Acknowledges the close state of the internal close flag.
mov ah, 16h ; Windows multiplex function
mov al, 8Fh ; VM Close
mov dh, 2 ; Acknowledge Close
mov dl, 0 ; always 0
int 2Fh
or ax, ax
jz success
Returns zero in the AX register if successful.
Acknowledging the close state is necessary if an application needs to perform additional keyboard input before exiting. If the close state has been signaled but not yet acknowledged by an application, all keyboard read operations will return NULL and buffered line input will return an empty string.