This will tell you on what machines IDL is running, how to set up your environment, how to set your display, and where the documentation is. A few basic hints that will help you get started with the command line interface. To repeat a command, you can go up and down through previous commands using the arrow keys. IDL can be run by typing commands interactively, by creating programs interactively, by reading programs in from the command line, or it can be run in batch mode. When you type commands on the command line, each line is executed immediately when you hit the return key.
Batch mode Running in batch mode is similar, except the commands come from a file.
This will execute the four commands exactly as if you had typed them. When typing interactively and running in batch mode, each line is executed immediately. You can write programs which can be stored and run multiple times, and you can write functions which may be called from programs and other functions. The examples above make it look like batch mode and running programs is very similar. Consider the following simple computation of the factorial function.