Create a shell script (tcsh or bash) that is able to backup all *.txt program files in your current directory.

• If a backup directory does not exist, then ask the user input a backup directory name, and make/create the backup directory (in your current working directory)
• If the backup directory was successfully created or already exists
  • For each .txt file:
    • If the file does not exist in the backup directory, then copy the current file to the backup directory and print a message that the file has been backed up.
    • If the file already exists in the backup directory, compare the updated time of the two files; if the backup file is out of date, copy the file and prompt a message, otherwise, do nothing.