newbie: use <CR> in RE?

[Zhang Weiwu]

Hello. Just want to know how to use special character in Regular Expression.

I wish to remove all the carrier returns from a text file, I can use:
tr -d "\r" < text_file > modified_text_file
But if I do:
sed -i s/\r//g text_file
it actually removes all the character "r" from the file.

This is also a problem in vi(1). Besides <CR> I wish to manipulate 
tabstops and line-feeds with RE too.