Twenty four more sites, and the interesting part is which ones were left
alone. A rule emerged while reading them and it held all the way through:
apply where the repetition is INSIDE one operation, skip where the author's
own structure says it is a new thought, and never where two equal values
mean different things.
Taken:
- Five registers reassigned to a value they already held, where both are
the same quantity: two masks in one expression in Snake, two spaces
printed by the monitor, both halves of block zero in waitTest, and a RSTA
in Pour that the very next instruction overwrote.
- Eighteen SETDs that reload a pointer inside one operation - a store back
into the variable just read, or an INCD stepping to the second byte of a
two byte value. Those read correctly without the reload.
- sbfsNext, which branched to the label on the line below it.
Left, with reasons that are the useful part of this:
- Eight registers where the same number means two different things. CosmOS
and the loader set A to 1 for a blit command and then to 1 again for a
bank number; Asm compares a type against 3 and then a status against 3.
Removing those couples one quantity to another that is equal by accident
and would part company silently.
- Ten RSTAs that open the RSTA/RSTB/CCF/ADD "return zero" block. The
redundancy is what makes that idiom self contained; taking it out makes
the return value depend on the line above.
- Eleven SETDs that begin an arm of a comparison chain. Each arm loads,
compares and branches, and they get reordered - the repetition is the
reason a new arm can be dropped in anywhere.
- Twenty five SETDs separated from their pointer by a blank line or a
comment, which is the author saying a new thought starts here.
- Two CCFs before arithmetic, which this codebase writes unconditionally.
- Three redundant branches in test programs whose recorded output includes
addresses, where three fewer bytes moves what the test demonstrates.
Nine recorded outputs moved and every one is a size in a listing or, for
Life, five more generations inside the same cycle budget. Behaviour is
unchanged everywhere: cosmosSnake and cosmosEdit pass byte for byte while
Snake loses eight bytes and Edit twelve.
CosmOS is 10,902 bytes of program against 10,937, and the native assembler
12,173 against 12,183. The CosmOS README's size for Edit moved twice in one
sitting, and this morning's check caught it both times - which it could not
have done before that claim was reworded to name what it was about.
The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and
applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit,
which is fifty one bytes short of the line, and the next thing added to it
went over.
GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an
application says where it goes with #Base and the loader puts it there, so a
CosmOS that has grown past 0x1FFF simply has the next program loaded written
over the end of it. What breaks is whichever part of the shell that program
happened to cover, at whatever later moment somebody uses it. It turned up here
as the monitor's assemble command answering "I do not know" to valid
instructions, several commands into a session, on a machine that had booted
perfectly well.
Both halves are doubled: applications now start at 0x4000 in Program Memory and
0x2000 in Data Memory. That is 16K of code and 8K of data for the system,
against the 8775 and 2948 it uses today. Both were on the same trajectory, and
moving them together means the twenty files that say #Base are edited once
rather than twice.
The standalone loader's loadable.asm keeps its old base: it belongs to the
loader CosmOS grew out of, not to CosmOS, and its addresses answer to a
different program. The unbased-segment diagnostic keeps its old base too - it
exists to produce an error message that names the address, and the message is
what is recorded.
Tests/docs.sh now reads the two limits out of the table in the README and
measures both segments against them. It reads them rather than being told them
because the table is the specification, and this is the second time in this
project that the thing nobody checked is the thing that rotted.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
Anachronaut
