Convert UNIX to DOS format using sed command

Type the following command if you are using bash shell:
$ sed 's/$'"/`echo \\\r`/" input.txt > output.txt

Convert DOS newlines (CR/LF) to Unix format using sed command
If you are using BASH shell type the following command (press Ctrl-V then Ctrl-M to get pattern or special symbol)
$ sed 's/^M$//' input.txt > output.txt