2013/2/12 John Brown <johnbrown105@hotmail.com>
In a MSYS window, `cat output.dat' prints
 %TOTAL O¸'.23

Notepad displays it as
 ‰TOTAL Œ¸‚.23

2013/2/13 John Brown <johnbrown105@hotmail.com>
If MSYS uses ANSI by default, and Notepad uses ANSI by default,
then why is the file not displayed the same in both windows?

Have you noticed how similar they look like? Try applying the same font for the terminal and the text editor, and it should look equal as you want.