Computer Input Device

Webcam

A camera connected to a computer or server that allows anyone connected to the Internet to view still pictures or motion video of a user. The majority of webcam web sites are still pictures that are frequently refreshed every few seconds, minutes, hours, or days. However, there are some sites and personal pages that can supply streaming video for users with broadband.

The image to the right is a picture of the Logitech QuickCam Express and an example of what a webcam may look like. Today, most webcams are connected to the USB or Firewire port on a computer.

Digital Camera

A type of camera that stores the pictures or video it takes in electronic format instead of to film. There are several features that make digital cameras a popular choice when compared to film cameras. First, the feature often enjoyed the most is the LCD display on the digital camera. This display allows users to view photos or video after the picture or video has been taken, which means if you take a picture and don't like the results, you can delete it; or if you do like the picture, you can easily show it to other people. Another nice feature with digital cameras is the ability to take dozens, sometimes hundreds of different pictures. To the right is a picture of the Casio QV-R62, a 6.0 Mega Pixel digital camera used to help illustrate what a digital camera may look like.

Light pen
A light pen is a stylus with a light sensitive tip that is used to draw directly on a computer's video screen or to select information on the screen by pressing a clip in the light pen or by pressing the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen it is passed over.

Mouse
A mouse is a pointing device designed to be gripped by one hand. It has a detection device (usually a ball) on the bottom that enables the user to control the motion of an on-screen pointer, or cursor, by moving the mouse on a flat surface. As the device moves across the surface, the cursor moves across the screen. To select items or choose commands on the screen, the user presses a button on the mouse.

Joystick - computer hardwares
Joystick
A joystick is a pointing device composed of a lever that moves in multiple directions to navigate a cursor or other graphical object on a computer screen.

Keyboard
A keyboard is a typewriter-like device that allows the user to type in text and commands to the computer. Some keyboards have special function keys or integrated pointing devices, such as a trackball or touch-sensitive regions that let the user's finger motions move an on-screen cursor.
Optical Scanner
An optical scanner uses light-sensing equipment to convert images such as a picture or text into electronic signals that can be manipulated by a computer. For example, a photograph can be scanned into a computer and then included in a text document created on that computer.

The two most common scanner types are the flatbed scanner, which is similar to an office photocopier, and the handheld scanner, which is passed manually across the image to be processed.

Microphone
A microphone is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer.

voice recognition
A voice recognition module is a device that converts spoken words into information that the computer can recognize and process.

modem - computer hardwares Modem
A modem, which stands for modulator-demodulator, is a device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another computer. Each computer that sends or receives information must be connected to a modem. The digital signal sent from one computer is converted by the modem into an analog signal, which is then transmitted by telephone lines or television cables to the receiving modem, which converts the signal back into a digital signal that the receiving computer can understand.

Computer Output Device

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) to the outside world.

In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world. Inputs are the signals or data sent to the system, and outputs are the signals or data sent by the system to the outside.

The most common input devices used by the computer are the keyboard and mouse. The keyboard allows the entry of textual information while the mouse allows the selection of a point on the screen by moving a screen cursor to the point and pressing a mouse button. The most common outputs are monitors and speakers.


Visual display unit
A visual display unit (also called VDU, monitor, or screen) offers a two-dimensional visual presentation of information.a device that display information on a screen.

Speaker
A speaker can be used for various sounds meant to alert the user, as well as music and spoken text.
Printer
Printers produce a permanent hard copy of the information on paper.A computerperipheral that place texts on paper.

Installing Internal Hard Drives

Installing Internal Hard Drives

If your computer case has room for an additional drive inside, you may want to consider an IDE drive or the newer SATA drive.

Installing IDE Hard Drive
To install an internal drive, turn your computer off, disconnect the power cord, and remove the cover from the computer case. If you are replacing a drive, you will first need to remove the old one.

Start by unplugging the ATA ribbon cable and power cables, then remove the four screws holding it into the drive cage. Carefully slide the drive out of the cage - you may need to remove additional cables or expansion cards if space is tight inside your case.

Next, remove your new drive from its packaging and set the jumper on the back of the drive. If this is your primary drive, you will need to set it as master, though if it is an additional drive you will probably want to set it to slave.

Check the sticker on the drive itself, or the accompanying manual to see which pins to connect with the jumper in order to set the device as master or slave. Slide the new drive into the cage and secure it to the cage using four screws.

Next, attach the power and ATA ribbon cable. If you have set your drive to master, you need to attach the connector at the very end of the cable to your drive. If it is the slave, you will need to use the connector in the middle of the cable.

Check the connections to your drive, then plug your PC in and boot it up. It is often worth leaving the case off until you know the drive is functioning, as it is easy to set the wrong jumper settings or leave a cable improperly connected.

Windows will recognise your drive in My Computer. In order to use it, you must first format it, by right clicking and selecting format. If you currently use NTFS, you should set this drive to NTFS, otherwise use the FAT32 file system.

Alternatively, if this is a replacement for your primary drive, you will either need to mirror your old drives contents onto your new drive, or install operating system from the appropriate CD.

Install SATA Hard Drive
SATA connections are found in the newest computers which means that in most cases you will need to buy a SATA controller card and install it in an unused slot on your motherboard and then connect the SATA drive to the card.

Adding a SATA card is advantageous because once you have a SATA controller in your computer, you have the option to connect an external SATA drive. Installing a SATA drive in your computer is similar to installing an IDE drive as the drives are physically similar on the outside in terms of dimensions and mounting methods.

The difference is with the data connector, which is much smaller with a SATA drive than an IDE drive. SATA connectors have been known to break easily, so use caution when inserting and removing them.

Turn your computer off, disconnect the power cord, and remove the cover from the computer case. If you are replacing a current drive, you will need to remove the power and data cables, then unscrew the drive from the cage.

Carefully slide the drive out backwards, you may need to remove some additional cables and expansion cards if space it tight. Slide your new drive into the cage and secure it tightly with four screws, with two in each side of the cage. Next, you will need to plug in the SATA data and power cables.

The data cable needs to be plugged into your motherboard on the first available SATA channel. If you have replaced your primary drive, this would be SATA1, though if it is an additional drive, may be SATA2. Replace the sides of your case and boot your machine up.

Windows will discover your new hardware, though you can check that it is present in Windows Device Manager which is located in Control Panel. If you have replaced your primary drive, there will be no operating system present and you will need to install one using the appropriate CD.

Installing External Hard Drives

Connecting an external drive is much easier than installing an internal drive because you usually don't need to open the computer case. The drive attaches to a connector either at the front or the back of the computer case; power is supplied by a separate adapter.

Available connections
Your PC is likely to have one or more USB 2.0 connections; however it's less likely to have either FireWire or external SATA connections. FireWire and SATA connections are relatively simple to add, assuming your computer has at least one unused expansion slot.

If your PC has only USB 1.1 ports, you will need to add a USB 2.0 adapter in order to obtain usable transfer rates between your external USB drive and your computer. And if you need to add a USB 2.0, FireWire, or SATA adapter to your computer, you will need to open your computer's case and install the card.

USB Drive
Adding an external USB drive to your computer is as simple as connecting two wires. One wire is the USB 2.0 connection and the other connects to the drive's power supply. Plug the drive's power supply into an AC power outlet and then connect it to your drive.

For computers running Windows 2000/Me/XP, plug one end of the USB cable into an available USB 2.0 port on your computer and attach the other end to your drive. Windows will detect your drive and add it to your system. Open My Computer and you will see your drive listed among the other drives; you can now use this drive.

If you're using Windows 98 Second Edition, windows detects the new drive it will ask for software drivers. After you have installed the drivers, your new drive is available for use.

FireWire Drives
You can add external FireWire drives to your computer in the same way you would add USB 2.0 drive. Plug the power supply into an AC outlet and then into the drive. Connect the FireWire cable to the port on your computer and connect the other end of the cable to the FireWire port on the drive. Your drive is now available for use.

External SATA drives
Install the SATA controller card and then install the external interface extension in an empty slot in your computer case and connect it to the SATA controller card. You can then connect your external SATA drive to the SATA port in the rear of your computer. Close the computer case, plug in your computer's power cord, and turn on your computer. When your computer boots it will recognize your new drive, and the drive is ready for use.

Memory-Ram

There are two different types of RAM: DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory). The two types differ in the technology they use to hold data, with DRAM being the more common type. In terms of speed, SRAM is faster. DRAM needs to be refreshed thousands of times per second while SRAM does not need to be refreshed, which is what makes it faster than DRAM. DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds. Despite SRAM being faster, it's not as commonly used as DRAM because it's so much more expensive. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off.

In common usage, the term RAM is synonymous with main memory, the memory available to programs. For example, a computer with 8MB RAM has approximately 8 million bytes of memory that programs can use. In contrast, ROM (read-only memory) refers to special memory used to store programs that boot the computer and perform diagnostics. Most personal computers have a small amount of ROM (a few thousand bytes). In fact, both types of memory (ROM and RAM) allow random access. To be precise, therefore, RAM should be referred to as read/write RAM and ROM as read-only RAM.

See the "DRAM Memory Guide" in the Quick Reference section of Webopedia. This Webopedia Quick Reference offers general information on the two types of RAM and provide an overview on the common modules of each type.

Monitor

Monitor consists of a CATHODE RAY TUBE or also known as CTR. It is shaped like a bottle, it is a vacuum tube. The tube tapers near the back where there's a negatively charged cathode, or "electron gun". Electron Gun shoots at the back of the positively charged screen.

The screen is coated with phosphorous chemical. The chemical then starts to glow into individual points or dots called pixels. Pixels are the most important part of the display. It is because that an image is made of millions of tiny pixels. Distance between the pixels is important factor in image quality. If the distance between them is too great then the image will appear fuzzy. The closer together the pixels are, the sharper the image on screen.

There are a couple of electromagnets (yokes) around the collar of the tube that actually bend the beam of electrons. The beam scans (is bent) across the monitor from left to right and top to bottom to create, or draw the image, line by line. The number of times in one second that the electron gun redraws the entire image is called the refresh rate and is measured in Hertz (Hz).

If the scanning beam hits each and every line of pixels, in succession, on each pass, then the monitor is known as a non-interlaced monitor. A non-interlaced monitor is preferred over an interlaced monitor. The electron beam on an interlaced monitor scans the odd numbered lines on one pass, then scans the even lines on the second pass. This results in an almost imperceivable flicker that can cause eye-strain.

This type of eye-strain can result in blurred vision, sore eyes, headaches and even nausea. Don't buy an interlaced monitor, they can be a real pain in the ... ask your optometrist. Interlaced computer monitors are getting harder to find (good!), but they are still out there, so keep that in mind when purchasing a monitor and watch out for that "steal of a deal".

The monitor these days are judge by their Resolution or in other words video technologies. Resolution is defined as the number of pixels used to make an image. If you could count the pixels in one horizontal row across the top of the screen, and the number of pixels in one vertical column down the side, that would properly describe the resolution that the monitor is displaying. It's given as two numbers.

CRT - computer monitor
If there were 800 pixels across and 600 pixels down the side, then the resolution would be 800 X 600. Multiply 800 times 600 and you'll get the number of pixels used to draw the image (480,000 pixels in this example). A monitor can display 3 modes of resolutions, 640 X 480, 800 X 600 and 1024 X 768 and higher.

If you have set your monitor resolution to 1024 X 768 and your video adapter is capable of only 640 X 480, then that's all you can get.

Previously there were Monochrome monitors that only displayed one set of color. It was in DOS 80 characters across and 25 down. It was tough in those days as graphics were rough in comparison to today's capability, one had to change manually from text to graphic mode. But now due to the invention of graphic cards they do it for you. But the still flow the same rule.

Modem

Modem (from modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio.

The most familiar example is a voiceband modem that turns the digital 1s and 0s of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone Systems (POTS), and once received on the other side, converts those 1s and 0s back into a form used by a USB, Ethernet, serial, or network connection. Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps". They can also be classified by Baud, the number of times the modem changes its signal state per second.

Baud is not the modem's speed in bit/s, but in symbols/s. The baud rate varies, depending on the modulation technique used. Original Bell 103 modems used a modulation technique that saw a change in state 300 times per second. They transmitted 1 bit for every baud, and so a 300 bit/s modem was also a 300-baud modem. However, casual computerists confused the two. A 300 bit/s modem is the only modem whose bit rate matches the baud rate. A 2400 bit/s modem changes state 600 times per second, but due to the fact that it transmits 4 bits for each baud, 2400 bits are transmitted by 600 baud, or changes in states.

Faster modems are used by Internet users every day, notably cable modems and ADSL modems. In telecommunications, "radio modems" transmit repeating frames of data at very high data rates over microwave radio links. Some microwave modems transmit more than a hundred million bits per second. Optical modems transmit data over optical fibers. Most intercontinental data links now use optical modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x109) bits per second. One kilobit per second (kbit/s or kb/s or kbps) as used in this article means 1000 bits per second and not 1024 bits per second. For example, a 56k modem can transfer data at up to 56,000 bits (7kB) per second over the phone line.

Keyboard and Mouse

Keyboard is the main input device of a computer. Without a keyboard it is impossible to imagine working on a computer. Keyboard is a lot similar to a typewriter but has added keys that enhance the features and capabilities of a user working on a computer.

keyboard - computer hardwares
The today's keyboards consist of about 101 to 106 keys. The layouts are basically the same with the odd key situated differently. It is generally connected to the PS2 or the USB ports of the motherboard. There are many types of keyboards available these days, but one should always buy that is suitable and comfortable. Some are springy others have mushy feeling.

Yes, you get a keyboard when you buy a computer, but, it is not necessary that you have to use it. Keyboards are an inexpensive item that can be replaced easily. But, it doesn't mean that all keyboards are inexpensive as today's markets have very hi-tech keyboards.

Once you've found a keyboard that you find it comfortable, one of your main concerns should be proper typing form. Repetitive stress injuries are a concern and poor posture can also result in back and neck pain. Sit up straight and find yourself a chair that supports the natural curve in your back. It should be adjusted to your keyboard so that you don't have to lean forward or hunch to type.

Your shoulders should be relaxed with your forearms and wrists fairly level, fingers slightly curved. Wrist pads are made for you to rest your wrists on while taking short breaks, your wrists shouldn't be on them while you type. Don't sit and type constantly, try to take a few breaks every now and then and have a stretch.

Mouse
A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long documents.

Invented by Douglas Engelbart of Stanford Research Center in 1963, and pioneered by Xerox in the 1970s, the mouse is one of the great breakthroughs in computer ergonomics because it frees the user to a large extent from using the keyboard. In particular, the mouse is important for graphical user interfaces because you can simply point to options and objects and click a mouse button. Such applications are often called point-and-click programs. The mouse is also useful for graphics programs that allow you to draw pictures by using the mouse like a pen, pencil, or paintbrush.

There are three basic types of mice:

1. mechanical: Has a rubber or metal ball on its underside that can roll in all directions. Mechanical sensors within the mouse detect the direction the ball is rolling and move the screen pointer accordingly.
2. optomechanical: Same as a mechanical mouse, but uses optical sensors to detect motion of the ball.
3. optical: Uses a laser to detect the mouse's movement. You must move the mouse along a special mat with a grid so that the optical mechanism has a frame of reference. Optical mice have no mechanical moving parts. They respond more quickly and precisely than mechanical and optomechanical mice, but they are also more expensive.