# What is a Computer? (Part 2)

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So now that we have the capability of computing values without human error, once we have that ability, the next important part of the computer is to accept variable input from the user. And as I mentioned before, it’s not just the fact that we can input numbers into the computer. But, what if we could actually reprogram the device? Right? What if we could enable certain features or certain abilities of that computer by just pushing the input?

Can anyone guess what mechanical device was the first one to accept variable input from a user? It was the Jacquard loom. Not a whole lot of people know about the Jacquard loom, but it was invented in 1801 by Joseph Marie Jacquard, who basically simplified the process of manufacturing textiles. Particularly with textiles that have really complex or shifting patterns or even rounded designs and things of that nature. The Jacquard loom used a series of punch cards to control the thread. While this doesn’t actually perform any calculations, it is very important as this is the first example of a machine responding to different input or programs in the form of punch cards. Now, the car loom wasn’t the first thing that ever used the idea of punch cards. There was a few things before its time, but there’s Jacquard loom was one of the first one that truly automated the process. Although there were still some manual aspects of the Jacquard loom, the majority of it was completely automated.

The Difference Engine wasn’t the only computer designed by Babbage. The Analytical Engine, which was Babbage’s true dream: a general purpose computer. Had it been built as Babbage envisioned, it would have been one of the first true modern computers. He previously worked on design of an analytical engine, which was a true multi purpose computer. It would have been composed of several different parts that each performed different functions, allowing it to do many different kinds of calculations, be reprogrammed, store information and all sorts of different things. This was one of the first steps that we have seen, be developing or to developing a true modern multi purpose computer. Analytical Engine used a set of input cards called punch cards to determine what calculations to do and what numbers to use. And so this was greatly inspired by the Jacquard loom. This is very similar to how programs on today’s computers are structured: with a list of instructions on the program or in the program and the data that’s provided by the user.

Borrowing that idea from the Jacquard loom, the analytical engine was able to use a system of punch cards to accept input and determine the calculations that needed to be done. Babbage’s son remarked once that the Analytical Engine could calculate almost anything, it is only a question of the cards and time. So how many cards it would require and the amount of time it would take to actually operate, speculating that 20,000 cards would not be out of the question. It was a pretty impressive physical mechanical machine. This is very much like how modern computers worked, and even in the 40s and 50s a lot of computers worked off of this punch card system.

In the Analytical Engine, there is also the mill. The mill is really the heart of the machine. I was equate this closer to what a modern CPU was. In order to handle the computation done by the machine, Babbage designed this part that was capable of performing all of the basic numerical calculations. This used many of the breakthroughs that Pascal and Leibniz had some 200 years earlier. And so here in this picture on the slide is a very small picture of one part of the mill, which was constructed actually by Babbage’s son in 1910 to show that it was actually possible. The mill is able to perform all the basic arithmetic operations like addition, subtraction, multiplication, division, as well as calculate the square roots of numbers. This is really the first true step towards a modern CPU, which is really exciting. With those two parts in place, the next big hurdle was the ability to store data and output the results.

The store was Babbage’s true innovation. The store, which would have been a bank of columns capable of storing up to 1000 numbers up to 40 decimal places each. So that’s pretty high precision for a mechanical device. This was equated to roughly 16 to 17 kilobytes of modern day storage if you want to look at it that way, so quite a bit. Now, while the store was never actually built for the Analytical Engine, much of the design for the store was incorporated into his Difference Engine number two design, which is shown here in this picture. This represents the first time that calculated values could be stored directly in the machine, and recalled at a later time as required by the program.

The last thing that our computer should be able to do is output results. Charles Babbage also thought of this, right. As we saw in the video, in our previous lecture, Babbage also designed a printer that would output the results of calculations, not only onto paper, but directly into a plaster panel that could be used to create printing plates. You can imagine using this device to maybe make all of those tables in the back of your mathematic textbook. Which were a pain to do by hand, but now we could have a machine that would actually do the math and print it as well.

Now what those parts in place the stage is really now set for the coming computer revolution. Unfortunately, it will take an entire world consumed by war before the next major step in the history of computing was made. And we’ll pick that story up in the next couple of lectures.

This really leads us back to Charles Babbage, the father the modern day computer, it’s really quite mind boggling to see the Difference Engine, Analytical Engine, the Difference Engine number two, really all of which you only completed a simple prototype during his lifetime. And the fact that he was able to create these devices completely theoretically on paper, and they worked as intended exactly how he designed them is really, really quite amazing. Charles Babbage is known as the father of modern day computer because of these devices that were really truly one of the first examples of a general purpose computer. But if you’re interested in learning more about Charles Babbage, you can read his autobiography titled, “The Passages from the Life of a Philosopher” which is free and available online.