Clarify case-sensitivity in 1990/dds

There was a note that I added that it is case sensitive but it did not
state that it's all caps which is required (the author noted this but
that's further down in the file). This might be one of the only times
caps lock is useful (though still not useful enough to enable :-) )

1990/dds/README.md

@@ -27,7 +27,9 @@ OLD LANDER.BAS
 RUN
 ```
 
-NOTE: this is case sensitive.
+NOTE: this entry is probably one of the only times CAPS LOCK might be worth
+having (though still not useful enough to enable :-) ) as all input has to be
+UPPER CASE.
 
 ## Judges' remarks: