举例:
var
  ss,s: string;
  i: Integer;
begin
  ss := 'CodeGear Delphi 2007';
  s := 'Gear';
  i := Pos(s,ss);
  ShowMessage(IntToStr(i));  {5}

  s := '2008';
  i := Pos(s,ss);
  ShowMessage(IntToStr(i));  {0}
end;
System 单元下的公用函数目录