The computers of old did not use modern microchip Random Access Memory as we do today; one method of storing data temporarily was with the use of magnetic core memory. This involves tiny rings of magnetized iron threaded onto a wire mat, this was expensive to make; but it had a good access time and it is very durable as well; this type of memory is used in the Voyager probe that is currently heading outside the solar system. Travelling at 38,000 miles per hour it will be the furthest object from the Earth for a good while yet. More information here: http://codingrelic.geekhold.com/2010/07/voyager-2-soft-error.html?m=1. So the Voyager probe was not hijacked by aliens after all as some nut jobs proclaimed, merely a flipped bit caused by an energetic particle. This can not happen on the Earth; the magnetic field and atmosphere protects us from the dangerous radiation that is coming from the Sun and deep space. Another innovation in computing technology was the printed circuit board; this allowed the shrinking of circuitry by soldering the components to a board of non-conductive material with conductive tracks printed onto it that conducts electricity and connects all of the components together in one whole circuit. Then came the transistor; this is a tiny switch that was finally able to displace the old vacuum tubes.
But the old vacuum tubes were amazing devices with their warm glow; but the elements inside the tubes generated a lot of heat and therefore a massive computer built with millions of vacuum tubes would need a massive air conditioning system to keep the warehouse cool that housed it. the transistor is built upon a discovery of certain materials called semiconductors that conduct electricity in one direction only. This is like a diode; the led lights on your computer are diodes; they only shine if the DC current is flowing through them in one direction and not the other. Nowadays the circuits of computers are more densely packed than the technicians of 1970 could have dreamed; but computers built out of vacuum tubes and then the smaller and more efficient transistors are the forebears of the modern Intel Core i7 CPUs that power modern computers that can run nearly photo-realistic games and high-resolution movies that people of the 1970s could only dream of. In 1987; we were using hard disks and tape drives that could store a respectable amount of data for the size of the tape reel or hard disk platter cartridge. But the story of computing truly goes back to the invention of the Abacus and the computer that was to be built by Charles Babbage; he unsuccessfully laid plans for a mechanical computer that would be able to print accurate multiplication tables.
And I must not forget Ada Augusta, the Countess of Lovelace, the daughter of the great poet Lord Byron. She is credited with developing, the sort of programming instructions that would have been fed into the analytical engine to allow it to do the task that it was built for. She was the first ever programmer; even though her program code was never used, this is still a great achievement in history.