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Inside Macintosh: Operating System Utilities /

Chapter 7 - Parameter RAM Utilities / Parameter RAM Utilities Reference

Routines /

GetSysPPtr

You can use the GetSysPPtr function to obtain a pointer to the low-memory copy of parameter RAM.

FUNCTION GetSysPPtr: SysPPtr;

DESCRIPTION

The GetSysPPtr function returns a pointer to the low-memory copy of parameter RAM. The copied parameter RAM values are accessible through the system parameters record.

You can examine the values stored in the various fields of this record, or you can change them and call the WriteParam function to copy your changes back into parameter RAM.

SPECIAL CONSIDERATIONS

Because of the organization of parameter RAM is subject to change, you should not use the GetSysPPtr function to change the values in parameter RAM. Instead use the appropriate Toolbox routines to modify values in parameter RAM.

ASSEMBLY-LANGUAGE INFORMATION

The global variable SysParam contains the address of the start of the system parameters record. Other global variables allow you to access individual fields of the system parameters record directly. These global variables all begin with the letters SP and point directly into the system parameters record stored in low memory. Other global variables referencing memory locations outside of the system parameters record are used to store copies of individual fields of the system parameters record.

SEE ALSO

For information about the system parameters record, see page 7-31. For a list of global variables associated with the system parameters record, see "Global Variables" on page 7-38. The WriteParam function is described next.