freepascal.compiler/docs/go32ex/softint.pas

{ Executes a real mode software interrupt

Exactly the interrupt call to get the DOS version.

get DOS version Int 21h / function 30h
Input:
	AH = $30
	AL = $1
Return:
	AL = major version number
	AH = minor version number
}

uses
	go32;

var
	r : trealregs;

begin
	r.ah := $30;
	r.al := $01;
	realintr($21, r);
	Writeln('DOS v', r.al,'.',r.ah, ' detected');
end.