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Inside Macintosh: Operating System Utilities /

Chapter 9 - Start Manager / Start Manager Reference

Routines / Identifying and Setting the Default Startup Device

GetDefaultStartup

You can use the GetDefaultStartup procedure to return information about the default startup device.

PROCEDURE  GetDefaultStartup (paramBlock: DefStartPtr);

paramBlock

A pointer to a default startup device parameter block.

<--	sdExtDevID	SignedByte	External device ID.
<--	sdPartition	SignedByte	Reserved.
<--	sdSlotNum	SignedByte	Physical slot number.
<--	sdSRsrcID	SignedByte	Slot resource ID (SResourceID).
<--	sdReserved1	SignedByte	Reserved.
<--	sdReserved2	SignedByte	Reserved.
<--	sdRefNum	Integer	Driver reference number.

DESCRIPTION

The GetDefaultStartup procedure returns information about the default startup device from parameter RAM. The default startup device parameter block of data type DefStartType defines two kinds of startup devices: either a slot or a SCSI device. The GetDefaultStartup procedure returns in the sdRefNum field a value indicating the startup device type. A negative value indicates a SCSI device. A positive value indicates a slot device. If the value is negative, the sdRefNum field contains the driver reference number needed to identify that device. If the value is positive, the slotDev variant of the default startup device parameter block contains information about the slot device.

You cannot read the system's default startup device parameter block directly. Instead, create another parameter block to which the GetDefaultStartup procedure can write and pass GetDefaultStartup a pointer to that parameter block.

ASSEMBLY LANGUAGE INFORMATION

The registers on entry and exit for this routine are

Registers on entry
A0	Address of the default startup device parameter block

Registers on exit
A0	Address of the default startup device parameter block

SEE ALSO

For more information about the default startup device parameter block
see "The Default Startup Device Parameter Block" beginning on page 9-18.

To specify the default startup device, see the description of the SetDefaultStartup procedure described next.