About Program and Data SAVE Files

The SAVE procedure can be used to quickly save IDL routines and data variables in a binary format that can be shared with other IDL users, or with others who have installed the IDL Virtual Machine. If you are developing an application for distribution to users who do not have a version of IDL installed, you should also see Distributing Runtime Mode Applications.

Warning
Variables and routines cannot be stored in the same SAVE file.

Note
While IDL routines or data can be saved in a file with any extension, it is common to use the extension .sav for SAVE files. Using the .sav extension has two benefits: it makes it clear to another IDL user that the file contains IDL routines or data, and it allows IDL automatically locate and compile the routines in the file as described in Automatic Compilation.

If your program or utility consists of multiple routines, each procedure or function used by your program must be resolved and contained in a SAVE file. You have the following options:

Include all routines in a main SAVE file that is restored first. This makes all routines available without having to restore any additional SAVE files. You can do this manually, by compiling all of the routines yourself (possibly with the assistance of the RESOLVE_ALL or IRESOLVE routines).

Create a separate SAVE file for each routine used by your application. Assuming each SAVE file uses the .sav extension and has the same name as the procedure or function it contains, this allows you to simply place the files in a directory included in !PATH; IDL will compile all of the files automatically when needed.

If your program also contains variable data, you must create a separate SAVE file to contain the data. Variable data must be explicitly restored before any routine attempts to use the variables contained in the file. See Executing SAVE Files for more information.

Note
A SAVE file containing data will always be restorable. However, SAVE files created prior to IDL version 5.5 that contain IDL procedures, functions, and programs are not always portable between different versions of IDL. If you created your SAVE file with a version of IDL earlier than 5.5, you will need to recompile your original .pro files and re-create the SAVE file using the current version of IDL.