If you are using ENVI, you can extend and customize it with IDL. You must have the ENVI software installed and licensed.
To start ENVI 5.0 from the IDL command line, type:
e = envi()
To start ENVI Classic:
From the Start menu: Select All Programs > ENVI 5.0 > Tools > ENVI Classic or ENVI Classic + IDL
From the IDL command line: Type envi
For more information on features available in ENVI, see the ENVI online help.
See also Extending ENVI with IDL.