An application sends an EM_GETMODIFY message to determine whether the content of an edit control has been modified.
EM_GETMODIFY wParam = 0; // not used; must be zero lParam = 0; // not used; must be zero
This message has no parameters.
If the content of edit control has been modified, the return value is TRUE; otherwise, it is FALSE.
Windows maintains an internal flag indicating whether the content of the edit control has been changed. This flag is cleared when the edit control is first created; alternatively, an application can send an EM_SETMODIFY message to the edit control to clear the flag.