Example :looking for the name 'John Smith' in the phone book
● Open up the phone book approximately half way
● Look at the name at the top of the page.
● Does Smith come before or after this in the phonebook?
● After, right? So you can ignore the entire first half of the phone book.
● Now open the remaining half about half way.
● You're probably somewhere near the 'T's.
● Does Smith come before or after 'T' in the phonebook?
● Before. So you can ignore the latter half.
● Continue doing this until you find the name for which you're looking.