What does IDYES mean?

Below I have the program in question's source code listed.

Now I see that for the cd player to open on your computer when you run it, you have to answer the message box "YES", and assembly language compares the message box with what you entered to see if the program will continue. With a little bit of research IDYES obviously has something to do with basic/message-box. But what?

Thanks

Code:

; Beer - example of tiny (one section) Win32 program

format PE GUI 4.0

include 'win32a.inc'

; no section defined - fasm will automatically create .flat section for both
; code and data, and set entry point at the beginning of this section

        invoke  MessageBoxA,0,_message,_caption,MB_ICONQUESTION+MB_YESNO
        cmp     eax,IDYES
        jne     exit

        invoke  mciSendString,_cmd_open,0,0,0
        invoke  mciSendString,_cmd_eject,0,0,0
        invoke  mciSendString,_cmd_close,0,0,0

exit:
        invoke  ExitProcess,0

_message db 'Do you need additional place for the beer?',0
_caption db 'Desktop configuration',0

_cmd_open db 'open cdaudio',0
_cmd_eject db 'set cdaudio door open',0
_cmd_close db 'close cdaudio',0

; import data in the same section

Edit by revolution: Added code tags