
ZCRD.83P is a "utility routine" for drawing playing cards to the screen.
It takes three parameters: A, B, and C.

A and B are the X and Y pixel coordinates of the card, measured from the
top left corner of the graphics screen.

C is one of the following:

  0..51:  Draw the card with value (C mod 4) and suit (C/4), where
the order of the suits is CDHS, as in bridge, and the order of the
values is ace through 10, J, Q, K. Since both sequences are zero-based,
it's important to realize that if you want to display the 10 of clubs,
you must actually set C equal to 9! In practice this is nice, because
writing "9" instead of "10" saves one byte of program storage.

  -52..-1: Draw the face of the card as if C were -(C+1), but do not
draw the border of the card. This can be used to "turn up" a card
without making the border blink out for a moment, or if the card is
partly hidden under a stack.

  52 or greater: Draw only the border of a card, with no face. This
can be used to display a "face-down" card.

  -53 or less: Undefined.

ZCRD.83P is placed in the public domain by its author.
