OSBYTE &71

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OSBYTE &71 (113) - Select Main/Shadow for Display hardware

   On entry:
       X=0 Use whatever memory the current screen MODE uses
       X=1 Use main memory
       X=2 Use shadow memory
   On exit:
       X=preserved
   RISC OS:
   The value of X can be greater than 2 as well, and instructs the video
   hardware to use the bank at screenbase+(X*modesize)

This call specifies which bank of memory the Master video display hardware accesses. Using this and OSBYTE &70 a program can use the VDU to write to one bank of memory while the other is being displayed.

The setting is stored in the OSBYTE &FB variable.

See also

Jgharston (talk) 01:12, 4 April 2015 (UTC)