The difference between digital and analogic forms is exemplified in the two different types of watches and clocks now available. A digital watch presents the time in discrete units. It is either 12:57 or 12:58 (or some discrete unit in between, such as 12:57 and 10 seconds as opposed to 12:57 and 11 seconds). With the analogic watch, however, time is continuous. A person who sees the time as "12:57 and 10 seconds" on a digital watch, may see the time as "about one o'clock" on an analogic watch. A similar difference exists between a digital calculator and the analogic slide rule. The slide rule is excellent for making "approximations," but it cannot yield precise digital data.