The Code for the Construction and Equipment of Mobile Offshore Drilling Units, 1989 (1989 MODU Code) was adopted by Assembly resolution A.649 (16) and concerns MODUs built since 1 May 1991. The 1989 MODU Code superseded the 1979 MODU Code adopted by Assembly resolution A.414(XI). The Maritime Safety Committee(MSC)adopted amendments to the 1989 MODU Code in May 1991 and decided that, to maintain compatibility with SOLAS, the amendments should become effective on 1 February 1992. Further amendments were adopted in May 1994, to introduce the harmonized system of survey and certification (HSSC) into the Code, provide guidelines for vessels with dynamic positioning systems and introduce provisions for helicopter facilities. The Committee decided that the amendments introducing the HSSC should become effective on the same date as the 1988 SOLAS and Load Line Protocols relating to he HSSC (i.e. 3 February 2000), and that those providing guidelines for vessels with dynamic positioning systems and provisions for helicopter facilities should become effective on 1 July 1994.