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OSBYTE &CA (202) - Read/Write Keyboard Status

This byte determines the current state of the keyboard modifier keys
  b0 = BBC/Elk/Master: res   Compact: b0-b2 = EXTEND status             RISC OS: Alt pressed
  b1 = BBC/Elk/Master: res              1=EXTEND, 2=Shift-EXTEND        RISC OS: Scroll Lock set
  b2 = BBC/Elk/Master: res              3=Ctrl-EXTEND, 4=Sh-Ct-EXTEND   RISC OS: Num Lock set
  b3 = Shift pressed
  b4 = Caps lock off
  b5 = Shift lock off
      (ie, b5-4=01: Shift Lock on, 10: Caps Lock on, 11: No lock)
  b6 = BBC/Master/RISC OS: Control pressed             Electron: FN pressed
  b7 = Shift enable (Shift Caps or Shift Inverse)
With Caps Lock on and Shift Enable off, Shift has no effect on letter keys.


  • *FX 202,16 turns Shift Lock on
  • *FX 202,32 turns Caps Lock on
  • *FX 202,48 turns Caps Lock/Shift Lock off
  • *FX 202,160 turns Shift Caps on

Jgharston 22:48, 26 May 2009 (UTC) Jgharston (talk) 20:18, 13 June 2016 (UTC)