computer terminal, a device that enables a computer to receive or deliver data. Computer terminals vary greatly depending on the format of the data they handle. For example, a simple early terminal comprised a typewriter keyboard for input and a typewriter printing element for alphanumeric output. A more recent variation includes the keyboard for input and a televisionlike screen to display the output. The screen can be a cathode-ray tube or a gas plasma panel, the latter involving an ionized gas (sandwiched between glass layers) that glows to form dots which, in turn, connect to form lines. Such displays can present a variety of output, ranging from simple alphanumerics to complex graphic images used as design tools by architects and engineers. Portable terminals frequently use liquid crystal displays because of their low power requirements. The terminals of pen-based computers use a stylus to input handwriting on the screen. Touch-sensitive terminals accept input made by touching a pressure-sensitive panel in front of a menu displayed on the screen. Other familiar types of terminals include store checkout systems that deliver detailed printed receipts and use laser scanners to read the bar codes on packages, and automatic teller machines in banks.

Site and installations for the takeoff and landing of aircraft. Early airports were open, grass-covered fields, called landing fields, that allowed a pilot to head directly into the wind to aid a plane's lift on takeoff and to decrease its speed on landing. In the 1930s heavier airplanes required paved runway surfaces. Larger planes needed longer runways, which today can reach 15,000 ft (4,500 m) to accommodate the largest jet aircraft. Air traffic is regulated from control towers and regional centres. Passenger and cargo terminals include baggage-movement and passenger-transit operations.

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