GIF File Output in IDL

QUESTION: My colleague seems to be able to produce GIF file output in IDL, but I can't. What am I doing wrong?

ANSWER: Nothing, probably. A compression algorithm used in GIF file output was patented and held for a long time by the Unisys Corporation (via their CompuServe subsidiary). At one point they threatened to enforce their patent with companies that allowed users to create GIF file output. Research Systems was put off by this approach and choose to remove GIF file output from IDL in version 5.4 of IDL. The patent recently expired and now anyone can write GIF file output without fear of prosecution. As of IDL 6.2 it is now possible to write GIF files, as before. You probably can't write GIF files because you are using a version of IDL that doesn't support it.