User interface expert Jef Raskin coined the term "quasimode" to describe the state a computer enters into when a modifier key is pressed.
This could be considered confusing, since the original space-cadet keyboard and the X Window System recognize a "Meta" modifier distinct from "Super".
The MSX computer keyboard, besides Shift and Control, also included two special modifier keys, Code and Graph.
The MIT space-cadet keyboard had additional Top and Front modifier keys.
Specialist typesetting machines, and word processors such as the Redactron, sometimes used multiple modifier keys to trigger mode changes e.g. for emboldened text or justification changes.
This approach gradually became obsolete after software based on commodity hardware and operating systems adopted the WIMP metaphor which provided drop-down menus etc.
Keyboards of some languages simply include the accented characters on their own keys.
Some keyboards also have a Compose key for typing accented and other special characters.