Double check 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nf6 5.Qd3 e5 6.dxe5 Qa5+ 7.Bd2 Qxe5 8.0-0-0 Nxe4 9.Qd8+ (sacrificing a queen in order to set up a double check) Kxd8 10.Bg5++ and White mates after 10...Ke8 11.Rd8# or 10...Kc7 11.Bd8#. A double check was also seen in the celebrated Evergreen Game, Anderssen–Dufresne, 1852. Anderssen won with 20.Rxe7+! Nxe7 21.Qxd7+!! (a queen sacrifice to set up a deadly double check) Kxd7 22.Bf5++ Ke8 (or 22...Kc6 23.Bd7#) 23.Bd7+ Kf8 24.Bxe7#. In chess with variant rules or fairy pieces, other ways of delivering a double check may be possible. Triple, quadruple and even quintuple checks may
Quadruple-precision floating-point format the double-double technique above, although that technique does not implement IEEE quadruple precision), since direct hardware support for quadruple precision is, as of 2016, less common (see "Hardware support" below). One can use general arbitrary-precision arithmetic libraries to obtain quadruple (or higher) precision, but specialized quadruple-precision implementations may achieve higher performance. A separate question is the extent to which quadruple-precision types are directly incorporated into computer programming languages. Quadruple precision is specified in Fortran by the codice_2 (module codice_3 from Fortran 2008 must be used, the constant codice_4 is equal to 16 on most processors), or as codice_5, or in