http://xkcd.com/505/

George Gough

[Edit]
Can't forget my trusty signature huh?

Still forgot it!

You make them.

George Gough

It involves boolean statements, binary, and transistors. Given the question, explaining exactly how it works is probably going to confuse you, but note that the first programs were written in binary and hexadecimal, nothing more.

I'm well aware of both, but didn't include them for a specific reason: The analytical engine was never actually constructed. Ada Lovelace was the first programmer, but her programs were never executed.

All computer CPUs are setup to perform different operations when different instructions are presented to them, which is the machine language of the computer. The first programmers worked with machine language directly.

Eventually programmers discovered that they could write a program in machine code that could interpret text and convert it to machine language. That text was in the form of assembly language, which varies from computer to computer because different computers have different forms of machine language. Assembly is really just a more readable form of machine language, but it's considered a second-generation language because it's a step up from machine code.

Using assembly, programmers discovered they could parse more complex constructs that were easier to read, and they could design languages that had true structure. C is one of the best examples of an early third-generation language. Code written in C is converted into the machine code for whatever system it is compiled for.

In the beginning, for and while loops didn't exist--such things are really just constructs within languages like C, Pascal, BASIC, etc. At the raw end of things, pure machine code, the only way to do looping is with a jump instruction (i.e., a goto) or a conditional jump. A C compiler knows that when you use a while() loop, internally it should look like this:

(start of loop)
test condition
if false, goto end of loop
do stuff inside loop
goto start of loop
(end of loop)

So C is just taking a format you can easily read and converting it to one that the computer understands. The very first programmers, though, didn't have that luxury and had to do it all at the very low computer level.

Lummox JR

Rushnut wrote:

But here is where im lost!
How could the computer understand this?! How could a big box of microchips and drivers, with absoloutly NOTHING on them, understand, ANYTHING?

Computers don't understand, as such; they just do what they're told. A CPU knows that when a "high" voltage is applied to some input pins and a "low" is applied to others, it has been given a certain instruction based on the pattern of high and low values. That instruction is basically run through a massive number of transistors that signal other parts of the CPU to hold a given voltage or release it onto outgoing wires into still other parts of the CPU. The computer is controlled by an internal clock that tells it when to execute the next step of its instructions. It is essentially just a complex step up from a mechanical clock.

Lummox JR

Consider that I've built a see-saw out of wood. On one end of the see-saw is a cup into which I can drop marbles.

If I drop one marble into the cup then that end of the see-saw will go down, and the other end will come up. As that end swings up, it may hit a marble on a ledge somewhere, causing that marble to fall into a cup somewhere else. This only happens if there is a marble on that ledge, though. If there isn't a marble on that ledge then nothing happens. As the other end continues to fall down under the weight of the marble, eventually the marble is dumped out and falls to the floor (or perhaps into another cup). The see-saw then returns to its original position.

If I drop two marbles into the cup, then the arm swings faster, and it moves further before both marbles are dropped. Now the other arm not only pushes off any marbles sitting on the first ledge, but it may even go higher and push off marbles sitting on the ledge above it. These marbles fall into other cups, or fall onto ledges to wait for an arm to swing around and hit them.

This may seem extemely contrived, but wooden 'computers' have actually been built using wooden dowels and marbles. I can't seem to find the correct Google search to turn up the images of said computers, though.

The next step up from wood is the gears and such that have been mentioned before. After those came mechanical relays, vacuum tubes, and all sorts of interesting analog mechanical devices. Transistors, what computers are based on now, are no different, fundamentally, from those see-saws and marbles, though. The important difference is that transistors are really really small, small enough that we can fit billions of them into a chip - making a modern computer with billions of marbles and dowels just isn't logistically possible.

But transistors really are the same thing. A transistor is a mechanical device which, in concert with other transistor and assorted electrical devices, performs mechanical calculation. Instead of using levers and marbles, they just use electrons and really tiny bits of silicone.

Oh. And Magic/More Magic.

I know that it isn't the computer that you were looking for, but you reminded me of this.

First Computer