The third and final structural information unit used within a PLC is a word. In general, a word is the unit that the processor uses when data is to be operated on or instructions are to be performed. Like a byte, a word is also a fixed group of bits that varies according to the controller; however, words are usually one byte or more in length. For example, a 16-bit word consists of two bytes. Typical word lengths used in PLCs are 8, 16, and 32 bits. Figure 5-4 illustrates the structural units of a typical programmable controller memory