In Texis version 6, the default Vortex source file extension is
.vs" for clarity. Empty (no extension) is still accepted
for back-compatibility. The source extension need not be specified on
the command line nor URLs. Under Windows, a file mapping is added at
installation to map
.vs to Wordpad or another editor.
The source extension is changeable (not recommended)
in texis.ini via
[Texis] Vortex Source Extensions (here).