The HP-35 was Hewlett-Packard's first pocket calculator and the world's first scientific pocket calculator (a calculator with trigonometric and exponential functions). Like some of HP's desktop calculators it used reverse Polish notation. Introduced at US$395, the HP-35 was available from 1972 to 1975. Market studies at the time had shown no market for pocket sized calculators. In about 1970, HP co-founder Bill Hewlett challenged his co-workers to create a "shirt-pocket sized HP-9100". Thus, th… (More on Hp-35)