A pocket calculator is a small, often battery-powered electronic digital computer made possible by integrated circuit and semiconductor technology. Typically they are limited to a single-number display and a few basic functions of artihmetic, but some modern ones have more of the features of a general-purpose computer.
The first hand-held, as opposed to desktop calculators, went on sale in 1970 with models from Sharp and Canon, weighing around 1.7 lb. The first pocket-sized model came out in 1971 from Bowmar, with four functions and an eight-character red LED display, for $240. The first with scientific functions was the 1972 HP-35, but the most common early scientific calculator was the TI-30 from Texas Instruments.
Pocket calculators rendered the Slide Rule obsolete.