sdOSType
DefOSRec structure
#include <Start.h>
typedef structure { Size Offset Description
char sdReserved; 1 0 Reserved
char sdOSType; 1 1 Default operating system
identification
typedef DefOSRec *DefOSPtr;

Notes: This structure is used in calls to GetOSDefault and SetOSDefault
identify which operating system will be used when the system starts up.