munch man page

munch — munching squares


munch [-display host:display.screen] [-foreground color] [-background color] [-window] [-root] [-mono] [-install] [-visual visual] [-delay usecs] [-xor] [-noxor] [-clear number] [-simul number] [-classic | -mismunch | -random] [-fps]


The munch program performs the munching squares hack. It picks square size, position, and gravity randomly. It also displays a creatively broken misimplementation of the classic algorithm.

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.


munch accepts the following options:

Draw on a newly-created window. This is the default.
Draw on the root window.
If on a color display, pretend we're on a monochrome display.
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 usecs
The delay between steps of the animation, in microseconds. Default: 2500.
Use the XOR drawing function. This is the default.
Don't use the XOR drawing function.
-clear number
Number of squares to misdraw before clearing the display. Default: 65.
-simul number
Number of squares to misdraw simultaneously. Default: 5.
Draw classic munching squares only.
Draw "mismunch" only.
Do one or the other.
Display the current frame rate and CPU load.


to get the default host and display number.
to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

See Also

X(1), xscreensaver(1),



HAKMEM: MIT AI Memo 239, Feb. 29, 1972.

Beeler, M., Gosper, R.W., and Schroeppel, R.

"Unless otherwise stated, all computer programs are in PDP-6/10 assembly language."


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

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.


Explore man page connections for munch(6).