Hi!
I could only dig up the GIF 87a documentation, but the 89a is
pretty much the same. The big differences (that I noticed, I mostly
just skimmed them over) included fleshing out the extension blocks
and noting that if an encoder did not choose to send a clear code,
the decoder had to keep decoding without resetting or adding codes
until the clear code was received. I don't believe anyone will
expect this in version 87a.
tgif.c displays GIF images on a two toned display. It is a nice
example of a GIF decoder.

Hang loose!
- Video Cougar