Absolute Routine
 ----------------------------------------------------------------------------


 Action

 Transfers control to a machine-language procedure.


 Syntax

  CALL  Absolute (- argumentlist,-  integervariable%)


 Remarks

 The  Absolute routine uses the following arguments.

-----------------------------------------------------------------------------
 Argument                                Description
 ----------------------------------------------------------------------------
  argumentlist                           Arguments passed to a
                                         machine-language procedure as
                                         offsets (near pointers) from the
                                         current data segment. Although
                                         arguments are passed as offsets,
                                         the machine-language program is
                                         invoked with a far call.

  integervariable%                       The offset from the current code
 Argument                                Description
 ----------------------------------------------------------------------------
  integervariable%                       The offset from the current code
                                         segment, set by  DEF SEG, to the
                                         starting location of the procedure.
                                         The argument  integervariable% is
                                         not passed to the procedure. Your
                                         program may need to execute a  DEF
                                         SEG statement before executing
                                         Absolute to set the code segment
                                         for the called routine. Using a
                                         noninteger value for
                                         integervariable% produces
                                         unpredictable results.






 Note

 The  Absolute routine is provided to maintain compatibility with earlier
 versions of BASIC. Mixed-language programming using the  CALL and  DECLARE
 statements provides a simpler way to use assembly language with BASIC.

 When using the  Absolute routine in OS-2 protected mode, be careful not to
 refer to an illegal memory address. Before it executes the  Absolute
 routine, BASIC attempts to get an executable-code-segment alias for the code
 you wish to access. If this operation fails, BASIC generates the error
 message Permission denied. A safe place to store user-written machine code
 is in memory allocated for a conventional BASIC object, such as an array.

 To use the  Absolute routine in the QBX environment, use the QBX.QLB Quick
 library.

 To use the  Absolute routine outside of the QBX environment, link your progra
 with the QBX.LIB file.

 The QBX.BI header file contains the necessary declarations for the  Absolute
 routine.


 Basica

 Assembly-language programs that are invoked from BASICA and that have string
 arguments must be changed, because string descriptors are now 4 bytes long.
 For a near-string descriptor, the 4 bytes are the low byte and high byte of
 the string length, followed by the low byte and high byte of the string
 address. Far-string descriptors also are 4 bytes long, but their structure
 is proprietary. For more information on using far-string descriptors, see
 Chapter 12, "Mixed-Language Programming" and Chapter 13, "Mixed-Language
 Programming with Far Strings" in the  Programmer's Guide.


 See Also

 CALL, CALLS Statements (Non-Basic)


 Example

 The following example uses  Absolute to execute a machine-language program
 stored in an array. The program indicates whether a math coprocessor is
 installed.

 CONST nASMBYTES = 14
 DEFINT A-Z
 DIM AsmProg(1 TO (nASMBYTES - 2))

 ' The machine-language program stored as data to read into the array.
 AsmBytes.
 DATA &H55  . ' PUSH BPSave base pointer.
 DATA &H8B, &HEC. ' MOV  BP,SP Get our own.
 DATA &HCD, &H11. ' INT  11HMake the ROM-BIOS call.
 DATA &H8B, &H5E, &H06. ' MOV  BX,[BP+6]Get argument address.
 DATA &H89, &H07. ' MOV  [BX],AXSave list in argument.
 DATA &H5D  . ' POP  BPRestore base pointer.
 DATA &HCA, &H02, &H00. ' RET  2Pop argument off stack
 'and make far return.

 ' Poke the machine-language program into the array.
 P = VARPTR(AsmProg(1))' Get the starting offset of the array.
 DEF SEG = VARSEG(AsmProg(1)) ' Change the segment.
 FOR I = 0 TO nASMBYTES - 1
 READ J
 POKE (P + I), J
 NEXT I

 ' Execute the program. The program expects a single integer argument.
 CALL Absolute(X%, VARPTR(AsmProg(1)))
 DEF SEG' Restore the segment.
 ' X% now contains bit-encoded equipment list returned by the system.
 ' Mask off all but the coprocessor bit (bit 2).
 CoProcessor = X% AND &H2
 IF CoProcessor = 2 THEN
 PRINT "Math coprocessor present."
 ELSE
 PRINT "No math coprocessor."
 END IF