By 1980, TI made the slide rule obsolete with hand held scientific calculators.
:D
I beg to differ, both by date and company. In February of 1972, Hewlett-Packard (HP) introduced the HP-35 ($395), the first practical, general production, hand-held, scientific calculator. In November of that same year, Texas Instruments (TI) introduced its SR10 ($149) "Slide Rule" Calculator. In 1975, the Keuffel and Esser company ceased its manufacture of its formerly very popular Deci-Lon lines, the ten-inch "regular" (Deci-Lon 10) and five-inch "pocket" (Deci-Lon 5).
My first calculator was a $100+ 4-banger brick of un-recallable name but I moved to the first HP-25 in '75 and updated as new models came along until my last and still best HP-200LX. I still use this jewel on a frequent basis even though I have an iPod Touch and other gadgets. It had the near-ultimate PIM (Personal Information Manager) that I have yet to see the equal let alone superior.
[Sorry TI fans, I could not resist. And for the HP Management IDIOTS who bowed to Microsoft and killed the great HP Calculator Division, eternal shame!]