Computers have come a long way since the Sumerians first used the abacus some 2.5 millennia ago. There were several developments with mechanical devices until the British inventor Charles Babbage devised the first proper computer in 1822 that he called the ‘Difference Engine’. Although mechanical, it was correct to 31 digits, more accurate than a normal pocket calculator.

Babbage’s later ‘Analytical Engine’ was never finished, and was about 100 years ahead of its time, since it operated on a digital decimal system, using punched cards and operated by steam.  Although this might sound laughable, steam was the power source of the day, and the ‘Analytical Engine’ incorporated some of the components of modern day computers including ‘conditional control transfer capability’ that allowed commands to be executed in any order, not just that in which they are presented.

Not much happened then until Holerith successfully used punched cards in 1890 – 68 years after Babbage first proposed them.  Puched card computers were developed by International Business Machines (IBM) and Remington who at that time made typewriters among other things.

World War 2 brought the need for higher powered computers and ENIAC was born.  The Electrical Numerical Integrator and Calculator was the first electronic digital calculator and was used until 1955. It was a thousand times faster than any previous calculator, but was superseded in the 1950s with the development of magnetic core memory and the transistor.
By the 1960s RAM was increased to 64 thousand words (compare that to today) and magnetic tape was used as storage (today’s hard disk). The integrated circuit then allowed miniaturization of electrical circuits, and the modern computer was born. Circuit boards could already be printed, avoiding traditional electrical circuits, and the integrated circuit allowed computers to be brought into the home.

This also allowed the development of the Cray computer, called the biggest and fastest computer in the world, though the ILLIAC IV was in many respects faster and provided the technology for the future computer industry.  You don’t get that cheap though!

Although processing power and memory have increased tremendously since the 1970s and 80s, the technology is basically the same :  large scale integration or even very large scale integration of microcircuits, and it is believed that further development will depend upon atomic scale physics, or even integrating microcircuitry with microbiology, and the development of the microbiological system.