Introduction To Computers

What is a computer?

It is one of the most revolutionary and powerful tools ever developed! It stands in the company of the wheel, the aircraft wing and the internal combustion engine because of the tremendous changes it has and still continues to make in our lives.

Together with the its close cousins, the Internet and the web, a global, instantaneous communications network now exists in a way no one dreamed of when the first commercial PC appeared in 1981.

This Web site was developed to help non-technical people take full advantage of this powerful technology. On the surface, its workings are not at all intuitive, and probably appear somewhat mysterious. It is just the opposite! It is a very well ordered, logical machine.

Our aim is to take a some of the mystery out of it for you!

Where do we begin?

There are different ways to study any system. One is by describing each component. In Hardware each component of the PC is described to provide a basic understanding of how each one works. This type of analysis by itself doesn't provide an understanding of the how the PC functions as a unit.

In PC Basics we talk about the different functions in a PC and what they do. At the end we show you the bigger picture where they all come together to make the PC work.

• Processor - At the heart of every PC is the central processing unit, CPU for short. The CPU plugs into a motherboard which has a lot of other chips and electronics on it. The CPU and other components work together to schedule, compute and control everything that happens in the PC.
  
  You've probably seen the 'Intel Inside' appearing in many computer sales ads. They are referring to the Intel CPU which is often a Pentium or Celeron processor.

• Input - devices that allow you to direct the action of the PC. The keyboard and mouse enable you to control the computer by giving it directions (input).

• Output - devices that display or produce results for you. The video display and printer are the primary ones. The speakers beep, chime etc., to let you know an action is completed and they also play your favorite MP3 files.

• Memory - is temporary storage used by the CPU to store results of calculations or files brought in from the hard drive. Memory is very fast and volatile which means it loses it's information when power is removed. The memory cells are housed in Integrated Circuits (ICs), or chips as they are often called.

• Storage - devices that retain information magnetically (Hard Disk Drive and Tapes) or optically (CD and DVD). They are not as fast as memory but can store much more data. They do not lose their information when power is removed.

• Software - these are instructions, also known as programs or code. Software is to the CPU, what knowledge is to our human brains. The CPU and software work very closely together. Each one by itself is useless. Only when they work properly together can they direct and execute activities in the PC in a productive way.

This chart shows the components we've talked about, grouped together functionally. Arrows show how they show how they interconnect.

The PC and the ATM

What do a PC and an automated teller machine have in common? They are both computer based systems. By explaining the operation of an ATM it may help you see how information flows in a PC based system.

The PC is general purpose. It can run many different types of software that do a wide range of things.

The ATM has all the functional elements of a PC: processor, memory, storage, input, output and software. Like the PC, it can connect to remote computers using communication services in order to access your bank records and determine whether or not to authorize transactions.

The ATM can be thought of as a specialized PC that is designed to do a very limited set of operations. It takes in deposits, dispenses withdrawals and prints out account information.

The ATM software resides in a local or remote storage device and runs on a central processing unit probably a microprocessor or micro controller. It is programmed to sit and wait for you, the user, to tell it what to do.

How do you tell it what to do? With input of course. The basic inputs to the ATM are a keypad, the ATM card reader and the envelope receiver bin used to make deposits.

After the ATM has read your card and you have successfully entered your PIN (Personal Identification Number), which it temporarily stores in memory, you can complete your transaction. Let's say you want to withdraw $100. Using the keypad you select the account and the amount to be debited. The codes for the keys you press go into memory until the processor uses them to determine what action to take. During all this, how do know what the ATM is doing? You know because you are reading a display output that shows you status messages.

The processor in the ATM checks with the remote computers to determine if your bank account is active and if there are sufficient funds to proceed. If so, it slides your money out through the cash dispensing machine door which is another output device. Its then asks you by way of the display if you want to make another transaction. Based on your input it takes the proper action.

If you are done it returns your ATM card, and prints another output device a transaction receipt and closes itself up and waits until someone asks it to do something.

Hopefully you've begun to see what the basic PC functions are and how they work together to perform a useful service for us.

Motherboard

• Motherboards are offered in two basic sizes, ATX (12" wide with varying depths) and ATX mini (8.5" wide, usually with a depth that makes it almost square).

• It is powered from the power supply by means of a 20 pin connector.

• Motherboards with microprocessors on board sell from $160 for an ATX mini with 566Mhz Celeron, up to $850 for an ATX with a 2.0Ghz Pentium 4 installed. There are many options to choose from such as the number and type of expansions slots, the chip set and so on that affect the performance and price.

• Keep in mind that the performance of a PC is not determined solely by the Mhz rating of the microprocessor. The chip set, type of graphics board, speed of the memory bus, amount of memory, access speed of the HDD all affect PC performance.

Memory

Memory is an integrated circuit (chip) that stores information electronically.

DRAM stands for Dynamic Random Access Memory and is the main memory used by the CPU to keep copies of files, programs and other temporary information used by the CPU when it is running.

When you see a computer ad that says '1.2Ghz, 128Mb, 10GB Hard Drive etc,' the 128Mb is the size in mega bytes of the DRAM memory in the PC. A mega byte is 1 million bytes.

Dynamic memory is a type of memory that must be continuously refreshed in order to retain it's contents.

Think of each bit location as if it were a small bucket. The amount of water in the bucket represents the state of the bit stored there. If the bucket is more than half full of water, the bit is a 1. If it is less than half full the bit is a 0. These buckets are leaky (dynamic) due to small holes in the bottom.

DRAM cell leak because the cell structure used is small and inexpensive compared to static (non-leaky) memory. When you charge a cell, setting it to a 1 bit, it immediately begins to lose charge. In a very short time the charge falls below the half way mark and the 1 becomes a 0. Each cell must constantly be refreshed with charge by the CPU or the self- refreshing circuits in newer DRAM devices.

The leaky DRAM cells are less expensive than SRAM cells which don't leak. If SRAMs were used, PC prices would go up noticeably.

Why is the state of one bit so important? Imagine that this bit we've been talking about is a status bit in a payroll program that the CPU uses to determine if you are to be paid this week; 1 means you get paid and 0 means you don't. You can see why a bit changing state when it's not supposed to can have disastrous results!

Random Access means that any location in the memory can be read or written immediately. It's like a CD, which is also random access. When you select a track on a CD it goes to that track and starts playing right away.

Serial Access on the other hand is like an audio or video cassette. You can't access any location you choose to instantly. You might have to rewind or fast forward past lots of stuff to get to the location you want.

What are bits and bytes?

A bit is a binary digit and is the smallest unit of information in a PC. Bits can only have one of two states, either on or off. These two states represent the two values a bit can have, either 1 or 0. A byte is group of 8 bits.

Everything in a computer is stored and calculated using this two value number system, which is called a binary. All storage and calculation operations in a PC are done using binary arithmetic.

The reason there are only two states for a bit is because of the nature of transistors, which are the building blocks for all digital electronic circuits. For technical reasons beyond the scope of this discussion, transistors used in digital circuits can be in only one of two stable states, either fully on or completely off.

In contrast, the number system we use every day is decimal and it has ten states or values. The decimal digits 0,1,2,3,4,5,6,7,8 and 9 represent the ten values a number can have.

SIMMs and DIMMs

Up until recently DRAM memory boards were made in SIMM form, single in-line memory module. Today they are supplied in DIMM form, dual in-line memory module.

Storage

Storage is similar to memory in that both are used to retain information. Storage devices use magnetic or optical means to retain data where memory uses an electronic circuit.

They are non-volatile, which means they do not lose the information they contain when they are powered off. They have greater capacity but are much slower than memory devices.

Floppy Disks, Hard Disks and Tapes all store information magnetically. CDs and DVDs retain information optically. Storage is used to retain important information like programs (software) and data files.

Input Devices

Input devices let you enter information into a PC.

The keyboard, mouse and touch-screen display are examples of input devices.

Input devices get information into the computer by interrupting the CPU from it's main program, in much the same way that you are interrupted in your daily life.

If you are home preparing dinner or watching TV and the door bell rings you have to stop what you are doing, go to the door, see who it is, see what they want, take any appropriate action, say good bye and then go back and pick up where you left off, right?

When you press a key on the keyboard the same thing happens. An interrupt handler (software routine) says 'Hey CPU, stop what you're doing, go over to the keyboard port, read the value of the key the operator just pushed and store this value in memory location X.'

The CPU stops, reads the key, stores the key value in location X, and then goes back to doing what it was doing before the interrupt.This is a simple example. Often an interrupt will cause a PC to run a very complex, time consuming routine to service the interrupt.

The difference is that you probably get interrupted infrequently compared to a PC, unless you have a really busy job, like a switchboard operator, where it could be a few times every minute. A CPU can be interrupted hundreds, even thousands of times per second depending on the environment it is running in.

Output Devices

Output devices are used to provide usable output for us, as well as status about the operation of the PC.

The video display, printer and speaker are examples of output devices.

Video Display

The video display uses data that the CPU puts into a section of memory called video memory. This data is continuously updated and sent to the display at the right rate and in the right order, so that the screen displays images we can read or interpret.

Printer

Most of you have probably used a printer. The PC sends data that you select such as a file or picture to the printer, usually through either a USB or parallel port on the PC.

Speakers

Most PCs come standard with external speakers that plug into the sound card. These speakers play back any audio source that your PC can send to them such as music, voice and status information (beeps), such as those made during start up.

Input/Output (I/O)

There are some ports on the PC that are used to move data out of as well as back into the PC. They are called I/O ports.

• Serial Port - The serial port is an I/O port. It connects to external devices that need to communicate with the PC. Scanners and digital cameras are examples of devices that can connect to the serial port. It is called the serial port because only one bit of information passes across it during each transfer.

• Parallel Port - The parallel port is also an I/O port that is almost always used for output. More often than not a printer connected to it. It's called a parallel port because it moves a byte (8 bits) of data in parallel during each data transfer.

• Universal Serial Bus - The Universal Serial Bus (USB) is a newer higher speed serial I/O port that will eventually replace the serial and parallel ports. It has been appearing in PCs for a relatively short time. Many printers and other external devices are already equipped with USB ports. The USB port on a PC can connect directly to any device with a USB port. It can also connect to a USB Controller which in turn can connect to many devices that have USB ports.

Software

The words software, code and programs are often used interchangeably. They all refers to instruction sequences that run on the hardware of a computer. They can be divided up into two general areas: operating systems and application programs.

Operating Systems

The operating system (OS) is essential code that a PC must have. It is stored on your hard drive. It provides the basic operating platform that brings the PC to a point where it can interpret the keyboard and mouse input and display data and images on the video display. Other programs can't run on a PC until the OS is loaded and running. DOS, Windows 95 and Windows 98 are examples of operating systems.

When an OS like Windows 98 has been loaded and is ready to go, the Windows Desktop appears. All you have to do is point and click on a desktop icon or the Start Button to select an application program you want to use and away you go!

BIOS (Basic Input Output System)

This is essential code that initializes the hardware in your PC and loads the OS. It can loosely be considered to be a part of the OS. When you first turn on your PC it is under the control of BIOS code which is stored in a special memory chip on the mother board.

The BIOS stores configuration information about all the hardware in the PC. The type of hard drive, floppy drive, video display, CD etc. is kept here so that the PC knows how to communicate with these devices. Newer BIOS code has 'auto' modes that can figure out what hardware is attached and how to communicate with it. In older BIOS, if hardware is changed without updating the BIOS the PC may not complete it's boot up cycle, and will just sit there until the new device parameters are loaded into it.

After BIOS copies the OS code from your hard drive into memory, the copy of the OS in memory takes over and finished the initialization process. When it is complete the PC is ready to use application programs.

Application Programs

These are workhorses of code. They are the ones you are probably most familiar with. They run on top of the OS and allow you to use your PC for work or play.

Word, Excel, Frame Maker, Corel Draw and PC games are a just a few examples of the thousands of Application Programs that are available to you.

What happens when your PC
is powered on?

When your PC is powered on a sequence called the bootstrap is run. It occurs in two steps, Power-On Self Test and Operating System Load.

Power-On Self Test (POST) is a series of tests to make certain that necessary is present and properly operating.

1. First the Central Processing Unit (CPU) is reset.

2. The CPU checks itself and the POST program stored in the BIOS memory.

3. Then the CPU begins using the code located in BIOS to check components in the PC.

4. The DRAM is tested by writing and reading back every byte to insure proper operation.

5. The Keyboard is checked for attachment and to see if any key has been pressed.

6. Pushing certain keys during boot up tells the CPU you want to modify the BIOS code. You would want to do this if a new piece of hardware has been added and you need to set up BIOS to talk to it.

7. The Floppy and Hard Drives are checked to make sure they are present.

8. The Mouse is also checked to make sure it is attached.

9. Finally, the test results are compared to the configuration data in the BIOS.

10. Any mismatches causes the POST to fail and an error message appears on the display.

Operating System Load - After the POST is successfully completed the CPU searches Storage devices for special files that indicate the beginning of the OS and then loads it into memory.

1. The sequence in which the storage devices are searched is part of the configuration set-up stored in BIOS.

2. Once the Operating System (OS) is located, the CPU copies what?s called the 'boot record' from the OS into DRAM.

3. Control is then passed to the 'boot record' in DRAM, which then continues loading the rest of the OS.

4. This process continues until the OS load is completed.

5. When the OS load is completed the Desktop appears in the display and waits for you, the user, to tell it what you want it to do.

What is the Internet?

© 2000 Walt Howe
(last updated June 22, 1998)

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The Internet is a vast network that connects many independent networks spanning over 170 countries in the World. It links computers of many different types, sizes, and operating systems, and, of course, the many people of those countries that use the Internet to communicate.

The one thing all these different computers have in common is the use of the Internet Protocol, abbreviated as IP, which allows computers of different types to communicate with each other. You will often see reference to the longer abbreviation, TCP/IP, which stands for Transmission Control Protocol/Internet Protocol. Your own computer uses TCP/IP software to enable it to link to this service.

What can I do on the Internet?

The Internet Protocol makes it possible for you to communicate in various ways, find things that interest you, and exchange information and files. The most common things you can do are:

• Send and receive email with people all over the world. Almost as fast as the telephone, there is never a busy signal, and you never play phone tag.

• Join discussion groups about a common subject with Usenet Newsgroups and email discussion lists.

• Get or exchange software and files with the File Transfer Protocol (FTP)

• Log into and use many computers around the world using telnet. Telnet lets you use the resources on a remote computer such as games, databases, library catalogs, and many more interesting things.

• Connect to thousands of different computers using gopher menu systems, which make navigation from one site to another easy.

• Explore the World Wide Web, which can use all of the above, and adds easy links to other resources and adds multimedia--graphics, sound, and video capabilities.

• Talk by keyboard with Internet Relay Chat (IRC), which lets small groups of users meet in conference to "talk" to each other by typing on their keyboards.

Who Owns the Internet?

No organization, corporation or government owns or runs the Internet. Instead, many people and organizations voluntarily participate in task force groups who meet to develop standards for the many various technical needs of running the Internet. Decisions are made by consensus among all who choose to participate, and every point of view is heard in the long process of hashing out decisions and setting new standards.
The equipment--the computers, the cables, the routers, and so on are owned by government and private organizations and are paid for by taxes and user fees. In the early history of the Internet, the US government paid for many of the development and operating costs through government grants. In recent years, the US government has stepped aside except for the portions that link government organizations and let private enterprise develop the nets.

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What is the World Wide Web?

© 2001 Walt Howe
(last updated 27 April 2001)

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The World Wide Web is one of the protocols that lets you link to many sites on the Internet. The basic unit is the page, such as the page you are now reading. A page can be one or many screens as it displays on your monitor.

Within the page are links to related pages and other web sites. This system of embedding links in the text on a page is called hypertext. The links are distinctive, and vary depending on your browser. With most graphical browsers, links are underlined and appear in a contrasting color.

Text browsers may number the links or show them in bold text to contrast them or in reverse colors when selected. You can select a link in a text browser either by typing the number of the link or by moving the up and down arrow keys to select the link. Once selected, either press Enter or the right arrow to connect to the link.

This page includes several links in contrasting colors or type. These are hypertext links to other pages, and you can switch to the linked page by clicking on or selecting the link. Try it.

You will also see buttons and pictures used for links. With a graphical browser, there will often be a blue or magenta border around the graphic to show you it is a link. If you are using a text-only browser, you won't see the picture, but you will usually see an [image] tag or an alternate name.

The Web was invented by Tim Berners-Lee and others at the European Laboratory for Particle Physics (CERN) in Switzerland. It was originally for text links only, but as it was further developed, multimedia links were added, too. Now, you can see pictures, listen to audio links, and see video links, if your computer and software are set up for them. With the addition of sound and graphics and fast modems to carry the large sound and graphics files, the Web soon became the most popular way of linking to resources on the Internet, replacing gopher, which was invented at the University of Minnesota.

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What can I do on the Internet?

The Internet Protocol makes it possible for you to communicate in various ways, find things that interest you, and exchange information and files. The most common things you can do are:

• Send and receive email with people all over the world. Almost as fast as the telephone, there is never a busy signal, and you never play phone tag.

• Join discussion groups about a common subject with Usenet Newsgroups and email discussion lists.

• Get or exchange software and files with the File Transfer Protocol (FTP)

• Log into and use many computers around the world using telnet. Telnet lets you use the resources on a remote computer such as games, databases, library catalogs, and many more interesting things.

• Connect to thousands of different computers using gopher menu systems, which make navigation from one site to another easy.

• Explore the World Wide Web, which can use all of the above, and adds easy links to other resources and adds multimedia--graphics, sound, and video capabilities.

• Talk by keyboard with Internet Relay Chat (IRC), which lets small groups of users meet in conference to "talk" to each other by typing on their keyboards.

Who Owns the Internet?

No organization, corporation or government owns or runs the Internet. Instead, many people and organizations voluntarily participate in task force groups who meet to develop standards for the many various technical needs of running the Internet. Decisions are made by consensus among all who choose to participate, and every point of view is heard in the long process of hashing out decisions and setting new standards.
The equipment--the computers, the cables, the routers, and so on are owned by government and private organizations and are paid for by taxes and user fees. In the early history of the Internet, the US government paid for many of the development and operating costs through government grants. In recent years, the US government has stepped aside except for the portions that link government organizations and let private enterprise develop the nets.

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Expert Searching

A Guide to Developing Your Search Skills

© 2000 by Walt Howe
(last updated November 27, 2000)

This is a set of guides and tips to searching on the Internet. Taken together, they provide enough information to become a skilled searcher. If you are new to searching, use the Search Engine Guide as your starting point, and come back to the other features listed here as you develop your skills. If you are an experienced searcher, look through all of these features for tips you can use.

1. Search Engine Guide. Links and how-to-do-it instructions for the major search engines and directories. This file is updated regularly.

2. Search Engine Comparison Chart. Comparison of features and capabilities of the major search engines to help you decide which engine or engines to use.

3. Find-It! A Guide to Specialized Searches. There are many search engines devoted to particular types of data, and this is a guide to finding those.

4. Searching the Invisible Web. How to find information that the search engines cannot reach.

5. Search Tip: Find Expert Help. If you can't find the information, locate an expert source to help you.

6. Search Tip: Boolean Searching. Learn to use the full power of Boolean searching to narrow your searches.

7. What to do with 50 Million Hits! How to refine those searches that produce too many results.

8. Finding Broken Links. Broken links are everywhere, even in search engine results. Learn how to track down updated addresses on the nets.

Internet Address Questions

© 2001 Walt Howe
(last updated March 30, 2001)

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Internet Address questions:

· How are Internet addresses formed?

· What is a domain address?

· What is an IP address?

· What is a URL?

· How do I find people's or business' addresses?

Internet Addresses
There are two types of Internet addresses--domain addresses made up of words separated by dots (for example, world.std.com), and IP addresses made up of four numbers separated by dots (for example, 199.0.65.101).

Both types represent computer addresses on the Internet, and for many purposes, either type can be used. Numbered IP addresses represent specific computers on the Internet. Domain addresses may represent a specific computer or may be less specific.

Domain Addresses
Domain name addresses all end with a correct top-level domain. The top-level domains may be any of these:

· com

· edu

· gov

· int

· mil

· net

· org

· a two-letter country code, such as us, uk, or mx. See the country code table.

A complete domain address adds one or more terms to the left of the top-level domain, separated by dots. The top-level domain at the right is the most general; each term to the left is more specific.

The Internet Corporation for Assigned Names and Numbers (ICANN) announced a new series of top level domains to become available for registration in 2001. They are:

· biz

· pro

· museum

· aero

· name

· coop

· info

IP Addresses
IP, or Internet Protocol, addresses consist of four numbers from 0 to 255, separated by dots. The first number is the most general, and each following number is more specific.

A network might be assigned the hypothetical numbers 185.33.27.0 through 185.33.27.255. This would give them 256 numbers to use. A very large network might be given all numbers beginning with, for example, 125.211. This would give that network approximately 65 thousand addresses to use from 125.211.0.0 through 125.211.255.255. More commonly, a network will be assigned a portion of the range appropriate to its size.

Internet Mail Questions

© 2001 Walt Howe
(last updated 27 April 2001)

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Mail questions:

1. How do I set up my e-mail software to send and receive mail?

2. How do I address mail?

3. How can I mail text files?

4. How can I mail binary files?

5. How can I auto-forward mail to another address?

6. How can I find someone's e-mail address?

7. How can I create a distribution list to send a message to a lot of people?

8. For Delphi members: How do I change my e-mail address?

9. For Delphi members: How do I send e-mail to a member when I don't know the person's e-mail address?

1. How do I setup my e-mail software to send and receive mail?
   If you want to receive and send mail from Delphi (or other ISPs) using mail software like Outlook, Eudora, or Pegasus or the mail capability of Netscape or MSIE, you need to enter the correct addresses, your username, and your password. In general, the address to receive mail from is pop.yourdomain.com. Some software will have you add your username to that address, so that you list username@pop.yourdomain.com. To send mail, generally use the form smtp.yourdomain.com. There are many variations to these addresses, so check with your e-mail provider for exact addressing.

The pop and smtp prefixes are common, and to collect and send mail from other addresses, you often use the same form. If in doubt, check with your provider.

Recent versions of Outlook Express, Eudora Pro and Pegasus allow you to set up more than one receive address, so you can collect mail from different accounts. Most providers will let you collect mail from a remote address, but not all do.

2. How do I address mail?
   To send mail, you must know the correct address and fill it in at the To: prompt. Simple Internet mail addresses consist of a Username, an @ symbol, and the address, which will consist of at least two words, separated by periods. For example, this is a correctly formatted address:

3.    To:  jsmith@delphiforums.com

There is never more than one @ symbol in an address. Rarely, you will encounter an alternate form of address that uses exclamation points (called bang addresses) instead of an @ symbol or one in which there are several levels of addresses in which one or more % symbols act as secondary @ functions.

All addresses (other than those with exclamation points) must end with a correct domain. The domains may be any of these:

• com

• edu

• gov

• int

• mil

• net

• org

• a two-letter country code.

A recent international meeting approved the use of new top-level domain names. Implementation dates remain to be worked out.

4. How can I mail text files?
   Unless you are sure that your addressee can receive separate files, it is best to include a text file as the text of the message itself. In Eudora, you can do this by clicking on the Attach file icon (the one to the right of the left and right arrows) and inserting the filename of the file to be attached, as prompted. Before mailing the attachment, select Special/Settings/ Attachments and click on the box labelled "Put text attachments in body of message."

5. How can I mail binary files?
   Not all addresses can receive binaryfiles by e-mail. It requires a compatible mailer. If you are not sure, ask your addressee if their mailer supports MIME. If so, using Eudora, you can attach the binary file by clicking on the Attach file icon (the one to the right of the left and right arrows) and inserting the filename of the file to be attached, as prompted. Before mailing the attachment, select Special/Settings/ Attachments and make sure the MIME button is checked.

If your addressee cannot accept MIME, you can still check uuencode or binhex, and the file will be encoded into either of these two text forms. Your addressee may need to decode them separately, but decoders for uuencode and binhex are very common for all systems. Binhex is primarily used by Macintosh computers.

If your mail software will not handle the automatic encoding, you can use appropriate software such as uuencode or WinCode for PCs, or binhex or stuffit for Macs to do the job offline, and then send the file as a text attachment.

6. How can I forward mail to another address?
   Most mail providers give you a way to forward e-mail automatically to another address. Check your provider's documentation for the exact methods.

Unix shell systems usually allow you to create a file named .forward (dot forward) in your workspace, which is a text file consisting of the forwarding address, such as username@delphiforums.com

Whichever system you use, it is a good idea to test it with a test message after you set the forwarding.

7. How do I find someone's e-mail address? Most online services will not give out personal information like e-mail addreses. On the other hand, some people register them and make them widely available. Other e-mail addresses are collected from usage. See our Find People and Businesses page for some of the places where you can try to look someone up.