Changes

The ROM address range is divided by 5 page bits (page 0-31) with 64 10-bit words each, addressed by the 11-bit [https://en.wikipedia.org/wiki/Program_counter program counter].

A stack of four registers (ST1-ST4) is used to call subroutines by the CAL instructions and to return by RTN <ref>[https://cdn.datasheetspdf.com/pdf-down/H/D/4/HD44801_Hitachi.pdf Hitachi HD44801] (pdf)</ref>.

=Chess Programs=