About the algorithm:
The elements are horizontal, vertical, 45 degree lines, square waves, zig-zags, and probabilities for line widths and lengths. For each position in a matrix (left to right, top to bottom), the algorithm randomly chooses a new element from the alphebet to add to the exisiting elements.
In P-26, when the middle postion is reached, an element is subtracted from the composite sign in the order in which it was added. Thus the last position in the grid shows the last element added.
In P-28, elements are continually added until the last grid position.

First published:
Catalog, Manfred Mohr, "Computer Graphics, Une esthétique programée", ARC - Musée d'Art Moderne, Paris, 1971