I had some file formats I had to import into a database for work and it was in a strange format I had never seen before.
I saw the word EBCDIC, and I was clued in that I was not using ASCII. I read somewhere that Mac still uses EBCDIC.
http://www.natural-innovations.com/computing/asciiebcdic.html is Google's top link for EBCDIC. But here is a cleaner looking table comparing ascii and ebcdic: http://www.simotime.com/asc2ebc1.htm
Wikipedia's link: http://en.wikipedia.org/wiki/EBCDIC
But what finally helped was when I found: http://www.discinterchange.com/reading_COBOL_layouts_.html
and then used http://www.discinterchange.com/TechTalk_signed_fields_.html to figure out signed fields like above.