PLC memories can be thought of as large, two-dimensional arrays of singleunit storage cells, each storing a single piece of information in the form of 1 or 0 (i.e., the binary numbering format). Since each cell can store only one binary digit and bit is the acronym for “binary digit,” each cell is called a bit. A bit, then, is the smallest structural unit of memory. Although each bit stores information as either a 1 or a 0, the memory cells do not actually contain the numbers 1 and 0 per se. Rather, the cells use voltage charges to represent 1 and 0—the presence of a voltage charge represents a 1, the absence of a charge represents a 0. A bit is considered to be ON if the stored information is 1 (voltage present) and OFF if the stored information is 0 (voltage absent). The ON/OFF information stored in a single bit is referred to as the bit status.