watchdog timer - a timer that expects to receive a pulse every fraction of a second. If a pulse is not received, it assumes the system is not operating normally, and a shutdown procedure is activated.

watt - a unit of power that is commonly used for electrical systems, but applies to all.

wavelength - the physical distance occupied by one cycle of a wave in a propagating medium.

word - 1. a unit of 16 bits or two bytes. 2. a term used to describe a binary number in a computer (not limited to 16 bits).

work - the transfer of energy.

write - a digital value is stored in a memory location.

WYSIWYG (What You See Is What You Get) - newer software allows users to review things on the screen before printing. In WYSIWYG mode, the layout on the screen matches the paper version exactly.