.GMC file extension

This is the basic program to work with .GMC extension

Global Mapper

Global Mapper Global Mapper Catalog File

Global Mapper is an easy-to-use spatial data management tool for GIS mapping. It lets you import and export data from your spatial databases in over 250 different spatial data formats including Esri ArcSDE, MySQL Spatial, Oracle Spatial, PostGIS/PostgreSQL, etc... (more)

The program works with the following extensions: opt, gms, gmc, gmg and gmp

.GMC extension is also supported by the following program:

Collectorz.com Game Collector

Collectorz.com Game Collector Game Collection

This application allows you to add your games to a database on your computer.