Alpha Memory

Each display window may or may not have an associated alpha memory depending on the options in the CREATE/DISPLAY command.
The alpha memory is attached to the bottom of the display window and consists of 3 lines, the number of characters per line depends on the width of the image display.
Commands associated with the alpha memory are:
 
LABEL/DISPLAY - write a string into the alpha memory
CLEAR/ALPHA - clear the alpha memory