[XM, XN, XO, and XP are optional register parameters, such
that 10 <= M,N,O,P <= 99. On completion of the operation,
XM contains the picture minimum, XN its maximum, XO its
average, and XP its standard deviation. If register are not
provided the values are placed in the following registers:
X3, X4, X5, X6.]
.INPUT FILE: PIC001
[Enter name of file to be analyzed.]
.MASK FILE: MSK003
[Enter name of file containing mask.]