C and
Lisp. Nearly every hacker knows one of these, and
most good ones are fluent in both. Smalltalk and Prolog are
also popular in small but influential communities.
There is also a rapidly dwindling category of older hackers
with Fortran, or even assembler, as their language of choice.
Assembler is generally no longer considered interesting or
appropriate for anything but
HLL implementation,
glue, and
a few time-critical and hardware-specific uses in systems
programs. Fortran occupies a shrinking niche in scientific
programming.
Most hackers tend to frown on languages like
Pascal and
Ada, which don't give them the near-total freedom considered
and to regard everything even remotely connected with
COBOL