Link to site B of this episode’s course
Table of contents
1. Electromechanical Computer
At the beginning of the 20th century, early computing devices were aimed at specific purposes. With the rapid growth of population, the closeness of trade, the advancement of science, and various complex situations, the amount of data increased dramatically, and people needed stronger and more automatic computing capabilities.
Computers became bigger and bigger, and soon they changed from the size of a cabinet to the size of a room. One of the largest electromechanical computers was the Harvard Mark I, designed by Howard Aiken (built by IBM) and completed in 1994. One of the earliest uses of this machine was to run simulations for the Manhattan Project (a plan to develop an atomic bomb using nuclear fission reactions). The picture below is the Mark I image.
I feel a sense of familiarity when I see this place. I wonder if Iron Man’s father, Howard Stark, and Mark 1 paid homage to this place, including Howard Stark who happened to be during World War II (I guess).
The brain of this machine is the relay, which turns the controlled output circuit on or off when the input current reaches a specified value.
The relay can be connected to a motor or other circuit. If the circuit is turned on, the motor will increase the counting gear by 1, just like the tabulating machine mentioned above. In 1940, a good relay could flip 50 times in 1 second, but it still could not meet the needs of complex problems. Havermark No. 1 can do three additions or subtractions in 1 second, one multiplication in 6 seconds, and one division in 15 seconds. More complex trigonometric functions may take more than 1 minute. Add to this the problem of gear wear, and the increased probability of failure as the number of relays increases, and people start looking for something faster and more reliable to replace the relays.
Do you know where the computer term "Bug" comes from? In September 1947, a Harvard Mark II operator pulled a dead bug from a faulty relay. Grace Hopper said, "From then on, when anything went wrong with a computer, we said it had bugs in it." This is it. The source of the "bug".
2. Electronic computers
By 1904, John Ambrose Fleming developed the thermionic tube, which contained two electrodes in an airtight glass bulb. This was the world's first vacuum tube. One of the electrodes can be heated, emitting electrons (thermionic emission), and the other electrode attracts electrons, creating an electric current.
Lee de Forest added a third control electrode between the two electrodes designed by Fleming. Applying a positive charge to the control electrode will allow electrons to flow, but if a negative charge is applied, it will prevent the flow of electrons, so through the control circuit , can open or close a circuit, the same function as a relay, but importantly, there are no moving components in the vacuum tube, which means less wear and tear, and more importantly, it can open and close thousands of times per second.
Thus these "triode vacuum tubes" became the basis of radios, long-distance telephones, and other electronic devices for nearly half a century. It would be perfect if...if it didn't burn out like a light bulb! But its emergence is still a huge improvement.
This blog post introduces this history in detail, and interested friends can browse it. How does a vacuum triode work? A brief discussion on the origin of vacuum triodes - Analog Technology - Electronic Enthusiast Network How do vacuum triodes work? A brief talk about the origin of vacuum triodes - most people started using semiconductors and used so-called crystal combinations as rectifiers. 
https://www.elecfans.com/analog/202302212014247.html By 1940, its cost and reliability had improved and it could be used in computers, which marked the shift from electromechanical to electronic computers. The first large-scale computer to use vacuum tubes was the Colossus MK 1, designed by engineer Tommy Flowers and completed in December 1943. Titan 1 was used at "Bletchley Park" in England to crack Nazi communications. Titan is considered the first programmable electronic computer.
Two years ago, Alan Turing, the father of computer science, also built an electromechanical device "Bombe" in "Bletchley Park" to crack the Nazi "English code" communication encryption equipment. The movie "The Imitation Game" is adapted from this period of history.
ENIAC (Enter the The Electronic Numerical Integrator and Calculator), developed in 1946 by John Mauchly and J. Presper Eckert of the University of Pennsylvania, is the world's first truly general-purpose, programmable, electronic computer. ENIAC can execute 5,000 times per second. Addition and subtraction of tens digits. It has been in operation for ten years, and it is estimated that it has completed more calculations than all mankind combined.
To further reduce cost and size while increasing reliability and speed, a new electronic switch is needed. In 1947, Bell Labs scientists John Bardeen, Walter Brattain, and William Shockley invented the transistor, and a new computer era was born! The physics of transistors is quite complex and involves quantum mechanics. The conductivity of a semiconductor material can be controlled to allow or disallow the flow of electrical current.
The first transistor could switch on and off 10,000 times per second, a huge increase in speed. And, unlike vacuum tubes, which are made of glass and can be fragile, transistors are solid state. In terms of volume, transistors can be much smaller than relays or vacuum tubes, which provides the basis for the production of smaller and cheaper computers.
The IBM 608, released in 1957, was the first computer to be entirely made of transistors and available to consumers. It has 3,000 transistors and performs 4,500 additions or around 80 multiplications and divisions per second. Today, transistors in computers are smaller than 50 nanometers. Not only are transistors small, they are also super fast, switching millions of times per second and operating for decades. Many transistors and semiconductors were developed in the "Santa Clara Valley", and the most common material used to produce semiconductors is "silicon", so this area is called "Silicon Valley".
That’s all the content in this episode of the course!
