As early as the late 1950s, engineers at the British firm of Sumlock Comptometer Limited, a manufacturer of adding machines, imagined that electronic circuits might be used to carry out arithmetic operations in calculators that fit on a desktop. In 1961 Sumlock began to sell the Anita Mark VII and Anita Mark VIII electronic calculators, compact vacuum tube machines that could do simple arithmetic.
By 1964 several other companies were considering the electronic calculator market, using transistorized circuits rather than tubes. These included the California manufacturer of calculating machines, Friden; Japanese consumer electronics companies selling under the trade names Sony and Sharp; and the California inventor Thomas E. Osborne, whose 1964 prototype electronic calculator would influence instrument maker Hewlett-Packard’s first electronic calculator, the HP 9100 (1968). Also in 1964, the Massachusetts firm of Wang Laboratories announced its Wang LOCI, a “logarithmic calculating instrument.”
These early electronic calculators were large, heavy, expensive products, with keyboards patterned after calculating machines. The Anita, Friden, Sony, and Sharp calculators performed the four basic arithmetic operations of addition, subtraction, multiplication, and division. In 1966 Monroe International Corporation, a descendent of an American calculating machine company, introduced the Monroe EPIC 3000, an electronic calculator that not only performed basic arithmetic but took square roots. The same year a rival firm, SCM Marchant, offered calculators with and without the ability to take square roots.
The Wang LOCI, sold from1965, carried out all these operations at the touch of a key, and had further keys for finding squares, inverse squares, inverse square roots, and inverse logarithms. One form of this calculator, the LOCI II, had rough programming capabilities. Wang also soon brought out its Series 300 calculators, which were oriented toward business rather than scientific calculations. Other firms such as Sony would soon offer desktop machines that took square roots and had limited programming capabilities.
Those using adding machines had long relied on paper tapes to print out the results of calculations. The Monroe EPIC 3000 and the 1968 Friden 1150 calculators had printing mechanisms.
In the late 1960s and early 1970s, programmable desktop calculators came to have many of the capabilities of early computers, at a greatly reduced size and price. The HP9100, sold from 1968, offered a wide range of trigonometric, exponential, and hyperbolic functions. Wang responded with its 700 and 600 series calculators.