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Inside Macintosh: Operating System Utilities /

Chapter 9 - Start Manager / Start Manager Reference

Data Structures

The Default Startup Device Parameter Block

Two procedures, GetDefaultStartup and SetDefaultStartup, use the default startup device parameter block. You can use these procedures and the default startup device parameter block to get or set the default startup device. As defined by the DefStartType data type, a startup device is either a slot or a SCSI device. The DefStartRec data type defines the default startup device parameter block.

TYPE  DefStartType = (slotDev, scsiDev);
      
      DefStartRec = 
RECORD
   CASE DefStartType OF
      slotDev:
         sdExtDevID: SignedByte; {external device ID}
         sdPartition:SignedByte; {reserved}
         sdSlotNum:  SignedByte; {slot number}
         sdSRsrcID:  SignedByte; {SResourceID}
      scsiDev:
         sdReserved1:SignedByte; {reserved}
         sdReserved2:SignedByte; {reserved}
         sdRefNum:   Integer;    {driver reference number}
END;
DefStartPtr = ^DefStartRec;

Field Description

sdExtDevID

The external device ID specified by a slot's driver. This ID identifies one of perhaps several devices connected through a single slot.

sdPartition

Reserved.

sdSlotNum

A number that identifies the location of the NuBus slot containing the default startup card. (Currently, these numbers range from $9 through $E on six-slot computers.)

sdSRsrcID

The resource ID (SResourceID) for the slot.

sdReserved1

Reserved.

sdReserved2

Reserved.

sdRefNum

A negative value in this field indicates the driver reference number for a SCSI device. A positive number indicates a slot device, in which case the fields in the slotDev variant.