Can i create a unix system in windows?

i've used putty to do c programming in college, but i was always connected to their server to program, but the thing is, i have been disabled because im no longer in the course, im quite a noob still about all this stuff but is there a way i can make a unix system file or folder or anything like that so i can connect to it using putty and program my self? or is there a server out there that is free that i can connect to?