If you need an illustration of the accelerating speed of technological change, look no further than the electronic calculator, that modest little device that does the most complex sum instantly and that you hold in the palm of your hand.
Or more likely don’t any more… for the pocket calculator, which took more than four millennia to evolve and only reached its current form in the 1990s, is already obsolescent, if not actually obsolete.

It had taken 3,700 years to move from the abacus to the first mechanical calculators and a further 250 years for mechanics to give way to electronics. Yet it would take barely a decade for the calculator to make its third metamorphosis, from a heavy, bulky, expensive desktop machine that needed AC mains power to a cheap and compact battery or solar-powered device that would slip into a pocket or wallet.
To make that transition, engineers had to solve three huge principal challenges: replacing boards of transistors with integrated microchips, designing less power-hungry electronics and displays that could run on batteries and developing slimmer, simpler control mechanisms.
Texas Instruments prototype ‘Cal-Tech’ prototype of 1967 with its compact form was a prophet of the future, but it still used transistors and needed mains power.
However, within the next thee years, calculator development became the leading edge of Large Scale Integration (LSI) semiconductor development, with strategic alliances formed between the mostly Japanese calculator manufacturers and the largely U.S. semiconductor companies. Thus Canon teamed with Texas Instruments, Hayakawa Electric (Sharp Corporation) with North-American Rockwell, Busicom with Mostek and Intel, and General Instrument with Sanyo.
By 1969, a calculator could be made using just a few low power consumption chips, allowing the size and power consumption to be drastically reduced. Yet even as they were introduced, these calculators were already obsolete as well as being too expensive for most consumers.
Within a year, Sinclair had produced the Cambridge as the first low-cost calculator, priced at £29.95 (or £24.95 in kit form). The Sinclair calculators cost far less than the competition, but had an ugly bulge in the back for the PP9v battery and with a design that frequently led to errors when doing compound sums. Hewlett Packard and Texas followed suit with machines capable of complex mathematics. During the ‘Calculator Wars’ of the mid-1970s, most of the specialist and ‘me, too’ manufacturers disappeared, leaving a market dominated by five major brands: Sharp, Texas, HP, Canon and the new kid on the block, Casio. The end result, by 1978, was a new generation of pocket calculators with power consumption so low that they could be driven by solar cells. By 1980, pocket and desktop calculators had essentially reached the forms we recognise today; compact in form, using single chips and LCD displays, operated via silicone membrane or dome switch keyboards, powered by solar cells or button batteries and capable of a wide range of functions. Pocket calculators had also become very cheap, with some selling for as little as $1.99. Before long, companies were starting to give pocket calculators away as freebies, much as USB memory sticks are today.
As the 80s gave way to the 1990s, new threats emerged to the calculator, the smart phone and PDA’s. Four main factors are keeping the calculator alive. One is that designs have been successively optimised to purpose, producing a level of function and capability that even tailored apps struggle to emulate. The second is the high price of current smartphones and tablets while the third is that some people just find it easier, quicker and more precise to operate a physical device than a touchscreen.
Last, and arguably most important, ‘dumb’ calculators have over the decades earned a place in school and university exam rooms that remains closed off to ‘smart‘ tablets and phones for the foreseeable future.

The full history of calculators is really quite phenomenal and surprisingly interesting,and this site is where I got the information from :-

wwwthecalculatorsite.com  

This one is my old and trusted basic add’emup and I still like it better than the smart phone app. 🙂