ls says in green what the shell will start

Directories were already blue. Something the shell will run is green now,
and it is asked by LOOKING rather than looked up.

This was priced once as needing a runnable bit in the directory entry,
set by the filesystem from a list of magic numbers it would have to be
taught - declined twice, for putting format knowledge in the filesystem
and giving two implementations a registry to keep in step.

It costs nothing of the sort any more. The shell decides what to run by
reading a file's first block, so "will this run" is a question with an
answer already, and this asks the same one the shell would: SBEX for a
program, "#!" for a script. Nothing is written down and nothing has to
agree about anything.

The price is a block read per file, which is exactly what the bit existed
to avoid: a listing of thirty seven files went from 260,593 cycles to
635,321. It is paid in ls and not in dir on purpose - dir is the listing
you audit and is built into the shell, this is the one you read and was
loaded off the disk anyway. The fast one stays fast.

plain.script is the proof on the test disk: it sits among a dozen scripts
that are green and is not one, because it is the fixture with no shebang
and the shell will not start it. The extension is decoration and the
colour is the truth, which is the whole of what running by content means,
finally visible.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Programs/CosmOS/README.md

@@ -724,6 +724,17 @@ sorting. Nothing here sorts; entries come back in the order the directory holds
 order arbitrary, down-and-across buys nothing and costs a division on a machine that cannot
 divide. If sorting ever arrives, that is the moment to change it.
 
+**Something that will run is green**, and that is asked by looking rather than looked up. The
+shell decides what to run by reading a file's first block, so "will this run" already has an
+answer and this asks the same question the shell would: `SBEX` for a program, `#!` for a
+script. It costs a block read per file, which is exactly the price a *runnable bit* in the
+directory entry was proposed to avoid - and that bit was declined twice for putting format
+knowledge in the filesystem and giving two implementations a registry to keep in step. Paying
+the price here instead buys the same listing and writes nothing down.
+
+It is paid in `ls` and not in `dir` on purpose. Reading every file roughly doubles what a
+listing costs; `dir` stays the fast one, and this one was loaded off the disk anyway.
+
 **The width comes from the screen**, port `0x32`, which is 80 while CosmOS is running because
 CosmOS asks for the wide mode as it starts.