Thanks for linking this. Though I've never met Walker, I was introduced to ANIMAL around 1977 on a Univac 1108. That was after the PERVADE subroutine quit working due to the release of a new version of the Exec-8 operating system. I was working then as an 1108 FORTRAN programmer, and learning 1108 assembly. Walker's code was a great example to learn from.

I suspect the earliest versions were written in the '50s when Claude Shannon and David Huffman were working on compression algorithms.

P.S. The reason ANIMAL and PERVADE are in all caps is that the 1108 used a character set called FIELDATA http://bit.ly/10w9dwq wherein a 36 bit byte, or word comprised six 6 bit characters...no lower case. We thought in octal, not hexadecimal.

When they made ASCII available, there were 4 9-bit bytes to the word