Binary, bits and bytes

A bit is one binary digit, a single 0 or a single 1. A pattern such as 1011 has four bits, and 1000111 has seven. Bits are joined into bigger units. A byte is 8 bits, the unit in which a computer usually stores one symbol: in a simple code one byte is enough for one letter, one digit or one sign (other codes, for example for Arabic letters, may need two bytes for one letter). Bigger sizes are built from bytes. In this course 1 kilobyte (1 KB) is 1024 bytes; some books use 1000, so always check which one is meant. Bits and bytes measure how much data there is, not how fast it moves. To change units, multiply: bytes × 8 gives bits, and KB × 1024 gives bytes.