procedure TForm1.Button1Click(Sender: TObject);
var
s1,s2:String;
begin
s1:='ABSA';
s2:='ABSALON';
if EsPrefijo(s1,s2) then
ShowMessage('Son iguales');
end;
Function EsPrefijo(cPref,cCadena:String):Boolean ;
begin
if CompareStr(cPref, Copy(cCadena,1,Length(cPref))) = 0 then
Result:=True
else
Result:=False;
end;