Subchapters:

Introduction

Interactive Data Language

Interactive: Ready to use, command line actions:

IDL> plot,x,y,xrange=[100,500],/ylog

and a plot is born...

IDL is always running in a kind of Debugger mode. Variables are accessible in R and W.

Data: easy to manipulate arrays like vectors, images and 3-4D dataset:

IDL> Image = (Obs - Flat) / (Dark - Flat)

Language: a la Fortran or C:

programs with routines and functions call

if endif else endelse blocks

for loops (but array manipulations are loopless)

pointers

widgets

OO

IDL is compiling on the run the procedures and function it needs.

There is a way, under IDL6.0, to generate programs that can be run without IDL license (IDL Virtual Machine).