listamsb: tweak a warning, expand DIAGNOSTICS in man page.

1 files changed, 18 insertions, 2 deletions

diff --git a/listamsb.rst b/listamsb.rst
index ad0c897..acf3718 100644
--- a/listamsb.rst
+++ b/listamsb.rst
@@ -69,10 +69,26 @@ BASIC file.
 
 - not an AMSB file: first byte not $00
 
+  Pretty self-explanatory: if the file doesn't begin with a *$00* byte,
+  it's not a tokenized AMSB file.
+
 - not an AMSB file: too big (*N* bytes), won't fit in Atari memory
 
+  The file can't be a tokenized AMSB file because there was no way
+  for it to be created. It must be some other kind of file that begins
+  with a *$00* byte.
+
 - not an AMSB file: program size too small (*N*). Atari BASIC file?
 
+  The program header claims the file is 0, 1, 3, or 4 bytes long. This
+  is impossible, so this isn't an AMSB file. A lot of Atari BASIC
+  programs begin with three *$00* bytes, so that might be what this is.
+
+- program length is 2, no code in file (SAVE after NEW)
+
+  Probably, someone did a SAVE when there was no program in memory. It
+  could also mean this isn't an AMSB file at all.
+
 Warnings
 --------
 
@@ -93,11 +109,11 @@ continues processing.
   The program contains a line number that's greater than *63999*. How
   did that happen?
 
-- line *N* has character *C* outside of a string, maybe not an AMSB file?
+- line *N* has character *C* outside of a string. maybe Atari BASIC?
 
   This happens when ATASCII codes 0 to 31 (*$1f*\) appear in the program.
   AMSB can create files like this, but at runtime, it's a syntax error.
-  It could also mean it's not really an AMSB file.
+  More likely, it means this is an Atari BASIC file.
 
 - actual program size doesn't match program size in header