Difference between Synchronous and Asynchronous Postback?

Question

I am getting confused between trap and interrupt. As trap is software driven and interrupt is hardware originated. Every instruction of a program get executed in CPU then how trap and interrupt differs ? A detailed example can help out me. Thanks in advance.

Answer 1

• Asynchronous postback renders only the required part of the page; whereas,
  synchronous postback renders the entire page for any postback.

• Asynchronous postback executes only one postback at a time, that is, if you have two buttons doing asynchronous postback, the actions will be performed one by one; whereas,
  synchronous postback executes all the actions at once.

• Asynchronous postback only modifies the update panel that raises the postback; whereas, synchronous postback modifies the entire page.