Gail,

i expected this question from you. Since i studied these concepts just to pass the exams, beacuse that time i don't know the real time usage and it will be used in our programming skill, I forgot the concepts.

Once i got the job, then only i realized that all i studied will be applied in the work...anyway hereafter i never forgot this chapters.:)..Thanks for teaching me....Thank you Gail 🙂