Complex sentence: Originally it was identical to GB 2312, and expanded to cover most part of GBK with the release of Windows 95; now superseded by Code page 54936 (GB 18030), but is still prevalent in use.
Split into simpler sentences: Originally it was identical to GB 2312, and expanded to cover most part of GBK with the release of Windows 95. It was superseded by Code page 54936 (GB 18030), but was still prevalent in use.