Update some of the 2000 README.md files

I am aware of some entries that do not compile that I haven't even
thought about fixing yet.

I also need to use my linux box to test the X11 entries (this goes for
other years as well) but that'll come at another time as I rarely am at
sitting at that computer. But the README.md files should be in a better
state.

2000/anderson/README.md

@@ -12,10 +12,13 @@ Indonesia
 make
 ```
 
+NOTE: this entry uses `gets()` so you will likely get a warning when compiling
+and/or executing this program.
+
 ### To run:
 
 ```sh
-echo something | ./prog
+echo something | ./anderson
 ```
 
 ### Try: