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Circuits & Logic

Adafruit founder Limor Fried and virtual reality designer Nat Brown show how simple logical circuits underlie everything your computer does.

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Video transcript

(Ding) (electric guitar music) - One of the coolest things I've discovered about circuits is, circuitry can be an art form. If I have a creative idea, I can get that creative idea out using circuits. So, if you have ideas, you can use technology to make those ideas come to life. Every input or output of a computer is effectively a type of information, which can be represented by on or off electrical signals. Or one's and zero's. In order to process the information that comes in, as input, and the make the information that's output. A computer needs to modify and combine the input signals. To do this, a computer uses millions of tiny electronic components, which come together to form circuits. (upbeat music) - Let's take a closer look at how circuits can modify and process information that's represented in one's and zero's. This is an incredibly simple circuit. It takes an electrical signal, on or off, and it flips it. So, if the signal you give it is a one, the circuit gives it a zero. And if you give the circuit a zero, it gives you a one. The signal that goes in, is not the same as the signal that comes out. And so, we call the circuit, not. - More complicated circuits can take multiple signals and combine them, and give you a different result. In this example, a circuit will take two electrical signals. Now, each one might be a one or a zero. If either of the signals coming in is a zero, then the result is also a zero. This circuit will only give you a one if the first signal and the second signal are both a one. And so, we call this circuit, and. There are many small circuits like this, that perform simple, logical calculations. But connecting these circuits together, we can make more complex circuits that perform more complex calculations. For example, you can make a circuit that adds two bits together called, an adder. This circuit takes in two individual bits, each one, a one or a zero, and adds them together to calculate the sum. The sum can be zero plus zero equals zero, zero plus one equals one, or one plus one equals two. You need two wires coming out because it can take up to two binary digits to represent the sum. Once you have a single adder for adding two bits of information, you can put together multiples of these adder circuits side by side to add together much larger numbers. - For example, here's how an eight bit adder adds the numbers 25 and 50. Each number is represented using eight bits resulting in 16 different electrical signals that go into the circuit. The circuit for an eight bit adder has lots of little adders inside of it, which together, calculate the sum. Different electrical circuits can perform other simple calculations like subtraction or multiplication. In fact, all the information processing your computer does it's just lots and lots of small simple operations put together. Each individual operation done by a computer is so, so simple, it could be done by a human. But these circuits inside computers are way, way faster. - Back in the day, these circuits were big and clunky. An an eight bit adder could be as big as a fridge and it would take minutes for them to perform a simple calculation. Today, computer circuits are microscopic in size and way, way faster. Why are smaller computers also faster? - Well, because the smaller the circuit is, the less distance the electrical signal has to go. Electricity moves at just about the speed of light which is why modern circuits can perform billions of calculations per second. - So, whether you're playing a game, recording a video, or exploring the cosmos, everything you can possibly do with technology requires lots of information to be processed extremely quickly. Underneath all this complexity, is just lots of teeny little circuits that turn binary signals into websites and videos, music and games. These circuits can even help us decode DNA to diagnose and cure disease. (upbeat music)