What is the GAC? What problem does it solve?

Purpose:

• Any developer that has written and deployed a non trivial, multi environment system would have come into contact with the GAC, frequently for frustrating reasons.
• A lack of knowledge about the GAC might indicate a lack of experience in writing professionally deployed multi environment code.

Potential Answer:
GAC stands for Global Assembly Cache. It is a machine-wide code repository or cache where the registered assemblies must have a strong name and version number. This is required to the problems of versioning, and what has become known as DLL hell when libraries become out of date with updates etc...