$($a$)$ Write the pseudocode for a login shell, which prompts the user to input a login name and a password. The shell then invokes a

service function validate$($name$,$ password$),$ which returns $1$ if the name and password are valid, and $-1$ otherwise. If the entry is

valid, the login shell creates a new process for the user. Otherwise, the shell displays an error message and restarts. Also, the shell

contains a back door that allows illegal entry without a password whenever a user enters "superman" as the user name.