A code book turns answers into numbers, and computers store every value as bits, each 0 or 1; a byte is 8 bits. The same bits can mean different things in different contexts. In binary, each place value is 2 raised to the power of its position, counting from 0 at the right, and a fixed number of bits limits the range of numbers, which can cause an overflow error. Compression reduces the number of bits: lossless compression rebuilds the original exactly, and lossy compression rebuilds only an approximation. Where data are stored affects speed, reliability, accessibility, privacy and integrity.