how to set all the character has the same width to display?

[Glen Jackson]

Deal all

I got a problem while configuring gnus. It's about the display format.

Suppose there is a file "test.txt" which contains the following 4 lines:
aaaa
AAAA
0000
OOOO

Command                 The width of each line(display)
emacs -nw test.txt =>   the same width
emacs test.txt     =>   the 2nd and 4th line,is wider

how can I get the same width when i emacs test.txt?

Thanks.