how can i write a program to print username and password if the minimum and maximum length of password are 5-15 respectively. please give me answer as soon as possible

First idea, is to use a keyboard and editor, ;) but seriously, read up on permutations and programming in general. This is not a trivial "Hello World" kind of program.

Second idea, is to consider that hacking into someone's computer is a crime in most jurisdictions, and that your time and effort is much better spent, elsewhere.

Now that's enlightenment! ;)