220-1201 Hardware Study Guide for the CompTIA A+ Core Series Exam

General Information

Hardware concepts are one of the most heavily emphasized areas of IT assessed on the CompTIA A+ 1201 exam. Around 25% of the questions on the test pertain to this area. You’ll need to be highly competent in identifying, using, and connecting hardware components and devices. The recent increase in remote work also makes it necessary to know about different devices that support that workforce. As you study, keep in mind that about half the hardware questions begin with a scenario.

Displays

The display is a hardware component that is used to show visual data. The type of display unit, also referred to as a screen or monitor, used for visual output has various components and attributes based on the technology employed by the unit. For the Comptia A+ exam, you should be able to compare and contrast different display units and their attributes.

Types

There are two primary types of mobile display units: liquid crystal display and organic light-emitting diode.

Liquid Crystal Display (LCD)

LCD is a display technology that uses a current passed through a semi-crystalline liquid sandwiched between two glass plates to produce images. The liquid crystals do not produce light and require a light source, the backlight, to display the image. The most commonly used backlight for modern displays is LED lighting.

There are three popular variants of LCDs: IPS, TN, and VA, all of which use liquid crystals and transistors to form patterns in different ways.

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In-Plane Switching (IPS)

With IPS, the liquid crystals turn parallel when voltage is applied, allowing the light to pass through. IPS offers the widest viewing angle and the best color reproduction. It is ideal for vertical mounting and those needing high-quality color, such as graphic and video artists.

Twisted Nematic (TN)

With TN, the liquid crystals rotate 90 degrees when voltage is applied, allowing light to pass through. As the oldest of the LCD technologies, TN has limited viewing angles and washed-out or blended color reproduction. Their minimal lag time makes them ideal for competitive gamers, and they are an inexpensive option for office use.

Vertical Alignment (VA)

With VA, the liquid crystals turn vertical when voltage is applied, allowing light to pass through. This offers the best contrast ratio of the three technologies and is a solid middle-ground choice with decent color reproduction and only a slight lag.

Organic Light-Emitting Diode (OLED)

OLED displays contain both the image-producing components and the light source in a single panel, which means there is no need for a separate backlight. An organic light-emitting compound is sandwiched between an anode and a cathode, which produces a current. The current runs through the electroluminescent compound, producing light. The structure of OLEDs allows them to be flexible for curved displays. Power consumption with an OLED is less than with an LCD, and the contrast ratio is higher, producing sharper images. OLED is popular in high-end monitors and smaller devices such as smartphones.

Note: If a device states that it is LED as opposed to OLED, it uses LCD technology with an LED backlight.

Mini Light-Emitting Diode (Mini-LED)

Mini-LED technology is a backlight technology used with LCD displays, which is used to create higher precision in light control by using a high density of very small LED lights. Mini-LEDs allow for increased contrast, brightness, and color accuracy compared to traditional LEDs.

Touch Screen/Digitizer

A digitizer is a device that takes analog input in the form of written or drawn content, such as by a finger or stylus, and converts it into digital images. The digitizer, commonly called a touchscreen, can be built into the display as the top glass sheet or as an overlay for the display screen.

Inverter

An inverter is a small circuit board located behind an LCD panel that turns DC current into AC current, which is needed by the backlight of the LCD display. Flickering screens and dimness are common signs of an inverter malfunction.

Attributes

Attributes of display units are the characteristics that indicate the features and image quality of the display. Attributes can vary significantly between display technologies but are quantified using common metrics such as pixel density, refresh rates, resolution, and color spectrum.

Pixel Density

Pixels are tiny individual dots that make up a display image. The pixel density, also referred to as pixels per inch (PPI) or dots per inch (DPI), is the number of pixels contained in a display unit; the higher the pixel density, the sharper the image. Pixel density is the number of diagonal in pixels divided by the diagonal size of the screen. For example, a 27-inch display with a screen resolution of 1080p (which has approximately 2,202.9 diagonal pixels) has a pixel density of approximately 81.

Refresh Rates

The refresh rate is the number of times a screen is updated per second, with higher refresh rates creating smoother image transitions. The refresh rate is measured in hertz (Hz), with one hertz equal to one refresh per second. A common refresh rate for standard display units is 60 hertz, while gaming displays use increased refresh rates of up to 240 hertz.

Screen Resolution

The screen resolution of a display unit is the number of pixels that can be contained in a display horizontally (width) and vertically (height). Screen resolution is commonly expressed as width times height. Common screen resolutions include 1080p, which is 1920 x 1080, 1440p, which is 2560 x 1440, and 4K, which is 3840 x 2160.

Color Gamut

The color gamut of a display is the color range that a display is able to reproduce. Color gamuts are indicated by the color standard used by the display. The most commonly used standards are sRGB, Adobe RGB, and DCI-P3.