# AviSynth Syntax - Internal functions

In addition to internal filters AviSynth has a fairly large number of other (non-clip) internal functions. The input or/and output of these functions are not clips, but some other variables which can be used in a script. They are roughly classified as follows:

- Boolean functions

They return true or false, if the condition that they test holds or not, respectively.

- Control functions

They facilitate flow of control (loading of scripts, arguments checks, global settings adjustment, etc.).

- Conversion functions

They convert between different types.

- Numeric functions

They provide common mathematical operations on numeric variables.

- Runtime functions

These are internal functions which are evaluated at every frame. They can be used inside the scripts passed to runtime filters (ConditionalFilter, ScriptClip, FrameEvaluate) to return information for a frame.

- Script functions

They provide AviSynth script information.

- String functions

They provide common operations on string variables.

- Version functions

They provide AviSynth version information.

$Date: 2011/01/16 12:24:09 $