History of computing

Early computing

The earliest device used for computing was the Abacus which makes calculations easier by having beads in rows, each representing a different power of 10

Charles Babbage theorized the analytical engine, a mechanical computer that would not be restricted to one type of computation. Therefore he’s sometimes credited as the father of computing.

This inspired further scientists like Ada Lovelace which is considered the first programmer.

One of the first computers to use electrical parts and punch cards was Herman Hollerith's tabulating machine to help count the 1890 american census. The punched out hole allowed quicksilver to close an electrical circuit, actuating an electrical motor to turn the wheels. Hollerith would found his own company which would later become International business machines (IBM).

Electronic computers

Harvard mark 2

One of the biggest electromechanical computers ever was the Harvard Mark 2, mainly used for computations in the Manhattan project. It used mechanical relays and 765.000 components. It used a 50 ft shaft powered by a 5 hp engine to synchronize all parts.

Because of the physical mass of the relay arm, the speed of it is limited, with the quickest relays doing about 50 switches per second. The Harvard Mark 2 was also the first computer to have a “bug”, a dead moth that jammed one of the mechanical parts.

Mark 1

Vacuum tube

One of the first vacuum tubes was called the thermionic valve. It houses 2 electrodes in a vacuum tube and used thermionic emission. One electrode could be heated and would emit electrodes which would be attracted by the other electrode but only if it was positively charged. In this case, a current would flow from one electrode to the other.

In 1906, Lee de Forest would add a third electrode which would act as a switch between the two transmitting / receiving pair. This Triode vacuum tube would become hugely succesful as it would be the first electrical switch without moving mechanical parts.

Electrical computers

This marked the switch from electromechanical to electrical computing. The colossus mark 1 was the first fully functional and programmable electrical computer containing 1600 vacuum tubes. 10 of them were built to decipher Nazi code during the second world war.

This was a massive improvement but the types of calculations were still limited. The first general purpose, programmable, electronic computer would then be the ENIAC at the university of Pennsylvania.

Colossus mark I

ENIAC

The transistor

In 1947 it was invented at Bell laboratories by three US physicists: John Bardeen (1908–1991), Walter Brattain (1902–1987), and William Shockley (1910–1989). It used semiconductors and was able to switch more than 10.000 times per second. Mainly, transistors were sturdy, not using fragile materials like glass and could therefore almost immediately be miniaturized. In 1957, the first fully transistor powered, commercially available computer came out, containing around 3000 transistors.

Logic levels

Read A majority of systems we use rely on either 3.3V or 5 V TTL Levels. TTL is an acronym for Transistor-Transistor Logic. It relies on circuits built from bipolar transistors to achieve switching and maintain logic states. Transistors are basically fancy-speak for electrically controlled switches. For any logic family, there are a number of threshold voltage levels to know. Below is an example for standard 5V/3,3V TTL levels:

VOH -- Minimum OUTPUT Voltage level a TTL device will provide for a HIGH signal (2,7 V/2,4V)

VIH -- Minimum INPUT Voltage level to be considered a HIGH (2 V/2V)

VOL -- Maximum OUTPUT Voltage level a device will provide for a LOW signal (0,4 V/0,5V)

VIL -- Maximum INPUT Voltage level to still be considered a LOW (0,8 V/0,8)

Therefore, every voltage in between 0,8 V and 2 V is considered invalid. This also shows that 5V and 3,3 V TTLs are compatible, though the higher voltage may damage the 3,3V parts so a voltage divider might be necessary.

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