unprotbas: code readability (constants), mention rev B BASIC in doc.

1 files changed, 13 insertions, 5 deletions

diff --git a/unprotbas.rst b/unprotbas.rst
index 1df865f..4228d91 100644
--- a/unprotbas.rst
+++ b/unprotbas.rst
@@ -208,11 +208,19 @@ Bad next-line pointer
 
 One more thing **unprotbas** can do is remove extra data from the end
 of the file. It's possible for BASIC files to contain extra data that
-occurs after the end of the program. Some programs use this as a way
-to load arbitrary binary data into memory along with the program; for
-other programs, the extra data is truly garbage (e.g. an EOF character
-if the file came from a CP/M system, or padding to a block size if a
-dumb implementation of XMODEM was used to transfer the file).
+occurs after the end of the program. Such data might be:
+
+- Arbitrary binary data used by the program at runtime, such as
+  machine language routines, or fonts.
+
+- Zero bytes, caused by SAVEing the program with revision B BASIC. Every
+  time a program is LOADed, edited (or not) and then SAVEd again, 16
+  bytes of extra (garbage) data gets added to the program. To avoid
+  this, don't use revision B (use rev C if possible, A otherwise).
+
+- Garbage added by some system previously used to store or transmit
+  the file. CP/M systems might add an EOF (^Z) character. Dumb
+  file transfer software might pad the file up to its block size.
 
 Normally, such "garbage" doesn't hurt anything. BASIC ignores it. Or
 it normally does... if you suspect it's causing a problem, you can