data structure used to implement UNDO and REDO option

I want to implement UNDO and REDO option(as we see in MS word etc). Can you suggest me a data structure for it, and how can i implement it.?

It isn't a data structure but a design pattern. You're looking for the Command Pattern.

The standard is to keep the Command objects in a stack to support multi level undo. In order to support redo, a second stack keeps all the commands you've Undone. So when you pop the undo stack to undo a command, you push the same command you popped into the redo stack. You do the same thing in reverse when you redo a command. You pop the redo stack and push the popped command back into the undo stack.

Actually, the standard pattern for this functionality (Gang of Four, even) is Memento.

Also, while most programs use Undo/Redo stacks, afficionados of certain text editors prefer Undo/Redo trees so that they don't lose their entire history if they undo a few commands, try a new one, and change their minds.

Objective-C Cocoa has a well documented anwser named NSUndoManager.