freepascal.compiler/docs/go32ex/flags.pas

{ example for :
          realintr()
          flags constants
          trealregs record
}
{ This example demonstrates the use of the flag constants in conjunction with
  an interrupt call

  In detail it checks if APM (advanced power management) is available.

  Int 15h 5300h - APM specification : Installation check
  Input : AX = 5300h
          BX = device id of system BIOS (= 0000h)
  Return : Carry clear if successful
           AH = major version (BCD)
           AL = minor version (BCD)
}

uses go32;

var r : trealregs;

begin
     { set register values and issue real mode interrupt call }
     r.ax := $5300;
     r.bx := 0;
     realintr($15, r);
     { check if carry clear and write a suited message }
     if ((r.flags and carryflag)=0) then begin
        Writeln('APM v', (r.ah and $f), '.', (r.al shr 4), (r.al and $f), ' detected');
     end else
         Writeln('APM not present');
end.