Computer programmers developed coding systems to represent letters, numbers, and symbols with numeric codes. Three popular coding systems are EBCDIC, ASCII, and Unicode. EBCDIC used 6-bit codes and could represent 64 symbols, while ASCII is now most common and uses 8-bit codes for 256 symbols. Unicode is an developing standard that uses two bytes and 16 bits to represent each of its 65,536 symbols, allowing it to include symbols from languages around the world.