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
• 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