A core package in a lot of the geospatial applications is a old piece of mathematical code originally written in Fortran (probably in the sixties).   Someone probably in the 80’s recoded the thing pretty much line for line (maintaining the horrendous F66 variable names etc…) into C.     It’s probably ripe for a jump to something else now.

We’ve been through four major generations of the software.    The original was all VAX based with specialized hardware (don’t know what it was written in).    We followed that on with a portable UNIX (but mostly Suns, but ours worked on SGI, Ardent, Stellar, various IBM AIX platofrms, Apollo DN1000’s, HP, DEC Alphas).   This was primarily a C application.    Then right about the year 2000, we jumped to C++ on Windows.    Subsequently it got back ported to Linux.     Yes there are some modules that have been unchanged for decades, but the system on the whole has been maintained.

The bigger issue than software getting obsoleted is that the platform needed to run it goes away.