A number of things happen before you see the login: prompt on your terminal. After you enter the login name, the login program is started. It finishes the process of logging you in by prompting for a password, checking the /etc/passwd file, and finally starting up your login shell. Your login shell is specified in the /etc/passwd file like this:
For larissa, the login shell is /bin/sh, while for renata it is /bin/ksh.
To make the Korn shell your default login shell, have your system administrator change it to /bin/ksh or the pathname of wherever the Korn shell binary is located, or run the chsh command (if available on your ...