Use a text editor to inspect a mail file on the computer on which you keep your electronic mail. Assuming it is similar to the Berkeley mail system, you should be able to recognize message boundaries as well as the massage sender, receiver, subject line, and so on. Write an access method to read such a mail file and to print an index with one line per mail message. The line should print the sequence number of the message, the sender, the time and date the message was sent, and the first 20 characters of the subject field.