As well as being able to write logic expressions using
mathematical notation, we can also draw* logic circuits*. These are sort
of like an electrical diagram, which you can follow along by hand from one side
to the other. There are three main symbols you need to know. They are often
called ‘gates’.

### NOT symbol

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This looks like a triangle with a small circle at the tip. When you put a statement like ‘x’ into it, you come out with the opposite of that statement. So true becomes false, and false becomes true. Notice that there’s only one input.

### OR symbol

This is like a triangle but with *all* the sides
curved. Also notice how it has *two* inputs. You can actually have more
than two inputs as well, for instance, if you have x, y and z as inputs then it
would look like this:

### AND symbol

The AND symbol is like a bit of a rectangle with a semicircle attached to one end. It can also have more than 2 inputs, like in this particular case.