Miami PC

Miami PC
Understanding your PC
By Internet specialist Ed Melo

As people become more familiar with computers they buy more of them. As they buy more, computer manufacturers build them faster and the prices drop.As prices drop, more and more tasks become computerized and the cycle starts again.Frankly, you can't avoid computers, so it helps to understand them.
We examine how to use and understand the "PC" (personal computer).

1- Computer Systems.
Overview and Terminology.

Think of all the parts in your computer as the various instruments in a orchestra.

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Input.
An orchestra cannot start to play until the conductor gives them a command or input.
When you give input to a computer, you send it raw information, commands, instructions or data.
Most common input devices are keyboard and mouse.

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Processing
Musicians are trained to interpret the musical notes and turn them into music.The orchestra is, in fact, processing the musical notes.
A computer processes data in much the same way.It might calculate the interest of a loan, check the spelling of a document or play music.

The computer has to translate your keystrokes into information that it knows how to use (bits and bytes).Once the data has been translated into bits and bytes, the computer processes that information according to your instructions.Finally, it converts that information into human readable format.

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Output
After the orchestra has read the sheet music and decided which notes to play in their different instruments (output devices) the resulting output is music.
Computers after they have processed the data, they show you the results of that processing as output.
Computer output might be words on a screen, pages from a printer or music from the speakers.Output is information that is coming out of the computer.
Output devices are monitors, printers ...
GIGO means: garbage in, garbage out.The information that comes out of the computer is only as good as the information you put into it.

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Storage
The conductor might decide to record the music the orchestra played.That way he can listen to it anytime he wants.
In a computer if you want to keep a record of your work save your work by placing it in a storage device like a magnetic disk.A computer is a electrical appliance that works with bits and bytes made up of electrical charges.
When you turn off the power all data inside a computer is forgotten.
Magnetic disks don't need electricity to stay magnetized.Save your work as you go every few minutes to protect the data against unexpected power failures.

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Bits and bytes
The computer is an electrical device and it requires electricity to work and electricity only comes in two states - It's on or it' off.
There are millions of tiny circuits inside a computer and at any time, some of them have electricity running through them and some of them don't.
If the computer looks at a particular circuit and sees electricity, it says, "I see number 1".If it looks at the same circuit a second later and the electricity is off, it says, "I see number 0".A computer can only see ones and zeros caused by the presence or absence of electricity.
A computer can count up to one two billion times per second.The ones and zeros are referred to as bits.There are only two possible bits that can exist in a computer - 1 and 0.
The computer combines the bits into larger numbers of eight bits each, called bytes.A byte could be from 00000000 all the way up to 11111111.There are 256 possible combinations of 1's and 0's if you group them eight bits at a time.Every one of the 256 possible bytes is assigned to a different character that humans understand.All computers use exactly the same code.That's how they can send information to each other.

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A short history of computing
Computing devices of some sort, have existed since before there was electricity.
5,000 abacus ..., geared adding machines... and steam driven calculating engines.

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The first generation
The Second World War was a great motivator for governments to develop fast computers.
By 1941, the Germans had developed a computer called Z3 that aided in the design of missiles and airplanes.
The British also developed a computer called Colossus, to break German secret codes.
By 1944, IBM, Harvard University and the US Navy had combined to build the Mark I computer, to help the Navy calculate ballistics tables for its big naval guns.
The mark I was classified as a relay computer because it used some 50,000 electric relays to control the electricity in its many circuits.
Mechanical relay pic
Mark I pic
About the same time as the Mark I, another computer was being built at the University of Pennsylvania.The Electronic Numerical Integrator and Computer (ENIAC) was an improvement over the Mark I because it used 18,000 vacuum tubes instead of 50,000 mechanical relays to control the switching of its circuits.
ENIAC computed at speeds 1,000 times faster than the Mark I.Both ENIAC an Mark I computers received their input through dials and switches.The operators of these computers had to translate their commands into 1s and 0s first, then set the appropriate switches "on" and "off" to input the data before doing a calculation.
In 1951, Remington Rand Built the first UNIVAC (Universal Automatic Computer), which it sold commercially.UNIVAC featured a new type of memory that allowed it to store a program of instructions along with the data.It also featured the first Central Processing Unit (CPU), which concentrated all the data processing in a single component, rather than throughout the many circuits of the huge machine.Only large corporations or government agencies could afford one.

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The second generation
It began around 1956 with the use of the transistor instead of the vacuum tube.A transistor is also nothing more than a switch used to control the flow of electricity in a circuit, it is the fraction of the size of a vacuum tube, uses much less electricity and generates very little heat.
Now devices made of solid-state transistor could be much smaller than before.
Printers, disk storage, memory and stored programs start to appear in the market and they make computers more flexible and affordable for businesses.
Sales began to rise from manufacturers like Burroughs, Honeywell, IBM and Sperry-Rand.

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The third generation
It saw reduction in size and increase in speed.
I the early 1960s the first integrated circuit (IC) was invented by the Texas Instruments Company and it began to appear in computers.
It combined three transistors onto a single silicon chip.
The 1970s saw large scale integration (LSI) where hundreds of transistors where placed on one tiny chip.
Next was ultra large scale integration (ULSI) where millions of components were put in a chip.
Computers were still only used by businesses.

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The fourth generation
The invention of the personal computer (PC), or desktop, marks the beginning of it.
Everyone could afford now to buy a computer and some companies like Apple, Atari, and Commodore all brought computer products to the market.
IBM began to recognize that there might be a market for PCs and made the first PC in 1981.
Manufacturing companies like Compaq, Dell and Hewlett-Packard appeared.
Each sold its brand of IBM clone PC.
By 1991, more than 65 million PCs were in use in the US.
In 2002, 90% of all PCs sales in the world were IBM type computers,but less than 7% were actually made by IBM, Apple makes the other 10%.

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The fifth generation
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Features: voice recognition, expert systems (Is the storage of the knowledge and expertise of some people in a system).
We are just about at the limit of how many components we can pack onto a silicon chip.In order to get any smaller, we have tocome up with a totally new technology.
Scientists are working on superconductors, a way to make electricity to move from place to place without resistance, or heat, which will allow us to make even smaller and faster chips.

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Programs evolve too
We have talked, so far, only about hardware.
Software consists of all the programs that you load onto your computer, it is simply a set of instructions for the computer to follow, software controls everything about the hardware.
If somebody invents a new microchip or a new printer, these devices are useless to us until a programmer writes software that can control them.
Software development has been just as revolutionary as the changes in hardware.

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Kinds of software
1-system software and 2-application software.

1-Performs the computer's housekeeping chores and makes sure all the parts of the system work smoothly together.
You use your System software to load an application program that specializes in what you want to do.
System software is also called Operating System.Exemple: DOS, Windows 98, Windows XP, ...
You don't have to give any commands to load the operating system into the computer, this is done automatically when the PC is turned on.
2-With application software programs you can get real stuff done.Example: Word processors (Microsoft Word), browsers (Internet Explorer).

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Software Improvements
Computer programmers are constantly writing new and improved versions of their software.New hardware requires that new software be written before we can use it.Sometimes a new version is released to correct problems from older versions or just to increase sales.
In the 1980's the first IBM PC used an operating system called DOS.Version 1 could start up the computer, load a few programs, save your work to a floppy disk.Version 2 could control the new hard drives.Versions 3-6 were written until 1994, each version gave the computer a little more power, we were able to buy bigger hard disks, more memory or faster processor chips.
One application that was responsible for the popularity of the IBM PC was a spreadsheet application called Lotus 1-2-3.

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GUI
DOS was difficult to use, commands had to be typed into the keyboard, users had to follow a complicated command structure.
All changed when Microsoft produced their first Windows operating system.Windows is a GUI (Graphical User Interface).Instead of typing long commands, you click little icons on the screen.

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Windows is an operating system that give applications like: spreadsheets, word processors, email programs, diagnostic tools and programming languages a friendly look and feel.You still have to learn to use them all.

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How to hook your computer up
There is a right way and a wrong way to hook it up.

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Location
A good location will add years to your computer's life.
Chose a table that is solid and sturdy.Vibration can loosen or damage the computer's components.
Keep the printer on a separate printer stand.
Leave at least three inches of space all around the computer and monitor.
Check the fans in your computer to make sure they are not blocked with dust.
Keep the computer away from sunlight and traffic.
Plan where you will be routing the cables for your system.All cables should be placed behind the desk.
Coil the cables into neat loops, secure them with tape.
Buy a power bar with six or eight outlets on it, with surge suppression which protects your equipment from fluctuations in the electricity.

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Ergonomics
It is the design of work areas and tools according to human characteristics.
Repetitive strain injury or carpal tunnel syndrome is a painful nerve disorder caused by a build up of tissue in the nerve channels of the hand and wrist.
You can get it by typing for long periods of time with your hands and wrists at an improper angle.
Your arms are supposed to point slightly downward from the elbow so that your hands are not angled back at the wrists.Use a sliding keyboard tray that pulls out from under the desk.
Buy wrist pads to keep your wrists at the right angle.
Most monitors are placed too high or too low on the desk for comfortable viewing, the result is neck pain and fatigue.Buy a comfortable chair that is fully adjustable.Put it as high as possible while keeping your feet on the floor and angle the seat slightly forward to prevent back pain.
Take a break every hour, move around to circulate the blood and flex your fingers.

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Unpacking and assembling the hardware
Identify the monitor, printer and the computer console or system unit.
Check the list of items shipped, make sure everything is there.Keep the original packaging just in case something is missing.
Always start with the system unit, unpack it and place it on the desk.
Now unpack the monitor, place it on the desk, unpack the printer, place it on the printer table.
Place the keyboard in front of the monitor.
Read the instructions on how to hook up the components: wires, mouse and cables.
Plug the power wires in the back of the units.
Don't turn on the power until everything is conected properly.
On the back of the monitor and PC there is a 3-prong plug for the power cord.
Connect the monitor to the PC.
There is a D-shaped male connector with 15 pins arranged in three rows and two twisty knobs attached to screws that are used to secure the connector to the back of the system unit.
Now look at the back of your system unit for a female connection the same shape with 15 holes.
Push the monitor cable into it and tighten the little knobs.

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Printer
Check the manual that came with your printer and connect it now. There are two kinds of cables used to connect printers. Besides the power wire, there will be another connector, or port, where the data cable to the PC will attach. If the connector is metal, three inches long, 25-pin, D-shaped and has a wire clip at each end, you have a PARALLEL printer connection.
If the connector on the printer is a small square or flat hole you have a USB connection. No matter which kind of cable you use, only one end of the cable can possibly attach to the printer and the other end attaches to the PC.
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USB is an acronym for Universal Serial Bus, you can plug anything into a USB port and it will work, as long as the device was made for USB.Computers come with USB ports for printers, scanners, digital cameras, etc.
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Connect the keyboard, the connector is round and there is a sign over the plug showing a picture of the keyboard.
Connect the mouse, the connector is also round and there is a sign over the plug showing a picture of the mouse.
If you PC has no round port for the mouse, then it's a serial mouse that connects to a serial port. It is a 9-pin male connector on the PC that matches the 9-pin female connector on the mouse's tail.
Connect the speakers and microphone into the sound card in the back of your PC. Connect only one of your speakers into the jack labeled line out or speaker out, assuming the jack is not color coded. The other speaker plugs into the first speaker. The microphone connects in line in, assuming the jack is not color coded.

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Connect to the internet
There are two ways to connect to the internet:
1-Through a MODEM, using the telephone line.
2-Via a faster BROADBAND connection, provided by the cable company.
Modems come in two styles and have two types of connections.
They can be internal (inside the PC), or external where they sit on the desktop.
Internal modem: look for two female telephone plugs in the back of the PC. One end of the telephone wire goes into the wall telephone outlet and the other end goes in the hole on the back of your PC marked "line". Plug your phone into the other jack hole in the back of your PC, so you can talk.
External modem: the modem connections are the same as above, but there are other two connections, one provides electricity to the modem, the other connects the modem to the computer. Connect the serial cable that has a 25-pin male connector at one end and a 25-hole female connector at the other.
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Serial ports on PC's come in two sizes 9-pin and 25-pin, if at the end of the job you have a large plug and one small hole you can buy an adapter in a computer store.
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If you plan to connect to the internet with a high speed broadband connection, then you have another specialized external modem that comes from your Internet Service Provider. Hooking it up is similar to hooking up an external telephone modem, except that the cable company has to drop a new line into your computer room. High speed modems connect to the PC through a USB port.

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Tower
Your computer has individual components linked together by cables. Your PC's System Unit (the big box) is the heart of the computer. Everything that goes in or out of the computer must pass through the system unit.
In front of your system unit you have buttons and lights that help you control it.

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The back of your PC
The expansion slots are long rows of metal plates. Some slots are just plain metal covers that protect an empty slot in the PC, if you were to buy an additional component, it might get inserted into one of those slots. While other slots have little connector ports coming out of them.
You might decide to buy additional parts for your PC later on, like a sound card for example, all components look like little circuit boards and they snap into the slot in the back of the PC.
Always turn off your PC before opening it, buy a anti-static wrist strap which you can use to ground yourself to the PC chassis. A static shock could destroy a computer chip.

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Slots
To get to those slots you have to take the cover off the system unit to expose the internal parts.
To add a new expansion card to your system, you have to remove one of the metal cover plates from the back of your PC.
They are almost always held in place by a single screw. Snap the new card into the slot and fasten it by using the screw that held the cover plate.
Then you can close the PC up again and start working with your new adapter.

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Inside the case
Drives

1-Hard disk, it is the main storage area for your operating system, your application programs and your data files.
2-CD-ROM drive and 3-Floppy disk drive are both used to get data in and out of the PC.
You cannot see the hard disk because it is inside a 3X5 inches airtight sealed metal box screwed into the chassis.
A hard disk is a hard metal disk that record, save, create, change and erase data magnetically. Hard disks have their capacities measured in gigabytes (billions of bytes). The more data they can hold the more expensive they are.
CD-ROM are used to install new software on your PC, play music CDs and for reference programs like electronic encyclopedias.
CD-ROMs hold between 600 and 700 megabytes of data.CD-RW are drives that can record or "burn" new CDs, you can use them to record music or carry files that are too large to fit on a floppy disk.
Some CD-ROM drives are also DVD drives, they have the special laser and lenses inside that allow them to read a much denser DVD.
Programs have become too big and complicated to fit on floppies anymore. A floppy disk can only hold 1.44 megabytes, you can fit over 500 floppies on one compact disc. Floppies are only used today to move small files from PC to PC. Floppies are easily erased and are reusable.

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Motherboards
It is the most important component in a PC. It is the large green circuit board, many of its parts are permanently installed. Every other component in the PC connects to the motherboard in some way.
CPU, memory, drives, keyboard etc send and/or receive data that travels through the motherboard.
Some motherboard manufacturers will build certain parts right into the motherboard (on-board components), so you don't have to buy them as adapter cards later on. You don't pay extra for on-board components and they help free up other expansion slots for future growth. The bad news is that they can't be upgraded or repaired, without replacing the entire motherboard.
If the video connector is directly wired to the motherboard and not on an adapter card, then you have on board video.

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CPU
It is the most important part on the motherboard. When Intel comes out with a new model of processor they change its shape and location on the motherboard.
Locate the CPU by looking for a small electric fan that is connected to a block of metal or heat-sink. The fan and the heat-sink are responsible for keeping the CPU cool. The CPU is a large computer chip that sits underneath the heat-sink directly on the motherboard.

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Memory
Your computer's memory is also on the motherboard, where the CPU can access it quickly.
RAM is one or more small circuit boards with rows of chips on them. They will be standing upright on the motherboard.
The total memory in your PC depends on the size and quantity of memory chips installed on the motherboard. PCs running Windows XP have 256 megabytes of RAM or more.

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Expansion Slots
Your PC will have a few expansion slots to allow you to add new cards and components later on. They are always located on the motherboard, near the back of the PC, so that any card you snap in will be able to poke its connector out the back of the PC. Some of your expansion slots already contain adapter cards, such as a video card or a modem.

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Power
The power supply's main job is to take the electricity from the wall and convert it to the correct voltages required by the parts and also cool all the components inside the system unit.
It contains a small fan that spins constantly, whenever the PC is turned on.
The power supply is a large silver box with lots of yellow, red and black wires running out of it. The colored wires all lead to the disk drives and the motherboard. The outside of the power supply is where the power cord connects.
If there is a problem with the power supply replace it, never open it, it is not serviceable.

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What is a CPU?
CPU stands for Central Processing Unit. It is a microchip within the system unit and is often referred to as the microprocessor or simply the processor.
One of its jobs is the control of information flow between components and calculates numbers when required.
Information is constantly flowing back and forth between the various parts of the PC and the CPU stands in the middle, deciding what goes where.
When you type at the keyboard, the CPU receives every keystroke and redirects it to the right place. When you print a letter, the CPU takes the characters from the screen or the disk and sends them streaming out the printer port and down the cable.
The CPU notices that some of the data flowing by is a command to perform a mathematical calculation. It stops the traffic for a second and adds up the next two numbers going by. Then it returns to its traffic control duties.
It's a good thing that CPUs are very fast. The operating speed of the microprocessor is the major factor in determining the power of the computer.
Where is the place to where the CPU redirects information?
What gives the CPU the command to stop controlling and start calculating?
The place is the computer's electronic memory, or RAM.
The "commander" and the "brains" that directs the CPU is the software program that's also in memory. If the CPU were not constantly being told how to do things, it wouldn't do anything at all. Some of the information being shuttled around by the CPU takes the form of program commands that tell the CPU what to do with the data.
The CPU has to work very closely with memory, because the most powerful processor can only juggle eight characters at one time. All the other numbers, letters and pictures on the computer's screen are really in memory if the CPU does not have to do anything with them right away. Eventually, the CPU will get around to handling all the information waiting to be processed.

The price of a computer depends mostly on the speed of the CPU, the capacity of the hard disk and how much RAM it has.

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How CPUs are named
The microprocessors used in IBM compatible computers have all been invented by Intel Corporation, or copied by companies that duplicate, or clone Intel.
Originally, Intel used model numbers to describe their processors. Today, Intel uses names like Pentium (1,2,3...), to describe their processors and then add a number after that to describe which generation of Pentium. The higher the number, the more powerful the CPU.
The Intel 8088 microprocessor was used in the original IBM PC in the 1980s. Lately, it was developed other processors like the 80286 for the IBM AT, the 80386 that was powerful enough for Microsoft to run its new Windows operating system, the 80486 that runs Windows 95 and it is the first processor that requires a cooling fan mounted right on the chip, and the Pentium.

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Pentium
It was supposed to be called the 80586, but Intel realized that other manufacturers were making 80586 clone CPUs and a judge determined that numbers can't be owned by anybody. So the name was changed to Pentium. Over the years, Pentium has gone through many name changes.

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Celeron
Intel has offered all of its processors in two or three "trim levels". When CPUs had numbers instead of names, you could buy the 80486SX, which was the economy model, or the 80486DX, which was the more expensive model. The SX versions would have a few features disabled during manufacturing.
The Celeron is simply a trimmed down Pentium, it doesn't have the same processing power as Pentium, so certain tasks will take a little longer to perform, but in the end it will save you money.

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Clones
Not all IBM compatible PCs have a CPU made by Intel. Many manufacturers developed less-expensive CPUs that emulated the Intel's capabilities with varying degrees of success. It is illegal to copy another company's chip, but it is possible to engineer a CPU that understand the same instructions and performs the same tasks.
One of the most successful clone manufacturers is AMD (Advanced Micro Devices), they regularly announce new microprocessor to keep up with Intel's designs. Some people think AMD is as good as Intel or better. AMD is cheaper than Intel. Next time you buy a new computer ask if they have a comparable AMD model.

The various CPU models are limited by their design to how much memory they can use. This is called Maximum Addressable Memory (MAM).
The 8088 only had enough internal circuitry to talk to, or address, one million bytes (one megabyte of memory). The 286 could address 16 megabytes. Today processors address billions, or gigabytes of memory. MAM is a technical specification for how much memory you could theoretically put in a PC. If the technician says you are maxed out (you can't add more memory), the limitations of the CPU might be the reason.

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Hertz
Computer processors work at a fixed speed, or frequency. The frequency is the speed at which the processor can send or receive data per second (send, fetch). The original Intel 8088 processor worked at 4.77 million hertz per second. The original IBM PC was a 4.77Mhz (megahertz) machine. Today we measure the processor speed in gigahertz, that's billions of hertz per second.

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Upgrading
It is not cost effective to perform a processor upgrade because there are also too many components that will need to be changed. Today it is only cost effective to buy a new hard disk and additional memory. This is cheaper than buying a new computer.

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Memory
Since the CPU can only work with a couple of characters at a time, it needs another temporary location, the memory, to store whatever you are working on.
Your computer works like an office. When you want to work on a letter, for example, you get out the file opening it in the computers memory, work on it a while, and then close the file when you're done.
If you have just typed a letter and you can see it on the screen of your word processing application, then both the letter and the word processor are in memory right now. Unless the information you are working on is in memory, along with the application that knows how to work on it, you can't do anything with a computer. When your letter, or whatever, is finished, you have to save it to disk. In Windows-based programs, you can use the file save program.

If you don't have enough memory, the system runs slow or won't run at all. If you have too much, it is just a waste of money. If it's not set up correctly, some programs won't load. If you turn off the electricity, it forgets what you were working on.

The computer's memory is not permanent. The computer can record your work on a paper as a print out, or on a disk.
Your computer's memory is electronic . It's made of rows of little microchips. Microchips push electrons around, electrons come from electricity. If something happens to the electricity in your computer any work that has not been saved to disk is lost.

Disk drives become the place for long-term storage. They store their data magnetically, just like a tape in a VCR.

When you buy software programs like word processing, accounting, design, graphics, etc, they come in a CD. They may be installed onto your computer's hard disk so you can get to them quickly, but they don't do their work there. When you are ready to use a program, you must load it into memory.
All programs are kept in disk, so they are safe when the computer is turned off.

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Where is the Memory?
The memory is sitting on the motherboard in straight rows of identical chips. RAM and ROM are the two major types of memory on your computer.
When people talk about memory they are generally talking about RAM (random access memory). The term random access means that the microprocessor does not have to search through every character in memory when it needs only a certain piece of information, that's why computers are fast. It goes directly to the part that it needs and reads it. Just like a CD, you can get to a song faster in a CD than in a cassette tape. Tapes are not random access they are sequential, it means you have to fast forward and reverse the tape until you find what you want.
ROM stands for read-only memory, you can't write anything on that chip. A ROM is a chip that contains a simple program or set of instructions that start your computer when you turn on the power. ROM does a few internal tests of the PC and then it loads the operating system (Windows or any other) from disk into RAM memory. Once the operating system is controlling the computer from RAM memory, the ROM can go back to sleep until the next time you turn your PC off and on. Just like a calculator.

A byte represents one character in computer language. The word word is four bytes long. The byte is the basis for all measures. Each kilobyte (K) is about 1,000 bytes, a megabyte (M or meg) is about about 1,000,000 bytes, gigabyte (Gb) is about 1,000,000,000 bytes. 640K is about 640,000 bytes.

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Conventional Memory
When DOS, the first PC operating system, was written for machines with 8088 processors, the programmers limited the amount of RAM memory the microprocessor could use to 640K. We outgrew this limit a long time ago and DOS is still around today because some of the most popular software packages need DOS to work. No matter how much memory you have, DOS will say you have only 640K. On any IBM compatible machine, the first 640K of RAM is referred to as conventional memory.

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Upper Memory
Actually, the original 8088 processor could use a little more memory than 640K, up to one megabyte of memory. Remember that your computer has RAM and ROM for memory. Years ago, somebody made the arbitrary decision that the megabyte of potential memory for the 8088 processor should be broken down into two parts: 640K of conventional memory where it could talk to RAM, and another 384K of upper memory for ROM.
640K + 384IK = 1,024K, or 1 megabyte.
When the processor is talking to RAM, it's talking to conventional memory. When it is reading from ROM, it is working in the 384K upper memory area.

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Extended Memory
The Intel 80286 PC was able to use way more than just one megabyte of memory. A Pentium can address up to four gigabytes. Any memory installed over 1 megabyte is classified as extended memory. Windows uses a lot of extended memory, but don't use conventional or upper memory very much.

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Virtual Memory or Swap File
Your computer uses virtual memory when the real memory starts getting full. Virtual memory is a reserved space on your computer's hard disk.
Operating systems like Windows use it a lot. Suppose you have typed a 30 page letter. You can't see all 30 pages at the same time. Windows takes some of those pages and stores them on the disk temporarily to free up some RAM and keep your computer running fast. As you move through your pages, Windows will swap pages from virtual memory to RAM so you can view them.

The computer numbering system is based on twos, they have two bits 0 and 1. If you take the number 2 and keep doubling it, you arrive at 1,024, which is the closest you can get to 1,000. Somebody decided it would be a good unit of measurement and called it a kilobyte. So K is really 1,024. A megabyte is actually, 1,048,576. A 1.44M floppy disk holds 1,457,664 bytes. Just remember that kilo is a thousand and mega is a million.

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How much Memory do I have?
To find out watch the monitor screen right after you turn on the PC. PCs go through an internal diagnostic procedure that verifies the memory installed in the system by counting the bytes. If your operating system is Windows, look for the My Computer Icon, click the right mouse button, a pop-up menu will appear, point to properties on the menu and click the left mouse button. The system properties window will open and you can see the amount of RAM installed in your PC in the first page.

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How much Memory do I need?
If your PC runs Windows buy as much memory as you can reasonably afford.
Buy lots of RAM, but know when to stop. Windows 95 and 98 can't use RAM over 256M. This is a limitation of the software similar to DOS maxing out at 640K. Windows NT, Windows 2000 and Windows XP do not have this limitation and they can use whatever the PC can physically load.

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Memory Errors
Out of Memory means you have too much information for the memory to hold. Save your work, exit the software, and restart your computer. You probably need to buy more memory or your system is loading too many little programs and utilities in the background when it starts up.
General Protection Falt is a memory problem. Save your work, exit the software, and restart your computer. If it happens again call maintenance.
Parity Error happens when the CPU decides that memory is not giving it the right information. Check that all your cooling fans are working. Turn off your PC, wait 30 seconds and turn it on again. If it happens again call maintenance.

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Input Devices
Any equipment that can be used to get your commands into the PC is an input device. Example: keyboard, scanners, joysticks and mouse.
A computer Keyboard has much more capabilities than a typewriter, it can give commands, navigate through documents and type characters that don't appear on the keys.
The numeric keypad on the right hand side of the keyboard was made to look like a calculator. You multiply with the * and divide with the / key. The "5" key has a little bump, so you know where the other keys are just by touching it.
Press the numeric keypad (Num Lock) once (the light turns on), so the numeric pad can enter numbers, press it again and the keys turn into arrow keys and will move the cursor around.

The way some keys work on your keyboard depends on the application you are using at the time.
Some common uses:
Caps Lock forces the alphabetic characters into upper case, Esc (Escape key) cancels a command or goes back one step, Pause/Break pauses the screen from scrolling too quickly and when used with Ctrl may interrupt a command, Scroll Lock (Scr Lk) in spreadsheet programs, locks the pointer into a cell, so that moving the arrow keys moves the entire sheet instead of the pointer, Print Screen captures the image on the screen and sends it to either the printer or the Windows clipboard, Home moves the cursor to the beginning of the line and Insert switches between Insert and Over-type modes in a word processor.

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Ctrl and Alt
These keys have no use by themselves, they are always used in combination with other keys and what they do depends on the program you are using.
Example of shortcut keys: Ctrl+P will print your work, Ctrl+S will save it to disk, Alt (+ F, E, V, H...) accesses the command menu in Windows, Alt+F and then S will also save your work to disk.

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Ctrl+Alt+Delete
If you press these three keys at the same time it will restart your computer or it will bring up a window asking which program you want to terminate. It is only used when the computer has stopped responding. If you press them twice, it will restart your computer.

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F (Function) Keys
From F1 to F12, they are defined or mapped by the program you are working with at the time, they provide shortcuts to other commands. One key that is almost always the same is F1, the key that accesses the online help system for your program.

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Mouse
Its purpose is to give commands to a computer through a graphical user interface.
Engineers are always trying to improve computer mice. Some mice have trackballs, some have optical sensors, some are wireless and some are full of buttons and gadgets. You can use a mouse to point, click, right click, double click, drag, right drag and drop.
Windows has a special setting to reverse the mouse buttons for left-handed users in Control Panel, under Mouse.
Pointing devices in laptop computers:
The pencil Eraser is popular on IBM and Toshiba, it is a tiny knob set into the middle of the keyboard, it responds by sideways pressure by gliding the mouse pointer across the screen, the mouse buttons are located at the bottom of the keyboard.
The Touch-pad, you move the pointer around on the screen by touching the pad with your finger, when you need to click the mouse button, just tap the pad.
The Trackball is just a mouse turned upside down where you spin the ball with your finger.

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Mouse Problems
If the mouse pointer is jumpy or sticks on the screen it is because the rollers are dirty. Open the mouse with a screwdriver, clean the roller and the inside with a Q-tip and some rubbing alcohol. If the mouse pointer does not move, check if the mouse is properly plugged into the PC in the right place. Turn your PC back on again and watch for unusual messages during the start-up. If the mouse is still dead, you might have to buy another one.
If you have a wireless (or not) optical mouse, clean the lenses underneath it and finally, check the mouse's batteries.

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Fax Modems
If your computer has a dial-up telephone modem, chances are it is a fax modem as well. That means you can send and receive faxes and print them on paper. The fax modem needs software to make it work. Often computers come with some kind of free fax application.
To receive a fax, load the software into RAM and tell it how many rings to wait before it should answer the phone. The fax that you receive will pop up on the screen, so you can read it or print it.
If you want to send a fax, type the document and tell the PC to print it to fax modem, the program will ask you for the fax number to dial.
If you have a document in your hands and you want to fax it to someone, you have to scan it first.

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Scanners
A scanner gets paper documents into a PC and stores them as digital images. It works like a photocopier, moving a wand of light down a document, while taking a picture of it, and then, it sends the picture through a cable into the PC.
A scanner can scan a text document and convert the image into typed text by recognizing each character. This is called OCR (Optical Character Recognition) and it allows you to edit the scanned document in a word processor.

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Some types of scanners:
Hand-held Scanners are the least expensive and results depend on how steady your hand is.
Flatbed Scanners have a glass top like a photocopier. They are accurate because the scanning head is moved mechanically.
Specialty Scanners are scanners designed just for business cards, slides or pictures.
Work Centers, they combine scanner, printer, photocopier and fax in one machine.

Other Input Devices:Bar code readers, touch screens, digital cameras, graphics tablet and joysticks.
You can connect a digital camera or a memory card to a PC and transfer your pictures to disk, then you can preview, edit, email and/or print them.
The most important thing to know before buying a digital camera is the resolution. This means, how many millions of pixels (or mega pixels) the camera can use to compose the picture.

A pixel is a point of light (or colored dots) and it takes many pixels put together to form a picture. The resolution quality of printers, monitors, and cameras is measured in pixels. The more the better.

If you want to print digital pictures that are 4X6 inches, you should buy a camera with at least 2 mega pixels resolution. 5X7 inches use 3 mega pixels and 8X10 inches use a four megapixel camera.

A graphic tablet is a input device made to edit graphic images. The movements of the stylus (similar to a pencil) are picked up by the tablet and translated to the computer screen as drawing.

A joystick is a game controller. When you need to calibrate your joystick, go to Control Panel and look for an icon for game controllers.


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Output Devices
The Monitor (also called the screen or display) is your main source of output. Since so much time is spent staring at your monitor you should get a good one. Monitors used to come in different display quality, with names like CGA, EGA, and VGA. They are extinct today. You should buy at least a SVGA (Super Video Gate Array). An SVGA monitor is capable of the highest resolutions and can show the greatest number of colors.
Screen Resolution
The image on the monitor is made up of rows of colored pixels, or dots. The number of dots that the screen can display across one row, combined with how many rows of pixels can be fit on the screen determines the monitor resolution. On a VGA monitor, the highest resolution is 640X480. 640 pixels horizontally and 480 vertical rows. A SVGA monitor can display resolutions of 800X600, 1024X768 and 1280X1024.
If you view a large image, a low resolution screen can't show enough of the image at one time. You have to scroll the screen up, down, left and right and you can never see the whole image at one time.
When surfing the internet, many web pages are optimized for at least an 800X600 display.

Don't buy interlaced monitors. Some manufacturers build high resolution monitors with cheap electronics inside. They achieve this by INTERLACING. When the monitor refreshes the screen (which it does 60 times a second), it skips over every second row of pixels. Then it goes back and redraws the lines it missed in between. The result is a flicker that causes headaches.

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What is the Dot Pitch of the screen?
The distance between the pixels on a screen is called the dot pitch. The closer the dots, the sharper the picture. The bigger the dot pitch, the fuzzier the picture. The biggest acceptable dot pitch is 0.28mm and the best monitors are at least 0.25mm. To find out, read the specifications in the booklet that comes with the monitor or in the manufacturer's website.

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What is the Color Depth of the monitor?
The maximum number of colors that can be seen in your monitor is referred as color depth. How deep do you want to go?
The typical picture of a landscape with water, sky, trees and mountains contains over 16 million colors. When full color images appear blotchy on a computer screen, the reason is that the monitor is not displaying enough colors. Buy a monitor that can display 16 million colors (true colors monitor).

What is the video card (adapter)?
A monitor is only as good as the video adapter it is connected to. A video card sends the picture to the screen.

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What is the Size of the screen?
The size of a computer monitor is measured diagonally, from corner to corner and includes the parts of the picture tube that are hidden behind the casing. The most common sizes of monitors are 14, 15 (best suited for low resolution: 640X480), 17, 19 (for medium resolutions: 800X600 and 1024X768) and 21 inches (1280X1024).
LCD flat-Panel Monitors
The biggest advantages of an LCD (Liquid Cristal Display) monitor over a CRT (Cathode Ray Tube) monitor are its size, weight and energy savings.

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The Video Card
The video card is responsible for taking the digital signals from the CPU and turning them into analog signals that the monitor can understand. The video adapter is a small computer on its own. It calculates, at least sixty times a second, what color every pixel should contain. Make sure that your video card is capable of displaying the color depth and the resolution that you want to see on your monitor. Buy a good monitor and a good video card.The video adapter is a small circuit board that sits in a special slot just for video cards. In some computers the video adapter is built on the motherboard.

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The Video Card Memory
The video adapter needs its own supply of RAM, just so it can hold the images that it is displaying on the monitor.
This frees up the regular RAM in the PC for doing other things. Plus, since the video RAM sits on the video card, the images are processed a little bit faster than if they had to travel through the motherboard.
How much RAM do you have in your video card?
You need enough RAM on your video card to display the color depth and resolution you want to see on your monitor.
The three most common color depths are 256, 64,000 and 16,000,000.
In order for the video card to keep track of this colors, it has to assign different amounts of memory to each pixel on the screen.
It takes 8 bits of memory to keep track of the color in one pixel as long as there are only 256 possible colors.
It takes 16 bits of memory to keep track of the color in one pixel as long as there are only 64,000 possible colors.
It takes 32 bits of memory to keep track of the color in one pixel as long as there are only 16,000,000 possible colors.
We also have to take into consideration the resolution of the display.
If your preferred resolution is 1024x768, multiply those numbers and you get 786,432 pixels on the screen.
1280x1024 = 1,310,720 x 32 = 41,943,040 / 8 = 5,242,880 or 5.2 megabytes.
1024x768 = 786,432 x 32 = 25,165,824 / 8 = 3,145,728 or 3.1 megabytes.
800x600 = 480,000 x 32 = 15,360,000 / 8 = 1,920,000 or 1.9 megabytes.
720x576 = 414,720 x 32 = 13,271,040 / 8 = 1,658,880 or 1.6 megabytes.
640x480 = 307,200 x 32 = 9,830,400 / 8 = 1,228,800 or 1.2 megabytes.
Now you multiply that number by the number of bits per pixel required by your color depth.
16,000,000 colors uses 32 bits per pixel so, 32 bits multiplied by 786,432 pixels equals 25,165,824 bits.
This is how many bits of memory are required to fill a display at 1024x768, using a color depth of 16,000,000 colors.
There are 8 bits in a byte.
25,165,824 bits divided by 8 equals 3,145,728 bytes, or 3.1 megabytes.
So we need a video card with al least 3.1MB RAM on it if we want to use these display settings.
Video cards are sold with 1MB, 2MB, 4MB and 8MB of RAM. You would need a 4MB card in this case.
If your video adapter only had 2MB of RAM Windows would force you to reduce either the resolution or the color depth, so that the number of bytes required is less than 2MB.
You can buy more memory for your video card, just put it in the sockets of the card, this is cheaper than buying a new video card.
Some cheaper cards cannot be upgraded.

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