From Dirk W. Hoffmann:
VirtualC64 emulates a Commodore 64 personal computer. I wrote the software with two major goals in mind. First, I wanted to create an emulator that can be used as a demonstrator program in a first year or second year course on computer engineering. To achieve this goal, I have integrated various debugging capabilities that let you peek inside the CPU, RAM, ROM, or one of the custom chips. Second, I tried to make the emulator as user friendly as it can get.