The Start menu was introduced in Windows 95 and Windows NT 4.0, but had been worked on at Microsoft since 1992, originally being labelled as "System" to testers of the time. It was made to overcome the shortcomings of Program Manager in previous operating systems. Program Manager consisted of a simple multiple document interface (MDI) which allowed users to open separate "program groups" and then execute the shortcuts to programs contained within. It lacked the ability to nest groups within other groups.