Modern operating systems adhere to a pretty rigid formula. They all have users with password-protected accounts and secure files. They all have restrictions to keep programs from breaking stuff. That design has been common for a long time, but that doesn't make it the best solution. In the late 60s ITS, the Incompatible Timesharing System, was developed as a more exciting alternative. ITS was built for hackers to play, there were no passwords, any anyone who could find ITS was welcome to log in.