The munching squares hack consists of drawing Y = X XOR T for a range of X and T over and over until all the possible combinations of X and T have come up. It was reportedly discovered by Jackson Wright in 1962 and took 5 instructions of PDP-6 code.

-window

Draw on a newly-created window. This is the default.

-root

Draw on the root window.

-mono

If on a color display, pretend we're on a monochrome display.

-install

Install a private colormap for the window.

-visual visual

Specify which visual to use. Legal values are the name of a visual class, or the id number (decimal or hex) of a specific visual.

-delay microseconds

How long to wait before starting over. Default 5000.

-xor

Use the XOR drawing function. (Default.)

-no-xor

Don't use the XOR drawing function.

-shift

Start drawing the square at weird starting points. (Default.)

-no-shift

Don't shift and start drawing the square at weird starting points.

-logminwidth minimum-width

The logarithm (base 2) of the minimum with of a square (must be a power of 2, or some parts of the square aren't.)

DISPLAY

to get the default host and display number.

XENVIRONMENT

to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

ITEM 146: MUNCHING SQUARES

Another simple display program. It is thought that this was discovered by Jackson Wright on the RLE PDP-1 circa 1962.

    DATAI 2
    ADDB 1,2
    ROTC 2,-22
    XOR 1,2
    JRST .-4

2=X, 3=Y. Try things like 1001002 in data switches. This also does interesting things with operations other than XOR, and rotations other than -22. (Try IOR; AND; TSC; FADR; FDV(!); ROT -14, -9, -20, ...)

ITEM 147 (Schroeppel):

Munching squares is just views of the graph Y = X XOR T for consecutive values of T = time.

ITEM 148 (Cohen, Beeler):

A modification to munching squares which reveals them in frozen states through opening and closing curtains: insert FADR 2,1 before the XOR. Try data switches =

    4000,,4    1000,,2002    2000,,4    0,,1002

(Notation: <left half>,,<right half>)

Also try the FADR after the XOR, switches = 1001,,1.