The following is a list of all routines included in IDL, categorized by functionality:

3D Visualization

Animation

Array Creation

Array Manipulation

Asynchronous Job Classes

Color Table Manipulation

Date and Time

Debugging

Dialog Routines

Direct Graphics

Error Handling Routines

ESE Classes

Executive Commands

External Linking

Font Manipulation

Graphics

Help Routines

HTTP and Web-Related Routines

IDL Tasks

Image Processing Routines

Input/Output

iTools

Language Catalogs

IDL Machine Learning

Mapping

Mathematics

Object Class Library

Operating System Access

Programming and IDL Control

Query Routines

Saving/Restoring a Session

Scope Functions

Signal Processing

Statements

String Processing Routines

Structures

Type Conversion

Variable Functions and Attributes

Widget Routines

Widget Routines, Compound

Window Routines