HP 38g Graphing Calculator - Manual (Page 166)

PIXOFF Turns off the pixel at the specified coordinates (x,y).
PIXOFF x ;y
PIXON Turns on the pixel at the specified coordinates (x,y).
PIXON x;y
TUNE Toggles the pixels along the line from (xl, yl) to (x2, yZ). Any
pixel that was turned off, will be turned on; any pbcel that was
turned on, will be turned off. TUNE can be used to erase a line.
TLINE x l; y l;x 2 ; y 2
Example TLINE 0 ; 0 ; 3 ; 3
Erases previously drawn 45 degree line from (0,0) to (3,3).
8-14 Programming