Tech Terms C-D

Cache
When you download a web page, the data is "cached," meaning it is temporarily stored on your computer. The next time you want that page, instead of requesting the file from the web server, your web browser just accesses it from the cache, so the page loads quickly. The one downside to this is that if the website you have cached is often updated you may miss the latest "version". If this occurs you can use the refresh button on your browser.

CAD
Computer-Aided Design (CAD) is a type of software that allows users to create 2D and 3D design and modelling. CAD is used by architects, engineers, artists and other professionals to create precise technical drawings.

Chat Room
An electronic space, typically a website or a section of an ISP where people can go to communicate online in real time. Chat Rooms are generally devoted to a particular interest or topic.

Chips
A "chip" is the microprocessor that performs many functions and calculations that make your computer run. A chip is also referred to as the CPU or the processor.

Cloud Computing
Cloud computing refers to the storing and accessing of data and programs over the Internet instead of another type of hard drive. Examples of Cloud services include iCloud, Google Cloud, Dropbox etc.

Compression
Compression is the reduction of the size of a file. A compression program will save a file differently so that it takes up less memory and can be downloaded or sent over the Internet more quickly.

Content
Content refers to the text and information included in a website, as opposed to the design and structure of the site.

Cookie
A piece of code or data created by a web server that is stored on a user's computer. It is used to keep track of the user's patterns and preferences.

CPU
The Central Processing Unit (CPU) is the brains behind your computer. The CPU is responsible for performing calculations and tasks that make programs work. The higher the speed of a CPU, the faster the CPU undertakes the calculations and tasks.

Cybercrime
Cybercrime is a term used to define any type of illegal activity that uses a computer as its main device to perform the activity. There are thousands of types of cybercrime, including network intrusions, identity theft and the spreading of computer viruses.

Cybersecurity
Cybersecurity is the process of protecting your computer, device or network from cybercrime. This involves the employment of certain technologies, processes and practices that help to prevent unintended and unauthorised access, change and damage.

Database
A database is a set of information that is structured primarily to allow calculations and analysis to be undertaken. Microsoft Access is the main lower level database used.

Defragment
A fragmented file or folder is split up into many pieces and scattered over the storage capacity on your hard drive. This means that it takes a lot longer to load and process files. A regular defragment will ensure that files are stored more logically and will help speed up processes.

Device Driver
A device driver is a small program that allows a peripheral device such as a printer or scanner to connect to your PC.

Disk Drive
A round object that you use to store digital information. Floppy Disks (FDD) are usually allocated the A: Drive and the Hard Disk is usually allocated the C:\ Drive (HDD) on your PC.

Domain
A domain is a set of computers on a network that are managed as a unit. On the Internet, a domain is defined by an IP or URL address. The way users encounter a domain is through the domain name.

Download
Downloading is the method by which users access and save or "pull down" software or other files to their own computers from a remote computer via the Internet.

DV
DV stands for digital video.

How the PC Works...(part 2)

To see how a PC works, let's start with the pieces that come together to make up the machine. The following are the components common to PCs in the order they're typically assembled:

Case -- If you're using a laptop, the computer case includes keyboard and screen. For desktop PCs, the case is typically some type of box with lights, vents, and places for attaching cables. The size of the case can vary from small tabletop units to tall towers. A larger case doesn't always imply a more powerful computer; it's what's inside that counts. PC builders design or select a case based on the type of motherboard that should fit inside.

Motherboard -- The primary circuit board inside your PC is its motherboard. All components, inside and out, connect through the motherboard in some way. The other components listed on this page are removable and, thus, replaceable without replacing the motherboard. Several important components, though, are attached directly to the motherboard. These include the complementary metal-oxide semiconductor (CMOS), which stores some information, such as the system clock, when the computer is powered down. Motherboards come in different sizes and standards, the most common as of this writing being ATX and MicroATX. From there, motherboards vary by the type of removable components they're designed to handle internally and what ports are available for attaching external devices.

Power supply -- Other than its CMOS, which is powered by a replaceable CMOS battery on the motherboard, every component in your PC relies on its power supply. The power supply connects to some type of power source, whether that's a battery in the case of mobile computers, or a power outlet in the case of desktop PCs. In a desktop PC, you can see the power supply mounted inside the case with a power cable connection on the outside and a handful of attached cables inside. Some of these cables connect directly to the motherboard while others connect to other components like drives and fans.

Central processing unit (CPU) -- The CPU, often just called the processor, is the component that contains the microprocessor. That microprocessor is the heart of all the PC's operations, and the performance of both hardware and software rely on the processor's performance. Intel and AMD are the largest CPU manufacturers for PCs, though you'll find others on the market, too. The two common CPU architectures are 32-bit and 64-bit, and you'll find that certain software relies on this architecture distinction.

Random-access memory (RAM) -- Even the fastest processor needs a buffer to store information while it's being processed. The RAM is to the CPU as a countertop is to a cook: It serves as the place where the ingredients and tools you're working with wait until you need to pick up and use them. Both a fast CPU and an ample amount of RAM are necessary for a speedy PC. Each PC has a maximum amount of RAM it can handle, and slots on the motherboard indicate the type of RAM the PC requires.

Drives -- A drive is a device intended to store data when it's not in use. A hard drive or solid state drive stores a PC's operating system and software, which we'll look at more closely later. This category also includes optical drives such as those used for reading and writing CD, DVD and Blu-ray media. A drive connects to the motherboard based on the type of drive controller technology it uses, including the older IDE standard and the newer SATA standard.

Cooling devices -- The more your computer processes, the more heat it generates. The CPU and other components can handle a certain amount of heat. However, if a PC isn't cooled properly, it can overheat, causing costly damage to its components and circuitry. Fans are the most common device used to cool a PC. In addition, the CPU is covered by a metallic block called a heat sink, which draws heat away from the CPU. Some serious computer users, such as gamers, sometimes have more expensive heat management solutions, like a water-cooled system, designed to deal with more intense cooling demands.

Cables -- All the components we've mentioned so far are connected by some combination of cables. These cables are designed to carry data, power or both. PCs should be constructed so that the cables fold neatly within the case and do not block air flow throughout it.

A PC is typically much more than these core components. Next, we'll look at the ports and peripherals that let you interact with the computer and how you can add even more components using expansion slots.

Ports, Peripherals and Expansion Slots
The core components we've looked at so far make up a PC's central processing power. A PC needs additional components, though, for interacting with human users and other computers. The following are the PC parts that make this happen:

Graphics components -- While some motherboards have on-board graphics, others include what's called an expansion slot, where you can slide in a separate video card. In both cases, the video components in a PC process some of the complex graphics data going to the screen, taking some of the load off your CPU. A motherboard accepts video cards based on a specific interface, such as the older AGP standard or one of the newer PCI standards.

Ports -- The word port is often used to describe a place on the outside of your PC where you can plug in a cable. Describe a port by its use, such as a USB port or an Ethernet port. (Note that the word port is also used to describe a software connection when two pieces of hardware try to communicate.) Many ports are affixed directly to the motherboard. Some of the ports you'll find on a PC include the following:

• USB ports
• network ports, typically Ethernet and FireWire
• video ports, typically some combination of VGA, DVI, RCA/component, S-Video and HDMI
• audio ports, typically some combination mini analog audio jacks or RCA
• legacy ports, or ports that follow old standards which are rarely used in modern computers, such as parallel printer ports and PS2 ports for a keyboard and mouse

Peripherals -- Any piece of hardware that isn't mounted inside a PC's case is called a peripheral. This includes your basic input and output devices: monitors, keyboards and mice. It also includes printers, speakers, headphones, microphones, webcams and USB flash drives. Anything you can plug in to a port on the PC is one of the PC's peripherals. The essential peripherals (such as monitors) aren't necessary on laptops, which have them built in instead.

Expansion slots -- On occasion, you'll want to add components to a PC that don't have a designated slot somewhere on the motherboard. That's why the motherboard will include a series of expansion slots. The removable components designed to fit into expansion slots are called cards, probably because of their flat, card-like structure. Using expansion slots, you can add extra video cards, network cards, printer ports, TV receivers and many other custom additions. The card must match the expansion slot type, whether it's the legacy ISA/EISA type or the more common PCI, PCI-X or PCI Express types.

Tech Terms A-B

ABI/Inform
A database of articles in more than 800 business-related periodicals and specialty publications since 1986.


Access Provider
The company that provides you with Internet access and, in some cases, an online account on their computer system.


Acoustic Coupler 
A type of modem which converts digital signals into sound for transmission through telephone lines, and performs the reverse operation when receiving such signals. Acoustic couplers generally have cups for the telephone handset.


Active Window 
The top or front window in a multiple window environment.


A/D Converter 
A device used to convert analog data to digital data. Analog data is continuously variable, while digital data contains discrete steps.


Additive Primaries
Red, green, and blue are the primary colors of light from which all other colors can be made.


Address Resolution 
Conversion of an IP Address to the corresponding low-level physical address.


AIX 
Advanced Interactive Executive - IBM's version of Unix.


Aliasing
Visibly jagged steps along angled or object edges, due to sharp tonal contrasts between pixels.


Analog
Continuously variable signals or data.


Anonymous Login Convention (FTP)
Standard username (anonymous) and password (guest) which allows login within FTP for the purpose of retrieving an unprotected file.


ANSI 
American National Standards Institute. This organization is responsible for approving U.S. standards in many areas, including computers and communications. Standards approved by this organization are often called ANSI standards (e.g., ANSI C is the version of the C language approved by ANSI).


Application 
Software that lets users do relatively complex tasks, as well as create and modify documents. Common application types include word processors, spreadsheets, database managers, and presentation graphics programs.


ARA 
AppleTalk Remote Access. A protocol (and product) that provides system-level support for dial-in (modem) connections to an AppleTalk network. With ARA, you can call your desktop Mac from a PowerBook and remotely access all the available services - files, printers, servers, e-mail, etc.


Archie 
An information system offering an electronic directory service for locating information in the Internet that is automatically updated. The best known use of archie is for scanning a database of the contents of more than 1000 Anonymous FTP sites around the world with more than 2,100,000 file names.


ARP 
Address Resolution Protocol. Used to dynamically discover the low-level physical network hardware address that corresponds to the high level IP Address for a given host, for instance. ARP is limited to physical network systems that support broadcast packets that can be heard by all hosts on the network. A pioneering long-haul network funded by ARPA, an agency of the U.S. Department of Defense responsible for the development of new technology for the military. It served as the basis for early networking research   as well as a central backbone during the development of the Internet. The ARPANET consisted of individual packet switching computers interconnected by leased lines.


ASCII
American (National) Standard Code for Information Interchange. A standard character-to-number               encoding widely used in the computer industry.


Associate 
 Linking a document with the program that created it so that both can be opened with a single command.


AV
Audio-Visual. AV Macintosh models have video-capture hardware and have sophisticated sound (and video) recording capabilities.


AU sounds
A type of audio format used in the World Wide Web.

B

Byte. One character of information, usually eight bits wide.

Backbone

Network used to interconnect several networks together.

Backup file 

In Windows 95, a compressed version of the original file and its locations created by Backup.

Bandwidth 

The capacity of the transmission medium stated in bits per second or as a frequency. The bandwidth of optical fiber is in the gigabit or billion bits per second range, while ethernet coaxial cable is in the megabit or million bits per second range.

Baseband System

A baseband system transmits signals without converting them to another frequency and is characterized by its support of one frequency of signals. Ethernet-based networks inside campus buildings are transmitted via baseband coaxial cable, with ethernet being the only service supported by the coaxial cable.

BAT 

Filename extension for a batch file.

Batch Scanning

Sequential scanning of multiple originals using previously defined, unique settings for each.

Baud 

A unit of measurement that denotes the number of bits that can be transmitted per second. For example, if a modem is rated at 9600 baud it is capable of transmitting data at a rate of 9600 bits per second. The term was derived from the name of J.M.E. Baudot, a French pioneer in the field of printing telegraphy.

BBS 

Bulletin Board Service. A non commercial dial-up service usually run by a user group or software company. By dialing up a BBS with your modem, you can exchange messages with other users, and upload or download software.

BGI 

Binary Gateway Interface. Provides a method of running a program from a Web server. Similar to a Common Gateway Interface (CGI). The BGI uses a binary DLL which is loaded into memory when the server starts. While more efficient han a CGI, the BGI must be compiled and is not easily portable to other environments.

Bilevel

A type of image containing only black and white pixels.

Binary 

A numbering system with only two values: 0 (zero) and 1 (one).

Binary File 

A file that contains more than plain text (i.e., photos, sounds, spreadsheet, etc.) In contrast to an ASCII file which only contains plain text.

Binary Number System

A counting system used in computers consisting of only 1's and 0's (zeros).

BinHex 

A file conversion format that converts binary files to ASCII test files.

BIOS 

Basic Input-Output System. Part of the computer's operating system that is built into the machine, rather than read from a disk drive at startup.

bit 

A unit of measurement that represents one figure or character of data. A bit is the smallest unit of storage in a computer. Since computers actually read 0s and 1s, each is measured as a bit. The letter A consists of 8 bits which amounts to one byte. Bits are often used to measure the capability of a microprocessor to process data, such as 16-bit or 32-bit.

Bit Depth

The number of bits used to represent each pixel in an image, determining its color or tonal range.

Bit-map 

Generally used to describe an illustration or font file as being created by a predefined number of pixels. Also see Object-oriented.

BITNET 

An academic computer network that provides interactive electronic mail and file transfer services, using a store-and-forward protocol, based on IBM Network Job Entry protocols. BITNET-II encapsulates the BITNET protocol within IP packets and depends on the Internet to route them. There are three main constituents of the network: BITNET in the United States and Mexico, NETNORTH in Canada, and EARN in Europe. There are also AsiaNet, in Japan, and connections in South America. See CREN.

Black Point

A movable reference point that defines the darkest area in an image, causing all other areas to be adjusted accordingly.

Booting 

Starting up a computer via the power switch, which loads the system software into memory. Restarting the computer via a keystroke combination is called rebooting or a warm boot.

Bridge 

A dedicated computer used to connect two different networks. It uses data link layer address (i.e., ethernet physical addresses) to determine if packets should be passed between the networks.

Broadband System 

A broadband system is capable of transmitting many different signals at the same time without interfering with one another. For local area networks, a broadband system is one that handles multiple channels of local area network signals distributed over Cable Television (CATV) hardware.

Broadcast 

A packet whose special address results in its being heard by all hosts on a computer network.

Browser 

A program that enables you to access information on the Internet through the World Wide Web.

bps 

Bits Per Second is the unit used for measuring line speed, the number of information units transmitted per second.

BSD 

Berkeley Software Distribution. Implementation of the UNIX operating system and its utilities developed and distributed by the University of California at Berkeley. BSD is usually preceded by the version number of the distribution, e.g., 4.3 BSD is version 4.3 of the Berkeley UNIX distribution. Many Internet hosts run BSD software, and it is the ancestor of many commercial UNIX implementations.

Bug 

A mistake, or unexpected occurrence, in a piece of software or in a piece of hardware.

Byte 

The amount of memory needed to store one character such as a letter or a number. Equal to 8 bits of digital information. The standard measurement unit of a file size.

History of Computers

Definition of a Computer - before 1935, a computer was a person who performed arithmetic calculations. Between 1935 and 1945 the definition referred to a machine, rather than a person. The modern machine definition is based on von Neumann's concepts: a device that accepts input, processes data, stores data, and produces output.

We have gone from the vacuum tube to the transistor, to the microchip. Then the microchip started talking to the modem. Now we exchange text, sound, photos and movies in a digital environment.

Computing milestones and machine evolution:
• 14th C. - Abacus - an instrument for performing calculations by sliding counters along rods or in grooves
• 17th C. - Slide rule -  a manual device used for calculation that consists in its simple form of a ruler and a movable middle piece which are graduated with similar logarithmic scales
• 1642 - Pascaline--a mechanical calculator built by Blaise Pascal, a 17th century mathematician, for whom the Pascal computer programming language was named .
• 1804 - Jacquard loom - a loom programmed with punched cards invented by Joseph Marie Jacquard
• ca 1850 - Difference Engine , Analytical Engine - Charles Babbage and Ada Byron. Babbage's description, in 1837, of the Analytical Engine, a hand cranked, mechanical digital computer anticipated virtually every aspect of present-day computers. It wasn't until over a 100  years later that another all purpose computer was conceived. Sketch of the Engine and notes by Ada Byron King, Countess of  Lovelace.
• 1939 -1942 - Atanasoff Berry Computer -  built at Iowa State by Prof. John V. Atanasoff and graduate student Clifford Berry.  Represented several "firsts" in computing, including a binary system of of arithmetic, parallel processing, regenerative memory, separation of memory and computing functions, and more. Weighed 750 lbs. and had a memory storage of 3,000 bits (0.4K).  Recorded numbers by scorching marks into cards as it worked through a problem. See diagram.
• 1940s - Colossus - a vacuum tube computing machine which broke Hitler's codes during WW II. It was instrumental in helping Turing break the German's codes during WW II to turn the tide of the war.  In the summer of 1939, a small group of scholars became codebreakers, working at Bletchley Part in England.  This group of pioneering codebreakers helped shorten the war and changed the course of history.  See the the Bletchley Park Web site and its history.  See more information on Codes and Ciphers in the Second World War at Tony Sales' site.
• 1946 - ENIAC - World's first electronic, large scale, general-purpose computer, built by Mauchly and Eckert, and activated at the University of Pennsylvania in 1946. ENIAC recreated on a modern computer chip.  See an explanation of ENIAC on a Chip by the Moore School of Electrical Engineering, University of Pennsylvania. The ENIAC is a 30 ton machine that measured 50 x 30 feet. It contained 19,000 vacuum tubes, 6000 switches, and could add 5,000 numbers in a second, a remarkable accomplishment at the time. A reprogrammable machine, the ENIAC performed initial calculations for the H-bomb.  It was also used to prepare artillery shell trajectory tables and perform other military and scientific calculations. Since there was no software to reprogram the computer, people had to rewire it to get it to perform different functions.  The human programmers had to read wiring diagrams and know what each switch did. J. Presper Eckert, Jr. and John W. Mauchly drew on Alansoff's work to create the ENIAC, the Electronic Numerical Integrator and Computer.
• 1951-1959 - vacuum tube based technology. Vacuum Tubes are electronic devices, consisting of a glass or steel vacuum envelope and two or more electrodes between which electrons can move freely. First commercial computers used vacuum tubes: Univac, IBM 701.
• 1950s -1960s - UNIVAC - "punch card technology" The first commercially successful computer, introduced in 1951 by Remington Rand. Over 40 systems were sold. Its memory was made of mercury filled acoustic delay lines that held 1,000 12 digit numbers. It used magnetic tapes that stored 1MB of data at a density of 128 cpi. UNIVAC became synonymous with computer (for a while). See UNIVAC photo . See UNIVAC flow chart
• 1960 IBM 1620 - See photos at The Computer History Museum.
• 1960-1968 - transistor based technology. The transistor, invented in 1948, by Dr. John Bardeen, Dr. Walter Brattain, and Dr. William Shockley. It almost completely replaced the vacuum tube because of its reduced cost, weight, and power consumption and its higher reliability. The transistor is made to alter its state from a starting condition of conductivity (switched 'on', full current flow) to a final condition of insulation (switched 'off', no current flow).
• 1969 - The Internet, originally the ARPAnet (Advanced Research Projects Agency network), began as a military computer network.
• 1969-1977 - integrated circuits (IC) based technology.  The first integrated circuit was demonstrated by Texas Instruments inventor, Jack Kilby, in 1958. It was 7/16" wide and contained two transistors. Examples of early integrated circuit technology: Intel 4004, Dec pdp 8, CRAY 1 (1976) - a 75MHz, 64-bit machine with a peak speed of 160 megaflops, (One million floating point operations per second) the world's fastest processor at that time. Now circuits may contain hundreds of thousands of transistors on a small piece of material, which revolutionized computing.  Here is a diagram of a modern integrated circuit, known as a chip.
• 1976 - CRAY 1 - The world's first electronic digital computer, developed in 1946. A 75MHz, 64-bit machine with a peak speed of 160 megaflops, (one million floating point operations per second) the world's fastest processor at that time.
• 1976 - Apples/MACs - The Apple was designed by Steve Wozniak and Steve Jobs. Apple was the first to have a "windows" type graphical interface and the computer mouse. Like modern computers, early Apples had a peripheral keyboard and mouse, and had a floppy drive that held 3.5" disks.The Macintosh replaced the Apple. See a picture of the The Apple III (1980 - 1985).
• 1978 to 1986 - large scale integration (LSI); Alto - early workstation with mouse; Apple, designed by Steve Wozniak and Steve Jobs. Apple was the first to have a "windows" type graphical interface and the computer mouse. See Apple/MACs evolution over time. The PC and clone market begins to expand.  This begins first mass market of desktop computers.
• 1986 to today - the age of the networked computing, the Internet, and the WWW.
• 1990 - Tim Berners-Lee invented the networked hypertext system called the World Wide Web.
• 1992 - Bill Gates' Microsoft Corp. released Windows 3.1, an operating system that made IBM and IBM-compatible PCs more user-friendly by integrating a graphical user interface into the software. In replacing the old Windows command-line system, however, Microsoft created a program similar to the Macintosh operating system. Apple sued for copyright infringement, but Microsoft prevailed.  Windows 3.1 went to Win 95, then Win 98, now Windows XP .... (There are other OSs, of course, but Windows is the dominant OS today. MACs, by Apple, still have a faithful following.  Linux has a faithful following.
• 1995 - large commercial Internet service providers (ISPs), such as MCI, Sprint , AOL and UUNET, began offering service to large number of customers.
• 1996 - Personal Digital Assistants (such as the Palm Pilot became available to consumers.  They can do numeric calculations, play games and music and download information from the Internet.

Safety and Tools

When repairing computers, like anything else, safety is always first. There are few tricks and tools of the trade to keep you safe and help with the repair of any computer. This section will start with things to look out for to keep you safe and end with the tools of the trade to help you complete your task.

Electrostatic Discharge (ESD)

Electrostatic discharge (ESD) is the release of static electricity when two objects come into contact. Familiar examples of ESD include the shock we receive when we walk across a carpet and touch a metal doorknob and the static electricity we feel after drying clothes in a clothes dryer. A more extreme example of ESD is a lightening bolt. While most ESD events are harmless, it can be an expensive problem in many industrial environments.

ESD first requires a build-up of an electrostatic charge. This occurs when two different materials rub together. One of the materials becomes positively charged; the other becomes negatively charged. The positively-charged material now has an electrostatic charge. When that charge comes into contact with the right material, it is transferred and we have an ESD event. The heat from the ESD event is extremely hot, although we do not feel it when we are shocked. However, when the charge is released onto an electronic device such as an expansion card , the intense heat from the charge can melt or vaporize the tiny parts in the card causing the device to fail. Sometimes an ESD event can damage a device, but it continues to function. This is a called a latent defect, which is hard to detect and significantly shortens the life of the device

Many electronic devices are susceptible to low voltage ESD events. For example, hard drive components are sensitive to only 10 volts. For this reason, manufacturers of electronic devices incorporate measures to prevent ESD events throughout the manufacturing, testing, shipping, and handling processes. For example, an employee may wear a wrist strap when working with devices or may wear ESD control footwear and work on an ESD floor mat that causes the electrostatic charge to go into the ground instead of into the device. Sensitive devices can be packaged with materials that shield the product from a charge.

Anti-static Tools

Anti-static tools are just as they sound. They are tools with the sole purpose of expelling static from computer, you, and the computers parts. Some of these tools include wristbands, mats, and bags.

Anti-static Wrist Strap

An anti-static wrist strap is a key piece of safety gear that helps to prevent the buildup of static electricity near sensitive electronics or other projects where static charge could damage electronics or cause safety issues. The wrist strap is often used with an anti-static mat or other type of work space covering. Special, highly conductive threads on the wrist strap lead to a ground conductor in order to discharge static electricity safely.

While users often take advantage of an anti-static wrist strap to protect items like circuit boards during construction, testing or other activities, some of these devices also qualify as personal protective equipment (PPE), where grounded anti-static devices can help protect wearers in higher voltage situations. Other common situations for using anti-static tools may be based on specific protocols. For example, when an ESD wrist strap is used to protect a PC, the ground is often attached to the computer chassis.

Manufacturers will usually provide items like a wrist strap devices in accordance with specific industry standards. Many of these items have been evaluated by Underwriter Laboratories, a prime tester of electronics handling equipment. Most products will also be marked according to maximum voltage.

Anti-static Mat

In anti-static floor mat or ground mat is an anti-static device that safeguards an individual or piece of equipment like a PC from an electrostatic discharge (ESD). Computer components that are sensitive to static electricity or ESD are motherboards, CPUs, expansion cards and memory devices.

Anti-static mats are used under keyboards or mice and may also be placed on or under other equipment. They are particularly useful when working on computer components. Once an anti-static mat is grounded, it is important not to lift the component off the mat because it will be susceptible to ESD.

An anti-static mat is designed to help lessen the effects of an electrostatic discharge (ESD) on an individual or static-sensitive component. It also assists in preventing explosions and fires when working with flammable material found in certain gases and liquids.

An anti-static mat contains a conductive material that accumulates static. Because it collects electricity, it needs to be grounded or earthed. This is accomplished by plugging it into a grounded electrical outlet.

Devices that are sensitive to an electrostatic discharge are mostly electrical components. Common modules on a PC that are electrostatic-sensitive are:
• Complementary metal-oxide-semiconductor (CMOS) chips, found in CPUs and graphic cards
• Transistor-transistor logic (TTL) chips
• Metal-oxide-semiconductor field-effect transistors (MOSFET)
• Laser diodes (LD)
• High precision resistors
• Blue-light-emitting diodes (LEDs)
Aside from an anti-static mat, there are other electrostatic devices, including anti-static straps, anti-static bags, anti-static agents and anti-static garments.

Electromagnetic Interference (EMI)

EMI (electromagnetic interference) is the disruption of operation of an electronic device when it is in the vicinity of an electromagnetic field (EM field) in the radio frequency (RF) spectrum that is caused by another electronic device.

The internal circuits of personal computers generate EM fields in the RF range. Also, cathode ray tube (CRT) displays generate EM energy over a wide band of frequencies. These emissions can interfere with the performance of sensitive wireless receivers nearby. If you have a wireless receiver of any kind and use it at the same time as you operate your personal computer, you will probably hear RF noise in the receiver that originates in the PC system.

Moderate- or high-powered wireless transmitters can produce EM fields strong enough to upset the operation of electronic equipment nearby. If you live near a broadcast station or in the downtown area of a large city, you have probably experienced EMI from radio or television transmitters. Cordless telephones, home entertainment systems, computers, and certain medical devices can fail to work properly in the presence of strong RF fields.

Problems with EMI can be minimized by ensuring that all electronic equipment is operated with a good electrical ground system. In addition, cords and cables connecting the peripherals in an electronic or computer system should, if possible, be shielded to keep unwanted RF energy from entering or leaving. Specialized components such as line filters, capacitors, and inductors can be installed in power cords and interconnecting cables to reduce the EMI susceptibility of some systems. Before performing any modifications to equipment, contact the manufacturer for technical assistance. This is especially important if modifications might void an existing warranty, and it is imperative with medical devices of any kind.

What can computers do?

Too often people buy computers and do not know how to use them to their full potential. In the workplace, many people use computers to keep records, analyze data, do research, and manage projects. At home, you can use computers to find information, store pictures and music, track finances, play games, and communicate with others—and those are just a few of the possibilities.

You can also use your computer to connect to the Internet, a network that links computers around the world. Internet access is available for a monthly fee in most urban areas, and increasingly, in less populated areas. With Internet access, you can communicate with people all over the world and find a vast amount of information. Below is a list of numerous operations a computer can do:

1.      Connecting to the internet – This is one of the most popular thing to do on a computer.

2.      Using your word processor – Below are some example of what a word processor can do:

a.       Write your own document, report, or even your own book.

b.      Help check for spelling and grammar errors in your text.

c.       View other documents, manuals, or other word processor files.

d.      Link the word processor to an external source, such as Outlook, Excel, or other source, and create your own labels.

e.       Create flyers, handouts, or other pages with graphics and pictures.

3.      Using spreadsheets – Most computers today have programs where you can use spreadsheets. Below are some examples:

a.       Write your own document, report, or even your own book.

b.      Help check for spelling and grammar errors in your text.

c.       View other documents, manuals, or other word processor files.

d.      Link the word processor to an external source, such as Outlook, Excel, or other source, and create your own labels.

e.       Create flyers, handouts, or other pages with graphics and pictures.

4.      Broaden your knowledge - 
a.       Dictionary, Thesaurus, Encyclopedia - There are hundreds of available software versions of dictionaries, thesauruses, and Encyclopedias that you can either use to browse and learn more about everything or as a reference to look up information.

b.      Geographical or Map software - There are several companies that make very sophisticated geographical and map programs that enable users to learn more about the world or a specific location, lookup directions, find a local store, etc. See our map information page for a listing of free online map services.

c.       Language software - There are numerous programs available that help users learn different languages and even translate text from one language into another.

5.      Play Games - 

a.       Children learning games - There are hundreds of games for young children (12 and younger) that are not only enjoyable to play but often also educational.

b.      Teenager and older games - By far the most popular games, the games that are often played for entertainment value.

c.       Learning games - There are numerous learning games for all people and all age groups. For example, many flight simulators are available that help users learn to fly, and at the same time are really enjoyable.

d.      Online games - Users who have access to the Internet also have access to millions of free online games sites like http://games.yahoo.com and others have hundreds of games you can play against other Internet users from around the world.

6.      Listen to music, create your own music or music CDs - With the advent of MP3 files and the increased popularity of sharing music legally and illegally, computers have become a great way of getting new music and listening to your favorite artists. Below is some general information about how you can listen to music on your computer.

a.       Install a sound player - To listen to music on your computer you will first need a player. New versions of Windows come with Windows Media Player and there are several programs such as Winamp that you can download freely from the Internet that allow you to listen to the music files.

b.      Download or copy sound file - Each song, and sometimes a whole CD, is contained in a sound file, often an MP3 file. These files can be downloaded from various sites on the Internet that will charge you a small fee, or if public domain allow you to download the song for free. Keep in mind that unless the song is public domain (something you would not buy at a store), downloading the song for free is considered illegal, even though many sites have this ability.

You can also rip or copy songs from CDs you already own and create your own MP3 files. A free and excellent program we suggest for creating songs from your CD is CDex.

Once the songs have been copied to your computer, you can listen to them in the player any time. Not only is this easier than inserting the CD each time you want to play a song, this also allows you to have all the songs you enjoy listening to on your computer.

c.       Internet Radio - Users with Internet access can also listen to millions of online radio stations. Both players we mentioned above, as well as most new players, support the ability to listen to streaming content.

7.      Look at pictures, scan pictures, import pictures, and create your own pictures - Computers are capable of storing billions of pictures and can have access to almost any picture imaginable. You can also move your own personal pictures onto your computer from your digital camera, scanners, or by using other computer peripherals.

After moving your pictures onto your computer, you change almost anything about them by editing them in an image editor. Examples are improving an image's appearance, as well as cropping or copying it. After your done editing, you can move images them into another program and create personal slide shows or burn a CD with pictures on it.

8.      Use your computer to control appliances and lights in your house - With the proper software and hardware your computer can automate different appliances, lights, sprinklers, and even your thermostat.

9.      Keep personal information and contacts stored electronically and share it with other devices - Personal Digital Assistants (PDAs) and cell phones capable of keeping and storing contacts, to-do lists, calendars, etc have become widely used. Keep your contacts on your computer and synchronized with each other to have access to all your contacts on both devices as well as a backup.

10.  Watch videos, create your own movies, or watch TV - Users can now watch short video clips and movies on their computer as well as create their own. Below are some of the different methods of watching and creating your own videos and movies.

a.       DVD movies - Many of the new computers today come with their own DVD drive, which means you can watch any of your DVD movies on your computer. Users who do not have their own DVD player for their TV can also connect their computer to their TV and watch the DVD movie on their TV (may require additional hardware).

b.      Short videos - There are millions of short videos available through the Internet and included with software programs. These are videos that are often no longer than 10 minutes and that are often homemade videos or videos that accompany the software program they were included on.

c.       Create your own movies - Today, there are numerous software programs available to help you create and edit movies. Users with the proper hardware and connections can also connect external sources to their computer to copy movies. For example, a user could connect his or her camcorder to the computer and copy their personal movies from it.

d.      Watch TV - With a TV tuner card in the computer you can watch TV on your computer. This enables people who enjoy both TV and computer to enjoy them at the same time.

Types of Computers

Computers range in size and capability. At one end of the scale are supercomputers, very large computers with thousands of linked microprocessors that perform extremely complex calculations. At the other end are tiny computers embedded in cars, TVs, stereo systems, calculators, and appliances. These computers are built to perform a limited number of tasks.

The personal computer, or PC, is designed to be used by one person at a time. This section describes the various kinds of personal computers: desktops, laptops, handheld computers, and Tablet PCs.

Desktop computers

Desktop computers are designed for use at a desk or table. They are typically larger and more powerful than other types of personal computers. Desktop computers are made up of separate components. The main component, called the system unit, is usually a rectangular case that sits on or underneath a desk. Other components, such as the monitor, mouse, and keyboard, connect to the system unit.

Laptop computers

Laptop computers are lightweight mobile PCs with a thin screen. They are often called notebook computers because of their small size. Laptops can operate on batteries, so you can take them anywhere. Unlike desktops, laptops combine the CPU, screen, and keyboard in a single case. The screen folds down onto the keyboard when not in use.

Handheld computers

Handheld computers, also called personal digital assistants (PDAs), are battery-powered computers small enough to carry almost anywhere. Although not as powerful as desktops or laptops, handhelds are useful for scheduling appointments, storing addresses and phone numbers, and playing games. Some have more advanced capabilities, such as making telephone calls or accessing the Internet. Instead of keyboards, handhelds have touch screens that you use with your finger or a stylus (a pen-shaped pointing tool).

Tablet PCs

Tablet PCs are mobile PCs that combine features of laptops and handhelds. Like laptops, they're powerful and have a built-in screen. Like handhelds, they allow you to write notes or draw pictures on the screen, usually with a tablet pen instead of a stylus. They can also convert your handwriting into typed text. Some Tablet PCs are “convertibles” with a screen that swivels and unfolds to reveal a keyboard underneath.