Add a few more notes to README.

1 files changed, 11 insertions, 7 deletions

diff --git a/README.txt b/README.txt
index 7a7f46c..47ca0c1 100644
--- a/README.txt
+++ b/README.txt
@@ -102,7 +102,10 @@ Atari or a modern machine.
 
 First, you will be prompted for an input filename[*]. This must be
 a file created by the Save option in dla.xex. The file is read into
-memory immediately.
+memory immediately. Some sanity checking is done: if the file is the
+wrong size (not 3740 bytes), and/or if it has any pixels set in the
+left 3 columns (where dla.xex never puts particles), you'll be given
+the chance to back out (most likely, you typed the wrong filename).
 
 Next, choose the line-ending type. Choices are Atari, Unix (including
 Linux and Mac), and MS (aka MS-DOS or Windows). Choose the system
@@ -112,12 +115,13 @@ Next, you're asked for the output filename[*]. This file will be
 overwritten if it exists (unless of course it can't be overwritten due
 to permissions or the Atari locked-file bit).
 
-Next, the conversion process starts. This takes about half a minute on
-the Atari (for a file with 1000 particles), and is instantaneous on a
-modern machine. Progress is shown as a percentage. When it's finished,
-the output CSV file has been written. On the Atari, you can press
-Ctrl-C during the conversion to abort the process (and delete the
-partial CSV file).
+Next, the conversion process starts. This takes about half a minute
+on the Atari (for a file with 1000 particles), and is instantaneous
+on a modern machine. Progress is shown as a percentage. When it's
+finished, the output CSV file has been written. On the Atari, you can
+press Ctrl-C during the conversion to abort the process (and delete
+the partial CSV file). In case of error (bad filename, disk full, bad
+sector, etc), you'll be given the chance to retry the conversion.
 
 At the end of conversion, you'll be shown the number of particles.
 This includes the seed particles, so e.g. if you used the single-dot