection of patients. An inventory database stores data for a collection of items stocked in a warehouse.
A data structure refers to the overall design for records in a database, such as the fields contained in a certain view and the configuration of fields and sub-fields for data entry. The data structure should present a uniform format to facilitate information exchange.
Data structure: A scheme for organising related piecesof information. The basic types of structures include: files, lists, arrays, records, trees, tables. Each of these basic structures has many variations and allows different operations to be performed on the data.
There are three basic database models.
• Hierarchical databasesexhibit a branching structure, with information arrangedinto sets and sub-sets; getting to a particular piece of data may require going through several vertically ordered files. An example is the process involved in finding a distant cousin on a family tree.
• Network databasesoffer many more direct connections between files, but,similar to hierarchies, the links are predefined and are difficult to change or adjust.
• Object-oriented databaseslink self contained entities (or objects) together.Objects can be text, a picture, a piece of film or any item that can be individually selected and manipulated. This kind of database is particularly useful for organising large amounts of disparate information, but they are not designed for structured numerical analysis.
The limitations found with these types of databases explain why most organisations have turned to relational databases. Relational databases not only accommodate multiple views but allow new links to be forged as needs arise. Relational databases are powerful because they require few assumptions about how data is related or how it will be extracted from the database. As a result, the same database can be viewed in many different ways.
Relational database: A database that spreadsinformation across different tables while maintaining links between them.
A relational database stores facts in tables called relations. The only requirement is that the information must be capable of being laid out in rows and columns (similar to a list of names, addresses and phone numbers). An example from a university might help to illustrate the concept. In a very simplified view of a university database, each facet of the university’s administration would be represented by a table containing information within the remit of a single department. The admissions office, for instance, keeps track of students by ID number, name and major field of study. The personnel office keeps records of the department, rank, names, and social identity numbers of the teaching staff, and so on. The following figure shows examples of relational tables.
A relational database stores information across different tables and connects them with links in the computer.
Isolated from one another, these tables would be nothing more than a simple computerised filing system. Tied together, however, they become a database, with each table offering access to the information held by all of the others. This versatility stems from deliberate duplication of columns in two or more tables, resulting in a tool called a common key. If, for example, two tables containing information about students each possess a column containing student identification numbers (ID) then this number can be used to find the row in each table that contains information applicable to any student.
Each column in a table represents a single data attribute, or characteristic, of the table’s subject. A column might contain, for instance, the identification numbers of the students or each professor’s department.
Each row, or record, in a table contains all the information about a single entry. In the case of a student, a record might include, in addition to an identification number, the individual’s first and last names and major course of study.
Belonging to both a row and a column, an occurrence is the basic unit of a relational database table. The occurrence contains the value of an attribute of a single record. In some cases, the value is a string of letters making up a word or words, in others a set of numerals, such as a student’s identification number or job title.
Officials in the admissions, personnel, and finance offices have direct access to each other’s information through the ‘Dept’ attribute, common to all the tables. Similarly, tables in the admissions and registrar’s offices are joined by the ‘ID’ attribute for the student identification number. Relations in the registrar’s and finance offices are connected by a ‘section’ attribute that identifies subdivisions of courses.
Database management software is used to create and manipulate databases. Data access software is usually used to search databases. The data access software understands the structure and details of the database which means the user simply has to enter his or her search specifications, using either a menu, a keyword search engine, a query language or a natural language (among others).
Menu: A collection of onscreen choices given to theuser tohelp him or her interact with a computer system.
Database menus are similar to those used in most software. They are typically arranged as a hierarchy so that after the user makes a choice at the first level of the menu, a second series of choices appears.
Keyword searching permits access to databases through the use of keywords.
Keyword search engine: A program that allows a userto search a database by an index entry that identifies a specific record or document.
Keyword search engines are especially popular for searching the many documents stored in a free form database such as the World Wide Web. To use a keyword search engine, the user types in a word and the search engine locates areas in the database where the word or related information can be found.
When information in a database needs to be accessed quickly, it is usually stored as a structured database. However, the structure in structured databases can cause a problem for users who might not know the format for the records in a database. One way to help users search structured databases is by providing a ‘query by example’ user interface based on the use of a query language.
Query language: A set of command words that can beused to direct a computer to create databases, locate information, sort records and change the data in those records.
One query language is called SQL (structured query language). The use of query language is based on knowledge of the command word and the grammar or syntax that will let one construct valid query sentences. For example, the SQL command word for finding records is SELECT. WHERE is used to specify that only certain rows of the table are displayed. For example, SELECT employee ID no from employee statistics table WHERE position = ‘Manager’.
In more sophisticated systems, queries can also be formulated in a natural language such as standard English, French, or Japanese. In order to use the natural language, the user is not required to learn a query language. Queries can be straightforward such as: ‘What records of World War Two are available in the archival institution’? This form of searching is still under development although examples of its use are spreading rapidly.
Users can ask questions of the database using a variety of query languages, which formulate questions so that the computer can perform operations and provide results.
COMMUNICATING BY COMPUTER
Communicating via e-mail is rapidly becoming as important as telephone and fax communication and forms an important component of any office automation system.
Electronic mail (e-mail): A way of sending messagesbetween people anywhere within an organisation or in the world using a computer that can communicate with another computer through a computer network. The message or document can be viewed on a computer screen and printed out.
E-mail is handled by a variety of software programs such as Microsoft Outlook Express, Eudora, elm, pine and so on. The message originator creates a message file in the e-mail software editor. When complete, the message is posted to a message transport system that assumes the responsibility for delivering that message to its recipient(s) ‘mailbox’.
To receive and read the message, the recipient runs a software program that retrieves incoming messages, allowing the messages to be filed, listed, forwarded or replied to. Generally a single user-interface program is used to send and receive messages both locally and worldwide. Users do not need to have the same e-mail software program as the person they are corresponding with. The e-mail itself may consist of simply a message or may carry with it attachments containing files created in a variety of software applications, for example word processed documents or spread sheets.
Electronic mail is a method for communicating messages electronically using computer networks.
The ability to send email depends on having an Internet Service Provider and a modem, or being linked into a larger university, government or company network. Being linked into a larger network requires a user to have a network card in the computer and access to network cabling. There are various networking standards. One of the most common is ‘ethernet’.
Ethernet: A local area network (LAN) protocol thatsupports data transfer.
Open networks allow users to send e-mail internally, to colleagues in the same organisation, and externally via the Internet. Some organisations have private networks that allow staff to send e-mail all over the world, but not outside the organisation.
Network administrators or Internet Service Providers will give users an email address. This is usually in the format xxx@yyy.zzz. The first part of the address before the @ sign is the individual user’s name or identifier. The second part of the address is split into at least two parts (sometimes more), each part divided by a full stop or period. This part of the address indicates which company or university the user works for, or which ISP they are using, or even which country they are based in.
For example a user on America-Online would have the address: auser@aol.com. A user in the British University College London may have the email address: zzz999@ucl.ac.uk. In this address, the user has been given the code ‘zzz999’ by the university. The rest of the address shows that ‘ucl’ is University College London, that it is an academic institution (‘ac’) and that it is based in the UK (‘uk’). There are a number of different types of email addresses, including .com, .org, .co.uk and so on.
The following figure is an example of an e-mail message received using Microsoft Outlook Express electronic mail software that includes attachments.