Help on Package_Name

[19owls <19@owls.org>]

Hi. It's my first day with Ada. heard many wonderful things about it.
i'm not studying programming, but i've done basic C before.
obviously i've read and managed to compile the infamous
Hello World!

i have a beginners book on Ada, it keeps referring to student_io package
name for the exercises and examples which is not known to gnat. i need to
know what package name to use whilst handling text, calculations,strings
and so on beyond text_io (which handles strings only i suppose).

in future how do i know of the list of package names to use and what it is
for? thanks.