Slide rule
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A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for conducting mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonome
Typical ten-inch (25 cm) student slide rule (Pickett N902-T simplex trig)
Cursor on a slide rule
This slide rule is positioned to yield several values: From C scale to D scale (multiply by 2), from D scale to C scale (divide by 2), A and B scales (multiply and divide by 4), A and D scales (squares and square roots).
A normal-sized slide rule sitting inside a 7-foot (2.1 m) teaching model
HP-35
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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. It was introduced in 1972.
Slide rule
…its use to continue to grow through the 1950s and 1960s even with the introduction of mainframe digital electronic computers. But after the handheld HP-35 scientific calculator was introduced in 1972 and became inexpensive in the mid-1970s, slide rules became largely obsolete and no longer were in use by…
HP-35 (1st version) scientific electronic pocket calculator
HP-35 mainboard