The basic mathematical functions performed by most PLC's are: add, subtract, multiply and divide.These types of instructions are used by PLC's to gather data from various memory locations, to compare data, and to scale values.

Data comparison is an extremely useful programming tool that allows outputs to be energized depending on wether data in one memory location is greater than, less than, or equal to data stored in another memory location. Scaling is also an important application of math function because it allows numbers which are very small or large to be elarged or reduced by a fixed constant.

The standard format for math functions in many PLC's is is that the desired math operation is performed on a memory location, and not directly on a number. In other words, if you wish to add two numbers, these numbers must be entered into memory locations, and the contents of the addresses will be added together.