[pdp7-unix] Running cas
lars at nocrew.org
Mon Oct 21 17:37:14 AEST 2019
Another interesting piece of information from cas.
The last line in the output for each character looks like label=x-b+number.
Number is an 18-bit value where the top two bits are always "01", then
six bits for the number of 6-bit bytes, and finally 10 zero bits. The
last bits are presumably an offset which comes from x-b.
My guess would be that the WCGA instruction passes an address to the
character generator. At this address is a table of words formatted
according to the previous paragraph. And somewhere near this is the
actual character shape words.
I have noted that the WCGA address is octal 6000, and the kernel ends
right below this. I haven't seen anything that fits the description of
the character generator table. E.g. searching for "amper" doesn't turn
up anything useful.
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