Sticky keys

Sticky keys is an accessibility feature of some graphical user interfaces which assists users who have physical disabilities or help users reduce repetitive strain injury. It serializes keystrokes instead of pressing multiple keys at a time, allowing the user to press and release a modifier key, such as Shift, Ctrl, Alt, or the Windows key, and have it remain active until any other key is pressed. 
Sticky keys functionality is available on/in Microsoft Windows and macOS as Sticky Keys, and on Unix/X10 systems as part of the "AccessX" utility.
History.
Sticky Keys was first introduced to Mac OS in System 6 as part of the "Easy Access" extension, which also included mouse keys functionality.
In 1994, Solaris 2.4 shipped with the "AccessX" utility, which also provided sticky keys and mouse keys functionality.
Microsoft introduced Sticky Keys to the Windows platform in Windows 95.