Write a robot

This will open notepad.
Write text "This is some text." into it.
Now it close notepad and the popup "Do you want to save" came out.
We send to keyboard letter "n" to be pressed:

Run("notepad.exe")
WinWaitActive("Untitled - Notepad")
Send("This is some text.")
WinClose("Untitled - Notepad")
WinWaitActive("Notepad", "Save"); Under Windows 7
;WinWaitActive("Notepad", "Do you want to save") ; under Windows XP
Send("!n")

Source:
https://www.autoitscript.com/autoit3/docs/tutorials/notepad/notepad.htm

Here is example how to compile AutoIt (au3) application