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Unofficial Name: IVertLine

BCALL Address: 55BAh

Draw a vertical line.


  • DE = X coordinate of line
  • B = Y coordinate of bottom end of line (from bottom of screen)
  • C = Y coordinate of top end of line; must be greater than or equal to B
  • A = 1 to use the current foreground color, or 4 to copy pixels from the graph buffer
  • (penFGColor) = RGB color to draw (if A = 1)
  • (penFGColorIndex) = Color index to store in graph buffer (if A = 1)
  • fullScrnDraw, (iy + apiFlg4) = 1 to use LCD coordinates; 0 to use graph coordinates
  • plotLoc, (iy + plotFlags) = 1 to draw to LCD only; 0 to draw to LCD and graph buffer




  • Interrupts disabled


This routine is analogous to calling IPoint several times for a vertical row of pixels, but somewhat faster. Like IPoint, A may either be 1 (to draw with the current foreground color), or 4 (to copy pixels from the graph buffer to the LCD.) The other IPoint operations are not supported.

Unlike IPoint, this routine does not check that the input coordinates are valid (i.e., within the bounds of the LCD or graph buffer); passing invalid coordinates may have strange effects.