For the most part, today’s programmable controllers use RAM with battery support for application memory. Random-access memory provides an excellent means for easily creating and altering a program, as well as allowing data entry. In comparison to other memory types, RAM is a relatively fast memory. The only noticeable disadvantage of battery-supported RAM is that the battery may eventually fail, although the processor constantly monitors the status of the battery. Battery-supported RAM has proven to be sufficient for most programmable controller applications. If a battery backup is not feasible, a controller with a nonvolatile memory option (e.g., EPROM) can be used in combination with the RAM. This type of memory arrangement provides the advantages of both volatile and nonvolatile memory. Figure 5-2 shows a RAM chip.