-- card: 66438 from stack: in
-- bmap block id: 50859
-- flags: 0000
-- background id: 4507
-- name: 


-- part 1 (button)
-- low flags: 00
-- high flags: 0000
-- rect: left=29 top=174 right=231 bottom=128
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 1
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: Inheritance structure
----- HyperTalk script -----
on mouseUp
  setCrossReference
  go to card id 67556
end mouseUp




-- part contents for background part 44
----- text -----
Who has control?


Inheritance

-- part contents for background part 2
----- text -----
Message handlers (cont.)

-- part contents for background part 1
----- text -----
HyperCard initially sends system messages to the current card—the mouse button is up or down, the field has been modified, the card has been closed, etc.

HyperCard uses inheritance to determine who is in control at any moment.  If an object's script doesn't have a response for a message, the message goes to the next larger object the first object is a part of—the card the button is on, then the background the card has, etc.  
For example:

The user presses a button named "Fred".

-- part contents for background part 43
----- text -----
267,189