Texas Instruments TI-83 - page 241

TI-83 Plus Draw Instructions 238
Using pxl.Test(
pxl.Test( (pixel test) returns 1 if the pixel at (row,column) is turned on or 0 if
the pixel is turned off on the current graph. row must be an integer
between 0 and 62. column must be an integer between 0 and 94.
pxl.Test(row,column)
Split Screen
On a Horiz split screen, the maximum value for row is 30 for Pxl.On(,
Pxl.Off(, Pxl.Change(, and pxl.Test(.
On a G.T split screen, the maximum value for row is 50 and the maximum
value for column is 46 for Pxl.On(, Pxl.Off(, Pxl.Change(, and pxl.Test(.