CompTIA Input/Output devices and display technology and management

what can cause this Display issue: Burn-in

- A fixed image is displayed on the screen for an extended period of time causing phosphor burn in CRTs or pixel deterioration in LCD and plasma displays. - Screen savers are used to combat burn-in.

Two types of warping of imagining due to display problems

- Barrel distortion - Pincushion distortion

what can cause this Display issue: Dim image

- Brightness level set too low. - On a laptop, the power plan is set to dim the display.

Here are the tabs present on the mouse properties dialog box:

- Buttons: Used to make changes in the configuration of the keys such as double-click speed - Hardware: Used to view the underlying devices and their properties - Wheel: Used to change the vertical and horizontal scrolling options

what can cause this Display issue: Color patterns incorrect

- Data connections not connected securely. - Adjustments needed to the display settings of brightness, contrast, color balance, or temperature. - If a CRT, the monitor might need degaussing due to magnetic interference around the monitor.

what can cause this Display issue: Artifacts

- Data connections not connected securely. - Graphics card overheating. - Graphics card driver is corrupt.

There are three main computer output devices:

- Display - Printer - Speaker

what can cause this Display issue: Blank screen on boot up

- Incompatible or corrupt graphics driver.

what can cause this Display issue: Dead pixels

- No voltage is getting to one or more of the pixel's subcomponents. - Sometimes turning off the display will reset dead pixels to their baseline state. Running a screen saver can help prevent dead pixels.

Keyboards

- The main input device on computers and laptops is the keyboard. It is - loaded as critical hardware during the computer boot process. - Now connected via USB, but old ones connect through a PS/2 connector - Some can be Bluetooth

KVM (keyboard, video, mouse) switch

- a box that allows you to use one keyboard, mouse, and a display device for multiple computers. - KVMP (keyboard, video, mouse, peripheral) switches are Newer KVM switches allow you to share other USB peripheral devices among multiple computers, such as an external hard drive. How you switch between computers has evolved since the first switch. The original KVM switches used a mechanical rotary switch. This evolved quickly to mechanical push buttons. The downside of mechanical switches is they are unable to send signals to any computer other than the one currently selected on the KVM. That means if you have a computer that is booting up, but not selected on the KVM, the computer won't detect a keyboard during the POST and gives you a keyboard POST error. In the early 1990s, KVMs changed to hot-key switching using software. These types of switches are called active switches and they can send signals to the computers that are not currently selected on the KVM, solving the keyboard detection issue at boot. Today, most KVMs are controlled through hot-key commands (for example, pressing Ctrl+Ctrl, Scroll Lock+Scroll Lock and the Print Screen keys.) Hot-key switching can include an on-screen display feature that lists the connected computers.

Touchpads

- are an input device where you move your finger over a touch-sensitive surface to move the pointer around the screen. - You'll find touchpads on laptops and incorporated into some external keyboards.

A mouse

- is used to move a pointer around on the screen and make selections from graphical items.

Configuring mouse settings

- use the Mouse settings utility built into your operating system or driver software. - Pointing devices have more configurable options than a keyboard.

Types of mice and how they keep track of movement

1. An optical mouse has an optical sensor on the bottom. 2. A mechanical mouse has a ball underneath.

To connect an external display device to a computer

1. Examine your display connections, and determine which one you will use. Digital connections are preferred over analog. Remember that VGA connections are not designed to be hot-swappable. You should power down your computer before connecting a VGA monitor. 2. If there is an onboard video port and a video expansion card, verify the one you won't use is disabled in the BIOS/UEFI, or that the motherboard is configured to autodetect which you are using. 3. Attach the display data cable to the back of the monitor. 4. If necessary, attach an adapter to the computer end of the display data cable. For example, if your display device has a DVI connection and your computer has a VGA connection, you would attach a DVI to VGA adapter to the computer end of the DVI cable. 5. Attach the display data cable to the computer's video port. 6. Plug the power cable into the back of the monitor, then into the wall outlet. 7. Install any software or drivers that came with the display device. Software and drivers provided by the display manufacturer will give you more features than the generic PnP display driver installed with Windows. 8. Use Control Panel, PC Settings, or the driver software to make any desired display setting changes for the external display device.

In addition to the typical QWERTY keys, keyboards can include additional keys, some of which might be specific to the operating system:

1. Function keys (F1 - F12) whose purpose is assigned by the system software. They can be used in combination with the Ctrl, Alt, and Fn keys to change their function. 2. Start menu key for opening the Windows start menu. 3. Menu key for displaying the shortcut menu of the current selection or location. 4. Arrow keys that move the cursor one space at a time. 5. Insert and Delete keys. 6. Scroll keys - Home, End, Page Up, and Page Down. 7. A numeric keypad for entering numbers and math operators ( + - * / ).

How You can connect a second (or third) display device to a computer, laptop, or mobile device

1. Identify the video port you will use on the computer, laptop, or mobile device. On a PC, you will need a second video port, or a video port that supports multiple chained displays. 2. For PCs, if you are currently using a graphics expansion card and want to use the onboard video port for your second monitor, verify the onboard port is enabled in the BIOS/UEFI. 3. Attach the display data cable to the back of the monitor. 4. If necessary, attach an adapter to the computer end of the display data cable. For example, if your display device has a DVI connection and your computer has a VGA connection, you would attach a DVI to VGA adapter to the computer end of the DVI cable. 5. Attach the display data cable to the computer's video port. 6. Plug the power cable into the back of the monitor, then the wall outlet. 7. Install any software or drivers that came with the display device. 8. If you connected an external display device to a laptop, you scroll through which screen(s) display data by pressing the FN key + the appropriate F# key. The appropriate F# key typically has a picture of a laptop and a box behind it to indicate a second display. The key combination rotates through display on internal laptop screen only, the external screen only, and both screens together. 9. Use Control Panel or the display or graphics card manufacturer's software to make any desired display setting changes.

If your touch screen begins to improperly interpret touch locations or inconsistently accepts touch input, you should try recalibrating the touch screen.

1. Open the calibration utility. o In Windows 7, open Control Panel > Hardware and Sound. Under Tablet PC Settings, tap Calibrate the screen for pen or touch input. o In Windows 8 versions, swipe from the right-side and in the Search box enter Calibrate. Tap Calibrate the screen for pen or touch input. 2. Tap Calibrate. In Windows 7, this is on the Display tab. 3. Tap Yes. To allow the program to make changes to Windows. 4. Follow the on-screen instructions to calibrate your touch screen, tapping where prompted. 5. Tap Yes. To save calibration settings.

Troubleshooting a blank display While a blank display might mean your display has failed, you should check the following items prior to purchasing a replacement display.

1. Verify the display has power. 2. Verify the display data cable is connected securely to both the display and the computer's display port. 3. Use the Windows Advanced Boot menu to boot into Safe Mode and check your resolutions settings. Setting the resolution higher than the display supports can cause it to go blank. 4. Verify your graphics card driver is compatible with your operating system. If not, obtain a compatible driver or replace the graphics card. Many display issues are due to incompatible hardware drivers. 5. Use Device Manager to check for problems with your graphics driver. Drivers marked with a red X or yellow exclamation point are not working properly. 6. Use the Windows Advanced Boot menu to boot into VGA mode to re-install or repair your display drivers. This mode loads minimal video drivers and uses a low-resolution setting (640 × 480), allowing you to diagnose and fix video card problems. 7. If you can see the initial boot screen when you turn on your computer, but it goes blank once Windows starts to load, boot into Safe Mode and use System Restore to repair Windows.

Transmissive

A backlight behind the panel shines light toward the user, making the display readable in low light situations. One drawback is that transmissive LCDs used in bright ambient light must have very powerful backlights.

CRT

A cathode ray tube display contains a large vacuum tube with a flat end covered in phosphors. An emitter in the back shoots a stream of electrons at the phosphors to create an image. Due to their bulk and expense, CRTs were displaced entirely by flat panel technologies, and you'll only see them on old computers today.

Input Device

A device that accepts information from the user and passes it to the computer for processing.

Biometric Device

A device that allows access to a computer or device by identifying a person through one of their unique physical characteristics.

Joystick

A device that controls the movement of the cursor on the screen.

Speaker

A device which converts an electrical audio signal into a corresponding sound.

Touch Screen

A display device that senses touch on its surface, then translates that touch to user input data.

Plasma

A flat panel screen that uses small cells filled with noble gases and phosphors to create color. An electrical current is applied to the gas to ionize it into a charged plasma, and each cell illuminates a pixel on the screen. Plasma screens were primarily used for large televisions in the late 1990s and early 2000s, but they've largely been replaced by LCDs.

Digital Camera

A hand-held device that records still images digitally instead of on photographic film.

Camcorder

A hand-held device used to record live-action video and audio.

LCD

A liquid crystal display is a flat panel screen that uses a liquid crystal solution sandwiched between two polarizing filters and glass panels. The liquid crystals are polarized using an electrical current, which straightens and twists them to achieve the desired color. In an LCD display, billions of liquid crystal molecules are constantly and independently being very rapidly pulsed on and off at different rates of power to create various shades of red, green or blue for each pixel. LCD screens are the most common displays used in external display devices and laptop computers.

Reflective

A mirror behind the panel bounces ambient light back to the user. Reflective displays are cheap and power-efficient, but difficult or impossible to read without ample ambient light. They're also more difficult to achieve with TFT displays, so reflective displays are generally passive matrix with all their drawbacks.

Display

A screen or projector that presents information from the computer to the user. Display screens can be an external or an internal component of a laptop or other mobile device.

KVM (Keyboard, Video, Mouse) Switch

A switch that allows a user to use one keyboard, mouse, and display device for multiple computers.

augmented reality (AR)

AR displays allow you to perceive your surroundings normally, but augment it with images, sounds, or other sensory information provided by the computer. For example, an AR display can superimpose text and visual indicators related to what you're seeing, such as showing patient monitoring data to a surgeon, or overlaying a blueprint-based model onto a construction site as a worker walks through it. Since AR displays must show the real world in accurate alignment with augmented elements, they can be more complex to design than VR displays, or have more demanding requirements for motion and positioning tracking. AR headsets may process input from eternal cameras, while AR glasses and head-up displays project augmented elements into a natural field of view. Even AR contact lenses are currently in development.

Touchpad

An input device where users move their fingers over a touch-sensitive surface to move the pointer around the screen.

OLED

An organic light emitting diode display is a flat panel screen that uses an organic substance as the semiconductor material in LEDs. Unlike LED, which uses an array of individual LED bulbs, OLED uses a series of thin, light emitting films. When you apply an electrical current, photons move through the organic substance and emit a bright light. OLED displays are becoming more common in laptop computers.

Display issue symptom: The computer crashes, leaving digital boxes from the image on the screen.. What is the issue and what could it be?

Artifacts - Data connections not connected securely. - Graphics card overheating. - Graphics card driver is corrupt.

Display issue symptom: The Windows logo appears during boot, then the screen goes blank.. What is the issue and what could it be?

Blank screen on boot up - Incompatible or corrupt graphics driver.

Display issue symptom: Faint, permanent images appear on the screen.. What is the issue and what could it be?

Burn-in - A fixed image is displayed on the screen for an extended period of time causing phosphor burn in CRTs or pixel deterioration in LCD and plasma displays. - Screen savers are used to combat burn-in.

Display issue symptom: Colors appear faded, muted, too dark, or too bright.. What is the issue and what could it be?

Color patterns incorrect - Data connections not connected securely. - Adjustments needed to the display settings of brightness, contrast, color balance, or temperature. - If a CRT, the monitor might need degaussing due to magnetic interference around the monitor.

Speakers

Convert digital signals from the computer into sound waves the user can hear. Computer speakers can be built-in to a laptop or a display, or an external peripheral device connected via a 3.5 mm audio connector to the sound out or line out (green) port on a sound card. Speakers can also be connected through the headphone jack on your computer or device. Bluetooth technology allows you to wirelessly connect speakers to your computer or mobile device. Speakers with an internal amplifier need a power source. Some obtain their power through a power adapter plugged into a wall outlet; others use a USB port on the computer; and some, like Bluetooth speakers, use battery power. External speakers typically produce higher quality sound than those built into a device. Higher-end computer speakers can include a subwoofer and the ability to manage equalization features such as treble and bass.

Display issue symptom: A pixel does not change color. It appears all black, or slightly red, green, or blue depending on which subcomponent of the pixel is affected.. What is the issue and what could it be?

Dead pixels - No voltage is getting to one or more of the pixel's subcomponents. - Sometimes turning off the display will reset dead pixels to their baseline state. Running a screen saver can help prevent dead pixels.

Display issue symptom: Not enough backlight to view pixels clearly.. What is the issue and what could it be?

Dim image - Brightness level set too low. - On a laptop, the power plan is set to dim the display.

Display issue symptom: Warping of an image so that a fixed point appears off axis. . What is the issue and what could it be?

Distorted geometry - Common in display projectors and is caused by a defect in the optic lens system. There is usually a slider that you can adjust to correct geometric distortions in a projected image. This might be labeled "Keystone."

Display issue symptom: The image appears skewed, or off-centered.. What is the issue and what could it be?

Distorted image - Typically caused by power problems or from other large appliances drawing from the same power source. - Try using a new power cord or a different wall outlet.

Display issue symptom: Image wavers or varies in brightness on the screen.. What is the issue and what could it be?

Flickering image - Data connections not connected securely. - The display might not support the selected display resolution at the current refresh rate. Lower the resolution to test. - An incompatible display driver. Obtain and install a compatible driver.

IPS

In-Plane Switching displays use crystals which are horizontally aligned with the screen rather than vertically as in the TN LCD. This allows the polarized crystals to move more freely into the desired alignment. IPS uses two transistors per pixel to improve the viewing angle over TN. However, this increases power consumption and decreases battery life in laptop computers. Advantages of IPS include the best viewing angles of all the LCD display technologies and the ability to produce the most accurate colors. Disadvantages include increased power consumption and slower response time.

Analog or digital connection

Most current external display devices have both digital and analog connection interfaces. If possible, use a digital connection, such as DVI, HDMI, or DisplayPort. With an analog connection, such as VGA, the computer's digital data must be converted to an analog signal that can be displayed on the screen. This can cause distortions in the signal.

Display issue symptom: Screen turns black, but the computer doesn't turn off.. What is the issue and what could it be?

Overheat shutdown - Typically an issue with high-performance graphics cards with a GPU, laptop displays, mobile devices, or display projectors that use incandescent bulbs. - Cooling systems aren't operating properly. - The display or device is operating in a hot environment. - Overclocking of GPU.

Display issue symptom: The icons, font, or screen is too big.. What is the issue and what could it be?

Oversized images and icons - The Windows Display setting for the size of text, icons, and other items is set to medium or large.

Dual input-output devices

There are some peripheral devices that both accept data to pass off to the processor and the display data to the user.

Configuring keyboard settings

To configure your keyboard, you can use your operating system's keyboard settings utility. 1. Open Keyboard settings. In Windows you can right-click the keyboard in Devices and Printers. 2. Generic keyboard settings include speed of character repeat and the cursor blink rate. o Repeat delay: When you hold down a key on the keyboard, after a certain amount of time it repeats itself. The amount of time between first pressing the key and when it begins repeating is the repeat delay. o Repeat rate: The speed at which the key is repeated after the repeat delay. o Cursor blink rate: The cursor blinks (flashes) on the screen to draw the user's attention to its location. The cursor blink rate changes how quickly the cursor blinks. Increasing the rate can help users locate the cursor more quickly; slowing it down is helpful for users who find the blinking distracting.

Printer

Traditional printers take information from the computer and render it using ink on paper for the user to view. 3D printers take information from the computer and create three-dimensional solid objects using photopolymer resin.

TN

Twisted Nematic displays use nematic liquid crystal in a perpendicular orientation confined between two plates of polarized glass. TN is the most common and oldest LCD panel type. Advantages include shortest response time, low power draw, high brightness when combined with LED backlighting, and low manufacturing cost. The chief disadvantage of a TN LCD panel is a very narrow viewing angle; the colors distort as you view the screen from the side and from above. TN technology is common for low-end displays, or for gaming displays or other applications where response time is important.

Transflective

Uses both a backlight and a partially reflective layer between the backlight and the LCD display to capture ambient light. This allows them to operate efficiently under a wide range of lighting conditions. Transflective LCDs tend to be more expensive.

VA

Vertical Alignment displays have crystals which are vertically aligned when there is no electrical current and horizontally aligned when current is applied. The former blocks light, producing a black image; the latter allows light from the backlight to pass through, producing a white image. With VA, there is no twisting of the crystals - they are either horizontal or vertical. VA displays have bright whites and deep blacks, wide viewing angles, and good color production. However, they have slower response times than TN or IPS, and VA monitors are typically more expensive.

Installing external keyboards

You install an external keyboard by simply plugging it in.

Input devices

accept information from the user and pass it to the computer for processing.

A capacitive touchscreen

also uses two layers. In the capacitive system, the layer with the electrical charge is placed directly on the glass panel. When you touch the screen, some of the electrical charge is transferred to you, causing a decrease in electrical charge at that location on the screen. The coordinates of the change in electrical charge are sent to the operating system and then the touch screen software translates this information into the correct user input. In a capacitive touch screen, in order to register input, some of the electrical charge needs to be transferred through the touch. This means you need to use something electrically conductive like a special stylus or your finger to touch the screen. Even a glove might interfere with the sensitivity. Since capacitative touchscreens work well with multi-touch and require little calibration, they're the dominant touchscreen technology today.

Filters

are attached or applied to the surface of a display to reduce glare on a glass screen from external light sources. They can be permanently installed as part of the display screen or purchased as an accessory to be added. Filters also reduce the viewing angle of the display. While you might think of this as a disadvantage, it can be a benefit. It decreases people's ability to surreptitiously view the display from the side, increasing privacy in the work environment. Privacy filters are especially useful where unauthorized people may be near displays used to view sensitive information, such as at the counter of a doctor's office.

MIDI-enabled devices

are various musical instruments, such as keyboards, guitars, drums, that come with a five-pin DIN MIDI connector and plug into the MIDI ports on a MIDI-compatible sound card. The MIDI device might come with a GUI software program that looks like equipment in a sound studio control room.

LCD technologies work by

blocking light rather than by emitting it. While an LCD panel consumes less power than an OLED or plasma display, that also means it is only visible with a light source.

Backlit screens

can use LEDs, an electroluminescent panel (ELP), or a variety of fluorescent light sources. In most cases there's a translucent panel between the backlight and the LCD in order to diffuse the light source and provide more even display brightness. Monochrome LCDs might have a yellow, green, blue, or white backlight, and color LCDs use white backlights covering most of the color spectrum. Unlike most electronic components, some backlighting technologies such as ELPs and fluorescent bulbs require high voltage alternating current power. While this is not a problem in a device that plugs into wall current, laptop computers that use only direct current internally have a small circuit board called a screen inverter attached to the display screen. The inverter takes DC from the motherboard and converts it into AC for the backlighting.

A plasma display

contains a neon/xenon gas mixture sealed between two glass plates. Within the plates is a grid of cells in which the gas mixture is charged. When the charged gas breaks down, it produces ionized plasma. This in turn emits UV radiation. The UV radiation activates color phosphors to produce red, green, or blue subpixels. Varying gas/phosphor reactions make it possible for a plasma display to produce over 16 million different colors. Plasma displays have a wide 160-degree viewing angle and are free of distortion at the edges of the screen. They are better at displaying motion graphics without blur. However, they are not as bright as other display technologies and consume more power. These features made them popular for home theater systems in the past, but maturing LCD technologies displaced them.

Output devices

display computer information to the user.

OLED

doesn't require backlighting to be seen in low-light conditions. They aren't as bright as backlit LCDs, but because they don't need backlighting, they can be thinner and lighter than their LCD counterparts. Advantages of an OLED display include the best picture quality of any display technology due to its ability to produce deep, dark blacks. They have a wide 160-degree viewing angle, a very high contrast ratio of 1.000.000:1, and quick response time. It's important to note that OLED displays can be slightly curved at the sides. However, they are expensive compared to LCD displays. They also have a problem with the material used to produce the color blue. It degrades at a much faster rate than the material for the other colors. This eventually affects the display's color balance and reduces its overall brightness.

LCD (liquid crystal technologies)

in general has a long-standing reputation for reduced contrast, poor black levels, and narrow viewing angles compared to other technologies such as plasma. While this is true for older LCD displays, gradual advancements in LCD technologies have improved screens greatly on all three counts. When evaluating an LCD display, examine its display characteristics, and if possible test it under the lighting conditions you'll be using it in.

A touch screen

is a display device that senses touch on its surface, then translates that touch to user input data. You interact with the information displayed on the screen using your finger or a special stylus instead of using a mouse or keyboard. Touch screens are used in many different applications - ATMs, point-of-purchase terminals, smartphones, tablets, laptops, and stand-alone computer monitors. In some laptop computers with touch screens, the screen rotates and lays flat, facing up, so that the user interacts with the laptop similar to a tablet. These are called 2-in-1 laptops.

The refresh rate

is a measurement of how often the display image is updated per second. It is expressed in hertz (Hz). Common display device refresh rates range from 60 to 144 Hz. As the refresh rate increases, it decreases how much the human eye can notice the image being redrawn on the screen (called flicker). Flicker is particularly a problem for old CRT devices, so refresh rate is most important when you use those displays. The refresh rate is actually controlled by the computer's video card, not the display device. However, the rate you choose must be supported by both the video card and the display device. If you select a refresh rate that isn't supported by the display, the screen will go blank or distort the image. The maximum refresh rate you can choose is also affected by the display's resolution. Lower resolutions (for example, 800 × 600) support higher refresh rates than higher resolutions (for example, 1600 × 1200).

Brightness

is a measurement of the intensity of the energy output of a visible light source with pure white having the maximum brightness and pure black the minimum brightness. In a computer display, optimal screen brightness varies based on the amount of ambient light. Setting the screen brightness to a high-level is useful only when you are viewing the screen under high ambient lighting. High brightness drains the battery power on a laptop quickly, which is why most laptops have a power setting that dims the display automatically when on battery power. For a projector, "brightness" has the additional meaning of total light output, measured in lumens. A brighter projector can create a larger image, or one which is visible in a brighter room. For a home theater projector used in a darkened living room, 1000-2000 lumens might be sufficient, while for a conference room or lecture hall with more ambient light you might need 3000-5000 lumens. Brighter projectors are more expensive, consume more power, and produce more waste heat.

A display projector

is a specialized computer display that projects an enlarged image on a large surface such as a wall, whiteboard, or movie screen.

A smart TV

is a television or set-top box with Internet connectivity and the ability to display dynamic Web content (Web 2.0). Smart TVs can receive traditional television signals, as well as access a variety of Internet content, such as email, online games, streaming media, and on-demand video content. Access to popular content is preloaded on the Smart TV. To access additional content, you need to add apps to your Smart TV via an "app store." App stores are specific to your device. Smart TVs are connected to your local network and can access data and other devices on your network. Some smart TVs have internal storage capabilities for photos, videos, and music files. Others have features such as Bluetooth that allows you to wirelessly connect headphones, or voice or motion-sensors to interact with the content.

Aspect ratio

is the measurement describing the width and height ratio of an image on the screen, expressed in width:height format. For example, "wide-screen" HDTV uses a 16:9 aspect ratio, so an HDTV screen is 16 units wide and 9 units tall, or almost twice as wide as it is long. Old-style CRT displays had an almost square aspect ratio of 4:3, matching that of old televisions. When wide-screen desktop and laptop monitors first became available, the 16:10 aspect ratio was most popular. Since 2008, the computer display industry has been dominated by 16:9 devices, matching that of modem television sets and frequently even using the same panels. A display can still show an image of a different aspect ratio, but it either needs to be stretched (causing distortion), cropped (losing the edges of the image), or picture boxed (black bands across the top and bottom or sides.)

Display resolution

is the number of pixels (individual points of light or color) displayed on a screen. The measurement is documented as horizontal pixels x vertical pixels. The size of your display and the resolution determine how sharp an image appears to the human eye. For example, an image on a 14" monitor with a 1600 × 1200 resolution appears sharper than it does at the same resolution on a 19" monitor, since it has a higher pixel density. Pixel density is often expressed as pixels per inch (ppi) in a display's statistics. Higher resolution provides more image detail, while high pixel density provides a sharper image. However, it's important to note that setting a higher resolution could make the image too small to view comfortably, depending on the software you're using and content you're viewing.

Native resolution

is the resolution that gives the best image quality on an LCD. LCD displays are unable to perform the calculations to resize an image from one resolution to another without affecting image quality. This is especially noticeable in resolutions that aren't multiples of one another. For example, if the video card sends an image signal in 1366 × 768 resolution and the native resolution of the LCD is 1920 × 1080, there isn't a one-to-one mapping of pixels. You'll notice the image distorts and quality suffers. Depending on the display, the quality difference might be minor or major. The other way around is even worse; displaying a 1920 × 1080 image on a 1366 × 768 display will either be impossible, or result in downscaling that causes fine details of the image to be lost or blurry. If you have an LCD display, you'll want to use its native resolution, or in some cases an even multiple of its native resolution.

Combination I/O devices

peripherals that have combine input and output functions into a single physical device. Ex: all-in-one printer/scanner using a single USB cable or an audio headset combining headphones and a microphone. Some important combined I/O devices include:; • Audio headsets • KVM switches • Set top boxes • Smart TVs • Touchscreen displays • MIDI instruments

Virtual reality systems

providing immersive 3D multi-sensory experiences have existed for a long time, but they're enjoying a new surge of popularity as PC and smartphone displays. A modern VR headset for a PC, such as the Oculus Rift, is a display containing stereoscopic displays, one for each eye, along with stereo output. Critically, a VR headset has some sort of motion tracking, allowing the wearer to look around within the virtual environment. This is typically accomplished by means of internal gyroscopes and accelerometers, and may include more advanced features such as eye tracking sensors. Applications for virtual reality include gaming, simulations, and training.

A set-top box (STB), also called a set-top unit (STU)

receives digital audio and video signals and then sends those signals to a display, such as a television set or computer display. It may also be able to run a variety of apps, much like a tablet or other mobile device. Set-top boxes can be manufactured to receive signals from the Internet (for example, AppleTV or Roku), satellite or cable television providers, or over-the-air television stations.

In an active matrix, or thin film transistor (TFT) LCD

there is a transistor at each intersection which controls the light for each pixel. Transistors require less electrical current to control the pixels, allowing the current to be switched on and off more frequently, thus improving screen refresh time. Active matrix displays are more expensive, but improved response time and image quality has made them the dominant display technology for PCs and mobile devices.

Surface acoustic wave technology

uses a glass panel with a receiving and a sending transducer mounted along the sides of the panel. A transducer converts one form of energy to another. For example, a pressure sensor can detect pressure, which is a mechanical form of energy, and convert it to an electrical signal. Reflectors on the glass panel reflect the electrical wave signals between the two transducers. Touching the screen disturbs the wave, allowing the receiving transducer to identify the touch event. To register a touch, you need to disturb the wave. Similar to resistive technology, you can do this with almost any object. Surface acoustic wave technology is best for displaying detailed graphics. Because it has no metal layer, it allows for 100% light throughput from the display (compared to the 75% of resistive and 90% of capacitive), presenting the user with the clearest picture on the screen. It is, however, more expensive than the other touch screen technologies, and doesn't support multi-touch.

Passive matrix

uses a grid of horizontal and vertical wires with an LCD element at each intersection. Each LCD element is a single pixel on the display screen. As current is sent through the LCD element, the liquid crystals at that location twist or straighten, allowing light to pass through or blocking it. Passive matrix displays were used by early LCDs due to ease of manufacture, but had slow refresh times, low contrast, and poor support for high resolutions. Today they're primarily manufactured for small devices and industrial applications where their disadvantages aren't a drawback.

A resistive touchscreen

uses two layers, a layer of glass and a conductive and resistive metal layer, with an electrical current running between them. The two layers are separated by spacers. When you touch the screen, the pressure on the screen makes the layers touch and there is a change in electrical current in that spot. The coordinates of the change in current are sent to the operating system and then the touch screen software translates this information into the correct user input. In a resistive touch screen, all you need to do is make the two layers touch to change the electrical current. This means that you can use any object to touch the screen. It doesn't need to be something electrically conductive like your finger. You'll want to avoid using hard, small objects like a pen tip, which can damage the layers. Resistive touchscreens are the easiest and cheapest to manufacture, but they require frequent calibration and can only register touch in one spot at a time. They're common in older devices, but less frequently found today.

Barrel distortion

where the perceived location of a point in space (the intersection of two of the grid lines) is farther away from the center relative to where it really is.

Pincushion distortion

where the perceived location of a point in space is closer from the center relative to where it really is.

MIDI (musical instrument digital interface)

which is a protocol for recording and playing back music on a computer.

VR headsets for mobile phones

work similarly to those for PCs. but use the phone itself as the display and the motion tracker, snapping into a pair of goggles that provides other functions

When comparing display devices there are various features you should take into account:

• Analog or digital connection • Aspect ratio • Brightness • Filters • Refresh rate • Resolution

If your touch screen is not responsive or is not responding as expected, there are several steps you should take to resolve the issue:

• Clean the screen with a soft, lint-free cloth using gentle pressure. You can dampen the cloth slightly with water or eyeglass cleaner, but never use alcohol, an alcohol-based cleaner, or soap. Don't apply fluids directly to the screen. • Restart the computer or device using a cold boot. A cold boot (also referred to as a hard boot) shuts the system down and turns off the power. A warm boot (also referred to as a soft boot) restarts the system without turning the power off. • Recalibrate the touch screen. • Use Device Manager to verify the HID-compliant touch screen driver is functional and current. You'll find the touch screen under the Human Interface Devices category. There shouldn't be a red X or yellow! next to the driver. • Check for and install any touch screen driver updates. Check with your computer or device manufacturer and your operating system manufacturer. • Check for electromagnetic interference by trying the touch screen in other locations. If you find the issue occurs in a single room or location, it is likely the touch screen is getting electromagnetic interference from something nearby. Interference is caused by small items such as a power strip or a lamp, as well as large items such as a large piece of equipment or server-rack. • If you suspect electromagnetic interference, test by turning off potential sources of the interference one at a time.

LCD display projectors have three main advantages over DLP projectors.

• Colors are more accurate. This is due to a clear section into the DLP color wheel. It boosts brightness, but reduces color saturation. • Slightly sharper images than the DLP at the same resolution. • Produces a brighter image than DLP using the same wattage lamp.

Set-top boxes must be connected to a power source, and come with a variety of display connection interface choices:

• Composite video • Component • HDMI • Stereo RCA • Digital audio via optical and coaxial digital • SCART • S-Video

Two important projector technologies include LCD and DLP.

• LCD is an older technology that uses mirrors and prisms to direct light through LCD panels and towards the projector's lens. Lamplight is projected through mirrors and prisms which split the light up into the primary colors of red, green, and blue. The three colors then are projected back through three glass LCD panels, each holding one color channel of the image. Like other LCD panels, individual pixels can allow or block light, creating three monochrome images. The separate colors are then converged using another prism, sent to the projector's lens, and the image is displayed onto the projection surface. • Digital Light Processing (DLP) is a newer technology that uses a single chip with a reflective surface composed of thousands of tiny mirrors corresponding to individual pixels. The mirrors move back and forth, varying the amount of light that is projected from each pixel towards the projector's lens. The DLP projects colors by passing the light from the lamp through a rotating wheel with red, green, and blue filters.

There are two prominent technologies used for modern display devices for computers and mobile devices, and two you may find primarily in older devices.

• LCD: external display devices and laptop computers. • OLED: laptop computers. • Plasma: old • CRT: old

LCDs use one of two technologies to polarize the liquid crystals: a passive or active matrix.

• Passive matrix • In an active matrix, or thin film transistor (TFT) LCD

There are three ways of illuminating an LCD panel.

• Reflective • Transmissive • Transflective

Touch screens use one of three technologies to recognize touch:

• Resistive • Capacitive • Surface acoustic wave

DLP display projectors have some advantages of their own:

• Smaller and more portable due to the use of the mirror chip instead of panels. • Produces deeper blacks than LCD, giving them a higher contrast. • Less pixelation, allowing for smoother motion graphics. • Higher reliability due to fewer moving parts.

One important indicator of an LCD's characteristics is the liquid-crystal technology it uses. There are three common types:

• TN • IPS • VA

An OLED display has four primary layers:

• The substrate, which acts as the structural framework. Red, green, and blue tinted plastic layers are added to the substrate to produce color. • The anode, which draws electrons. • The cathode, which provides electrons. • The organic layer, which contains two sublayers: a conducting layer (in which the electrons move) and an emissive layer (which produces light).

Troubleshooting no sound

• Verify the volume levels are high enough. • Make sure the sound is not muted. • Verify your speakers are the default sound device. • Verify the speakers are functional by connecting them to another computer or device. • For external speakers, verify the connectors are seated properly in the correct sound card ports and the sound card is properly seated in the expansion slot. For internal speakers, make sure the connector is seated properly on the motherboard. • If you have powered speakers, make sure they are turned on and receiving power. • In the speakers' Properties dialog box, on the Advanced tab, restore the default settings. • Run the Troubleshooting Control Panel applet and choose Troubleshoot audio playback. • Use Device Manager to verify the sound card driver is functional and current. You'll find the sound card under the Sound, video, and game controllers category. There shouldn't be a red X or yellow! next to the driver. • Check for and install any sound card driver updates. Check with your computer or device manufacturer and your operating system manufacturer. • Run the DirectX Diagnostics tool.