# About expressions

An expression can be a tag name, a tag placeholder, a mathematical or logical equation, or a function that returns a numeric, string, or true or false value. For expressions that return true and false values, 1 and other non-zero values signify True, and zero signifies False. Expressions let you manipulate the data gathered from devices and make it more meaningful by comparing it to other values, combining it with other values, creating cause and effect relationships between values, or displaying it.

Expressions can contain:

- Tags, tag placeholders, arithmetic, and bitwise operators, and mathematical functions such as SQRT (square root), that return numeric values.
- Relational and logical operators, and functions such as ALM_FAULT (alarm fault), that return true/false values.
- Non-mathematical functions, such as the CurrentLanguage function that returns the RFC17766 code for the current language of an application.
- If-Then-Else logic that returns numeric or true and false values, depending on how it's structured. These are called conditional expressions because the result of the expression depends on whether the If statement is true or false. When the If statement evaluates to True the result is defined by the Then statement. When the If statement is False the result is defined by the Else statement.

Use expressions in:

- Graphic displays
- Alarm setup
- Information setup
- Macros
- Global connections

## See also

The Expression editor

Quick reference to math functions

Quick reference to operators

Causes of run-time errors for expressions

Examples: Expressions

Keywords: expression