Binary, bits and bytes

Computers store everything as bits, ones and zeros. Bits are grouped into bytes of 8 bits, so a byte has 256 possible values, 0 to 255. Binary is counting in base 2, where each place is worth double the one to its right.

So 1011 is 8 + 0 + 2 + 1 = 11. Hexadecimal, or base 16, is a shorthand for binary, because each hex digit is exactly 4 bits. That is why colours look like #FF8800 and memory addresses look like 0x7ffe.

Learn to convert small numbers between decimal, binary and hex by hand. The point is not arithmetic for its own sake. The same bits can mean a number, a letter or a pixel, depending on how a program reads them, and that idea runs through the rest of this stage.