Structure of Mac OS "Classic"
"Classic" means any version of Mac OS prior to X - i.e. Mac OS 1.0 through 9.1.
Neither ITS nor Apple support Mac OS Classic any more, so you don't have to answer technical questions about it if you don't feel comfortable doing so.
- "Cooperative" multitasking
Most operations done through the Toolbox
OS itself basically consists of the Finder
"Extensions" loaded during bootup