Thanx a lot guys for all of yours feedback, I have also checked one of the previous discussions on "" and as you've said it is the Proakis' and Oppenheim's books.
"digital signal processing" authored by "oppenhiem" covers almost every aspect of the issue both theoretical and practical. and it aslo has lots of examples and practice problems.
John_OR, I haven't found this book to download so I bought it some years ago. There is a book here at EDA that has kind of the same content, is very similar, but the difference is that the Orfanidis book has a lot of code examples in C and Matlab.