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Fit in your pocket
There were small mechanical ones put out in the 1950s like miniature cash registers. But the first pocket elecronic ones were made by Sanyo, Canon, and Sharp in Japan in 1970
Most pocket calculators run on batteries because it is much more convenient to use in multiple places. However, some older calculators tend to run on solar power.
One can find reviews on Sharp calculators in consumer report magazines. Websites offer reviews on their own products, so you will likely find some on the Sharp website as well.
the Pocket Vibrator
he did
Casio and Sharp and Helix are the biggies
they were used to calculate difficult sums faster.
Solar power, calculators, and the double hull is what he invented
If you mean hand-held calculators, HP has sold an extensive line of them since the beginning of the hand-held pocket calculator era.
Technology advances were pocket calculators and touchtone telephones.