of an atomic bomb. Decline The importance of the slide rule began to diminish as electronic computers, a new but rare resource in the 1950s, became more widely available to technical workers during the 1960s. Another step away from slide rules was the introduction of relatively inexpensive electronic desktop scientific calculators. The first included the Wang Laboratories LOCI-2, introduced in 1965, which used logarithms for multiplication and division; and the Hewlett-Packard HP 9100A, introduced in 1968. Both of these were programmable and provided exponential and logarithmic functions; the HP had trigonometric functions (sine, cosine, and tangent) and hyperbolic trigonometric functions as well. The HP used the CORDIC (coordinate rotation digital computer) algorithm, which allows for calculation of trigonometric functions using only shift and add operations. This method facilitated the development of ever smaller scientific calculators. As with mainframe computing, the availability of these machines did not significantly affect the ubiquitous use of the slide rule until cheap hand-held scientific electronic calculators became available in the mid-1970s, at which point it rapidly declined. The pocket-sized Hewlett-Packard HP-35 scientific calculator was the first handheld device of its type, but it cost US$395 in 1972. This was justifiable for some engineering professionals, but too expensive for most students. Around 1974 the handheld electronic scientific calculator made slide rules largely obsolete. By 1975, basic four-function electronic calculators could be purchased for less than $50, and by 1976 the TI-30 scientific calculator was sold for less than $25 ($ adjusted for inflation). 1980 was the final year in Texas school U.I.L. competition to use slide rule contest. The University Interscholastic League was organized in 1910. Originally the U.I.L. was formed to administer literary events, but became the governing body of school sports events as well. Comparison to electronic digital calculators Even during their heyday, slide rules never caught on with the general public. Addition and subtraction are not well-supported operations on slide rules and doing a calculation on a slide rule tends to be slower than on a calculator. This led engineers to use mathematical equations that favored operations that were easy on a slide rule over more accurate but complex functions; these approximations could lead to inaccuracies and mistakes. On the other hand, the spatial, manual operation of slide rules cultivates in the user an intuition for numerical relationships and scale that people who have used only digital calculators often lack. A slide rule