In September 1998, the first version for Windows was released as 'Sibelius', with the version number reset to 1.0. A Mac version 1.2 was released a few months later, and the company thereafter used conventional version numbers for both platforms across subsequent upgrades. Scores created on one platform could be opened on the other, and were backward compatible. To produce these versions, the software was completely rewritten in C++, while retaining most of the original's functionality and user interface with numerous enhancements. The original Acorn names 'Sibelius 6' and 'Sibelius 7' were later re-used to denote versions 6 and 7 of Sibelius for Windows/Mac.