Format fix 1980s and 1990s README.md files

I also updated the todo.md file as I left some things out that have to
be done. I only explicitly named one thing but when I go over them as a
final pass I will address the things in question (some will require
discussion).

1989/README.md

@@ -1,14 +1,12 @@
-1989 marked the "The Sixth International Obfuscated C Code Contest"
+# 1989 marked the "The Sixth International Obfuscated C Code Contest"
 
-
-Look at the README.md file for the given winner for information
-on how to compile the winner and how to run the winning program.
+Look at the README.md file for the given winning entry for information
+on how to compile it and how to run the winning program.
 Look at the winning source and try to figure how it does what it does!
 You may then wish to look at the Author's remarks for even more details.
 
-Instructions for use: Run make to compile entries (it is possible
-that on System V or non-unix systems the Makefile needs to be
-changed).
+Instructions for use: Run `make` to compile entries (it is possible that on
+System V or non-Unix systems the Makefile needs to be changed).
 
 This year, the Grand Prize was given to the most useful program.
 
@@ -17,16 +15,17 @@ to stress the fact that starting in 1990, compiling entries must result an
 executable regular file.
 
 The Makefile always uses the portable version of the ["Best
-self modifying program"](fubar/) because there is no loss of functionality in
-using it.  In the case of the ["Best game"](tromp/) winner, however, some
+self modifying program"](fubar/README.md) because there is no loss of functionality in
+using it.  In the case of the ["Best game"](tromp/README) winner, however, some
 functionality is lost in the portable version and so the Makefile uses
-the original program.  System V users may need to change the Makefile
-to use the s5 version.  See the hint files or the Makefile for details.
+the original program. System V users may need to change the Makefile
+to use the s5 version. See the hint files or the Makefile for details.
 
 [Rules](rules.txt) and results were posted to comp.lang.c, comp.sources.unix, and
-alt.sources.  They have been made available on a wide number of Usenet
+alt.sources.  They have been made available on a wide number of USENET
 archive sites such as uunet.  The 1989 winners will be published in the
-Micro/Systems Journal.
+[Micro/Systems
+Journal](https://www.vintage-computer.com/publications.php?microsystemsjournal).
 
 =-=