Contraction of GENealogical inDEX which describes a specification for data exchange.
GENDEX is a specification for the exchange of genealogical data devised by Gene Stark, Professor in the Computer Science Department at the State University of New York at Stony Brook in the 1990s.
Each line in a GENDEX file lists data on a single individual in the following form:
Reference|SURNAME|given name /SURNAME/|date of birth|place of birth|date of death|place of death|
The commercial site operated by Professor Stark based on GENDEX is now defunct. The number of other providers supporting the standard is small (and shrinking).