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Hypothesized Official Name: ClearRect

BCALL Address: 4D44h

Fill a rectangle with solid white.


  • HL = X coordinate of left edge
  • DE = X coordinate of right edge (must be at most 319)
  • B = Y coordinate of top edge (from top of screen)
  • C = Y coordinate of bottom edge (must be greater than or equal to B and at most 239)



  • AF


The rectangle is drawn only to the LCD, never to the graph buffer.

The dimensions of the filled area are (HL-DE+1) × (C-B+1). The routine checks for HL > DE (in which case nothing is drawn), but doesn't check for B > C, and doesn't check that the provided coordinates are valid.

The interrupt state (IFF) is preserved.