This commands pops up a message displaying whatever you put in it. User will have to click "OK" to proceed.
This commands is used to confirm a user about certain action, and decide between two choices depending on what the user chooses. User will have to click on "OK" or "Cancel" to proceed.
This command is used to allow a user to enter something and do something with that information. User will have to click on "OK" or "Cancel" to proceed after entering an input value.