A watch is a small timepiece intended to be carried or worn by a person, so as to make the time immediately and conveniently available. It is designed to keep working despite the motions caused by the person’s activities. A wristwatch is designed to be worn on a wrist, attached by a strap or other type of bracelet. A pocket watch is to be carried in a pocket. Watches evolved in the 17th century from spring-powered clocks, which appeared as early as the 14th century. The first watches were strictly mechanical, driven by clockwork. As technology progressed, mechanical devices, used to control the speed of the watch, were largely superseded by vibrating quartz crystals, producing accurately timed electronic pulses. The first digital electronic watch was developed in 1970.