CompuServe's 1995 announcement that Unisys owned the patent for the LZW compression routine used in GIF files sparked a controversy that continues today. A fine summary of the issues is provided in the article "The GIF Controversy: A Software Developer's Perspective" by Michael C. Battilana, available online at www.cloanto.com/users/mcb/19950127giflzw.html. You can read official information about LZW licensing at www.unisys.com/unisys/lzw. A good set of FAQs about the issue can be found at www-dse.doc.ic.ac.uk/
~nd/surprise_95/journal/vol2/hml/article2.imag4.html.

To find out about recent developments in the GIF controversy, read the article detailing the 1999 GIF "scare" at the LinuxWorld site (www.linuxworld.com/
linuxworld/lw-1999-09/lw-09-vcontrol_3.html). It also presents information about the PNG file format, which was designed to replace GIF as a nonproprietary file format. For more about the PNG standard, refer to Greg Roelofs' book, PNG: The Definitive Guide (O'Reilly and Associates, 1999). You can also enter "GIF," "LZW," or "PNG" in any Web search engine to locate additional articles and information.