Aspies For Freedom

if you drag your selection around something that has a white background (imagine lets say homer simpson on a white background, and you select around him) and go to *Cut* when you go to *paste* again you will be able to choose the transparency tool, when selected, homer won't be on a white background anymore, the background will be transparent, so you could then paste him onto another picture, say, a background of a beach? and he wouldnt have a white square around him where you cut him out...he'd just perfectly paste onto the background as if he was there x

Essentially anything that could be an alterable switch can be used to make a computer. The earlier computers like the UNIVAC used vacuum tubes to do this - each switch could be set to allow air through or not allow air through a tube by means of vacuum sealing (i.e. they could be set to "on" or "off"). Once all the switches are set, another burst of air through the right channels is used as the "input", and where the air comes out is considered the "output". The output can then be put through a new set of switches as new input, enabling complex calculations.

Essentially you could make a computer out of anything that let you "set" switches - like water streams, wooden balls rolling down ramps, etc...

Modern computers use transistors to do the same thing - a transistor has two electrical paths going through it, and running an electrical current through one path allows electricity to flow through the other. A silicon chip is millions of very small transistors linked together.

As an interesting side-note, the phrase "a bug in the system" comes from the old vacuum tube computers - sometimes insects and other "bugs" would get stuck in the vacuum tubes, stopping them from sealing properly, and causing errors in calculations.

There's only 10 types of people in the world - those who know binary, and those who don't. *grins*

Right.
As an electrical engineer, I feel compelled to further clarify the clarification.

Go to a flea market and you might find some vacuum tubes, either in bulk or inside old radios from the 1960s or prior.  The transistor was invented at Bell Labs in 1947, but didn't gain widespread use until the 1960s.  Anyway, the tubes are usually little glass bulbs filled with small metal parts.  

There's lots of different kinds of tubes.  The simplest is a diode which lets electrical current flow through it only in one direction.  One step above that is the triode which can be used for tuning, oscillating, amplifying, or in the case of computers, switching.

The triode is called such because it has three main parts: cathode in the center, surrounded by a wire grid, surrounded by an anode plate.  It is a fundamental property of physics that if you heat an object, it will emit electrons.  If you heat a specially coated metal cathode in a vacuum tube and apply a high negative voltage to it in reference to the anode, the cathode will emit a great many electrons.  Think about a 400 volt battery with the negative terminal on the cathode and the positive on the anode.  The cathode is commonly a narrow metal tube that contains a filament.  This is similar to the filament in a toaster, but uses a separate low voltage power supply.  The great number of electrons supplied by the battery are able to flow freely through space in the tube because it is a vacuum inside.  The are emitted by the hot cathode and attracted by the positive charge on the anode, so that is where they go.

The only thing to stop the electrons from reaching the anode is the grid which is a long spiral of thin, widely spaced wire.  Put on the grid a negative voltage with respect to the cathode, very few electrons will reach the anode.  Put a positive voltage on the grid and many electrons will reach the anode.  Changing the grid voltage, either very negative or very positive, gives us very little or very much electron current flowing from cathode to anode.  Thus we have a binary signal on which to base a computer that occupies the space of a large room and serves as the building's ventilation heat source during winter.