• Color capability
• Sharpness and viewability
• The size of the screen
• The projection technology

Color Capability 
Today, most desktop displays provide color. Older notebook and smaller computers sometimes have a less expensive monochrome display. The video displays can usually operate in one of several display modes that determine how many bits are used to describe color and how many colors can be displayed. A display that can operate in Super VGA mode can display up to 16,777,216 colors because it can process a 24-bit long description of a pixel. The number of bits used to describe a pixel is known as its bit-depth. The 24-bit bit-depth is also known as true color. It allows eight bits for each of the three additive primary colors red, green, and blue. Although human beings cannot really distinguish that many colors, the 24-bit system is convenient for graphic designers since it allocates one byte for each color. The Visual Graphics Array (VGA) mode is the lowest common denominator of display modes. Depending on the resolution setting, it can provide up to 256 colors. Figure shows the relationship between bit-depth and the number of colors that can be produced.

Sharpness and Viewability
The absolute physical limitation on the potential image sharpness of a screen image is the dot pitch. Dot pitch is the size of an individual beam that gets through to light up a point of phosphor on the screen. The shape of this beam can be round or a vertical, slot-shaped rectangle depending on the display technology. Displays typically come with a dot pitch of .28 mm (millimeters) or smaller. Dot pitch is a diagonal distance between the same color phosphor dots. The smaller the dot pitch, the greater the potential image sharpness.

The actual sharpness of any particular overall display image is measured in dots-per-inch (dots per inch). The dots-per-inch is determined by a combination of the screen resolution (that is, how many pixels are projected on the screen horizontally and vertically) and the physical screen size. The same resolution spread out over a larger screen offers reduced sharpness. On the other hand, a high-resolution setting on a smaller surface will produce a sharper image, but text readability will become more difficult.

Viewability is the ability to see the screen image from different angles. Displays with Cathode Ray Tubes (CRT) generally provide good viewability from angles other than straight on. Flat-panel displays, including those using light-emitting diode and liquid crystal display technology, are often harder to see at angles other than straight on.

The Size of the Screen
On desktop computers, the display screen width relative to height, known as the aspect ratio, is generally standardized at 4 to 3 (usually indicated as "4:3"). Screen sizes are measured in either millimeters or inches diagonally from one corner to the opposite corner. Common desktop screen sizes are 15-, 17-and 19-inch. Notebook screen sizes are somewhat smaller.

The projection technology used by most displays is Cathode Ray Tube (CRT) technology, which is similar to that used in most television sets. CRT technology requires a certain distance from the beam projection device to the screen in order to function. Using other technologies, displays can be much thinner and are known as flat-panel displays. Flat panel display technologies include Light-Emitting Diode (LED), Liquid Crystal Display (LCD), and gas plasma. LED and gas plasma work by lighting up display screen positions based on the voltages at different grid intersections. LCDs work by blocking light rather than creating it. LCDs require far less energy than LED and gas plasma technologies and are currently the primary technology for notebook and other mobile computers.

Displays generally handle data input as character maps or bitmaps. In character-mapping mode, a display has a pre-allocated amount of pixel space for each character. In bitmap mode, the display receives an exact representation of the screen image that is to be projected in the form of a sequence of bits that describe the color values for specific X and Y coordinates starting from a given location on the screen. Displays that handle bitmaps are also known as all-points addressable displays.