Shell Programming and Scripting

Hi,
I have file generated in HP-UNIX environment (for Example) with the line feed (i.e $):
a$
b$
C$

Now, I need to append CTRL-M character at the end of each line, but the last line of the file should not have both CTRL-M and Line Feed (i.e ^M and $). The file should look like:
a^M$
b^M$
c

Please help me how to achieve this using the shell script
Thanks in advance
Mohan.N

Look closer tools like unix2dos & dos2unix it removes this kind of signs.

Or if you prefer to add it manually,
vi <filename>
go to end of each line <press $>
add ^M character <press CTRL+V followed by CTRL+M>