Hello again,
I tried to find it in this book but I failed. But later found it in doc 
Kernel#printf is similar to C printf. This is not homework, but part of 
my script (I prepare histogram and learn Perl-like system scripting), 
however, you are right I should have googled it more widely.

Thanks for patience and sorry,

-- 
Posted via http://www.ruby-forum.com/.