The word length corresponds to the number of digital states and is determined in computers by the central processing unit( CPU) and the memory architecture. Thus, in older computers data words with a word length of 4 bits and 8 bits could be processed, later there were central processing units with bus widths of 16 bits, 32 bits and 64 bits and data word lengths of 2 bytes, 4 bytes or 8 bytes.
A distinction is made between data words with fixed and variable word lengths. Data words with variable word lengths are identified by start and end characters. One speaks of a command word if a memory word contains a command.