ENIAC:

      - ENIAC stands for Electrical Numerical Integrator and Computer.

- ENIAC, was the first general purpose electronic computer.

- The ENIAC was big it was, 30 tons and took up 1800 square feet of floor space. The ENIAC contained 6000 manual switches.

- The ENIAC was designed and built to calculate artillery firing tables for the U.S Army’s Ballistic Research Laboratory.

 Vacuum Tube Sizes:

- In electronics, a vacuum tube is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space.

- Some special function vacuum tubes are filled with low-pressure gas: these are so-called soft valves (or tubes), as distinct from the hard vacuum type which have the internal gas pressure reduced as far as possible

- Almost all depend on the thermal emission of electrons, hence thermionic.

- The first generation computers were huge, slow, expensive, and often undependable.

- In 1946 two Americans, Presper Eckert, and John Mauchly built the ENIAC electronic computer which used vacuum tubes instead of the mechanical switches of the Mark I.

- The ENIAC used thousands of vacuum tubes, which took up a lot of space and gave off a great deal of heat just like light bulbs do.

- The ENIAC led to other vacuum tube type computers like the EDVAC (Electronic Discrete Variable Automatic Computer) and the UNIVAC I (UNIVersal Automatic Computer).

- The vacuum tube was an extremely important step in the advancement of computers.

- Vacuum tubes were invented the same time the light bulb was invented by Thomas Edison and worked very similar to light bulbs.  Its purpose was to act like an amplifier and a switch.

Transistor:

- A transistor is a semiconductor device commonly used to amplify or switch electronic signals. - A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit.

- A voltage or current applied to one pair of the transistor’s terminals changes the current flowing through another pair of terminals. Because the controlled power can be much larger than the controlling power, the transistor provides amplification of a signal.

- In 1947 three scientists, John Bardeen, William Shockley, and Walter Brattain working at AT&T’s Bell Labs invented what would replace the vacuum tube forever.

- This invention was the transistor which functions like a vacuum tube in that it can be used to relay and switch electronic signals.

- There were obvious differences between the transistor and the vacuum tube.  The transistor was faster, more reliable, smaller, and much cheaper to build than a vacuum tube.  One transistor replaced the equivalent of 40 vacuum tubes.

- They were also much smaller and gave off virtually no heat compared to vacuum tubes.

IC (Integrated Circuit):

- The integrated circuit was independently co-invented by Jack Kilby of Texas Instruments^[2] and Robert Noyce of Fairchild Semiconductor ^[3] around the same time.

- Kilby recorded his initial ideas concerning the integrated circuit in July 1958 and successfully demonstrated the first working integrated circuit on September 12, 1958.^[2]Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit.^[4]

- Robert Noyce also came up with his own idea of integrated circuit, half a year later than Kilby

- Placing such large numbers of transistors on a single chip vastly increased the power of a single computer and lowered its cost considerably.

Timex Sinclair:

- The keyboard is a ‘touch sensitive membrane’, a flexible plastic surface with the actual switches under the surface.

- While easy to clean and water resistant, it is very difficult and slow to type on, because you have to press hard and very deliberately to use the tiny, closely-spaced keys. Touch-typing is impossible.

- Resourceful users hacked into their system and added their own ‘real’ keyboard, external to the system.

 First Home Computer:

 - In 1936, Zuse made a mechanical calculator called the Z1, the first binary computer.

- Zuse used it to explore several groundbreaking technologies in calculator development: floating-point arithmetic, high-capacity memory and modules or relays operating on the yes/no principle. Zuse’s ideas, not fully implemented in the Z1, succeeded more with each Z prototype.

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