Updated: 02/27/2019 by Computer Hope

A monitor may refer to any of the following:

Computer monitor

1. Alternatively referred to as a VDT (video display terminal) and VDU (video display unit), a monitor is an output device that displays video images and text. A monitor is made up of circuitry, a screen, a power supply, buttons to adjust screen settings, and casing that holds all of these components.

Like most early TVs, the first computer monitors were comprised of a CRT (cathode ray tube) and a fluorescent screen. Today, all monitors are created using flat panel display technology, usually backlit with LEDs. The image to the right shows an ASUS LCD monitor.

When was the first computer monitor invented?

The first computer monitor was part of the Xerox Alto computer system, which was released on March 1, 1973.

What are the different types of monitors?

There are essentially two types of monitors, with the second having two variations based on backlighting (CCFL vs. LED). The first (and oldest) is the CRT (cathode-ray tube) monitor, which was based on the same technology as early televisions. The second is the LCD (liquid-crystal display) monitor.

Why is a monitor an output device?

A traditional monitor is only used to display (output) information from a computer and provides no source of input. For this reason, a computer monitor is considered an output device.


Newer PCs, smartphones, and tablets have touch screens, which allow the user to interact with their computer by touching what is shown on the screen with their finger. If the monitor has touch screen capabilities, it is considered an Input/Output devices. However, if it has no source of input it is only considered an output device.

Types of monitor connections

Computer monitors have at least one of the following types of monitor connectors to connect to a computer.


Video adapters are available to convert from one type of connector to another, such as DVI to VGA or HDMI to VGA, and vice versa.

modern video ports

2. Monitor is a term used to describe the act of watching over someone or something.

3. A resident monitor was system software used with machines utilizing punch card input. Resident monitors came before, but was very similar to, an operating system.

CRT, Display, Hardware terms, Output device, RGB monitor, Security terms, Video terms