How to add a custom field in the WordPress editor, and get its value?

I want to add a custom input under the title in WordPress editor, for pages only. (as long as it shows in pages, it’s okay, it can show in other places too). Then I want to get post that value in the page if it’s not equal to nothing.

I just need to know how to put the value and how to get that value in the page. It’s pretty much the same with custom fields, and then called by meta data, but instead of adding a custom field, I want an input box to appear.

Thanks.