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Many of the options in the main menu relate to setting up standard bitplanes. Aside from setting or clearing them individually or collectively, they can be seeded with random points according to four densities. These are high, medium, low, and sparse; in each case the actual number is a variable which can be set by the parameter options.

Probabilities are all given in mils; n per thousand, making 500 correspond to 50% probability, or equal likelihood. Sparse refers to a fixed number altogether, whose locations are chosen at random.

Often it is desired that only a small portion of a plane be occupied, allowing the expansive properties of a rule to be judged. To produce this contrast, the random points can be confined to the interior of a slightly skew ellipse, whose radius and density are also parameters.

Checkerboards with squares of different sizes represent another useful variant on standard initial configurations; provision also exists for setting them up.

The design of the CAM hardware allows the possibility of writing to multiple planes, but confines reading to a single plane. Following the hardware rigorously results in operations on the plane having a hexadecimal parameter ranging between 0 and f while writing, but a decimal parameter lying between 0 and 3 for reading. The hexadecimal parameters are microprogrammed in the obvious way.

It is possible to adjust the planes and to permute them, but so far these options have not been worked out with the full care which they deserve, and are still likely to vary from one version to another.

Harold V. McIntosh