freepascal.compiler/docs/go32ex/flags.pas

{ 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.