DOS Operating Systems

Okay. I went to accessories on the PC I'm working on to click on "Calculator". I clicked on "Command Prompt" by accident. I think I pulled up DOS. Can I still use DOS? Are there 65 year olds out there still running their whole office workstations on DOS in the color of Amber? Or, if I type C:\run facebook will my PC explode? Thankfully, I use a MAC, but it brings about all the nostalgia of C:\ command prompts. ~8/12/09