How do computers work? Or better phrased; How can you make a hunk of metal and stuff programmable?

From my schooldays, all a computer really is at its core is a big mess of switches, electricity goes in one end and comes out the other or gets rerouted.

You have 3 basic states:

on
off
or

I assume you have heard of binary code so will know that 010010101000101010 actually means something, this is due to each time electricity goes through a switch it tells it "yes" and that is what controls it.

This is my limited understanding, and someone else could probably expand on it greatly but this guy built the very first one...

http://german.about.com/library/blerf_zuse.htm

At the most basic level all that really controls a computer being programmable I think is the flow of electricity.

http://lmgtfy.com/?q=how+a+computer+works

Ever tried that?

Basically there's the hardware. That's the stuff inside the computer. Pretty much the engine of the computer.

Then there's the operating system. It's just a graphical interface that tells the computer what to do.

The software is programmed for the OS using a programming language. The programming language then tells what to display/do.

That's about as basic as it gets.

I mean; How can you "program" metal and electricity?

You don't. Programming is virtual. All the plastic and metal inside your computer uses electricity and has all these little dongles on them.

It's like asking how a car engine works, how the human body works, how a piano works, etc.

The CPU, as far as i understand, is just a whole load of transistors, which turn on or off depending on... well, what it's doing. The rest of the computer is build around that.

The honest answer? It's voodoo. Programming is simple to understand: you write a program in a high-level language (such as C++), which is then compiled into something your CPU (and/or operating system) can understand. The CPU then lets electricity through it at intervals depending on whether the value of each bit is 1 or 0. This, somehow, produces a meaningful result. I think it has something to do with resistors...

@redmonke: except a car engine and piano are very easy to explain, as is the human body in comparison to computers...

The human body is not simple built, the brain uses electricity too, far more advanced then the computer.
The brain is not "analog", but actually digital.
Its not possible to read a brain either, but only the nerve signals coming out can be readed. (its tried on rats)
Thats why we cant understand other animals language:
To understand another animals language, you need to know their actual language, which lies within the brain.
No one knows how the signals are decoded, just that they are electrical pulses.

Back to topic, the hardware and software work through something called kernel, which decodes the program for the hardware to read it.
The CPU process the information and shows you on the screen.
Inside the RAM chips there is flash memory where nothing gets saved, but temporarily saved when that specific program runs.
An additional gfx card will give the graphics extra MBs to save the graphic information on and it renders the information into electrical signals sent to the monitor through the cable.
The motherboard is the component that connects it all to make the signals correct transmitted and received to other parts like the CPU.

All the machine actually does, is truning electricity into information.

Adding to above, the kernel is virtual. I know that Macs have different kernels to use (vanilla is for the latest Intels and so on).

Its actually strange:
We look at light and find it entertaining, and same with specific sound-waves from the speakers.
And the speakers are built up by a strong magnet that makes electrical waves into sound.
From a silent electron to a sound wave you can hear..

The part of a computer i find the most starnge is the motherboard, a plate with electrical circuits going between the components that shape the electricity to the right type.
Its just.. strange

I accept your point about the complexity of the brain.

If you think about it, the motherboard has connections to components (RAM, CPU etc.) each of which operates at a certain voltage and amperage, so just before each component, there are resistors which provide the right voltage for the components. How this works for overclocking components, I'm not sure, perhaps potentiometers are utilised...

I'll try to bundle everyone together somewhat...

Programming language is written by someone on an already built computer. That language is sent to the CPU (Processor) with processes that language, and the end result of that is the CPU letting electricity stop and go throughout the computer, and those components interpret those electrical currents to do their job.

There is a really great Magic School Bus episode on this...

The thing is though, if you need computers to make computers work, how did they come to be in the first place

I've actually seen the first computer, it's at Bletchley Park.

I haven't seen the show in forever, but was it the one where they were in the computer and it had something to do with the kid in the wheelchair?

I learned so much from that show.