Korean is the official language of the country Korea, in both South and North. It is also one of the two official languages in the Yanbian Korean Autonomous Prefecture in People's Republic of China. There are about 78 million Korean speakers worldwide. In the 15th century, a national writing system was commissioned by Sejong the Great, the system being currently called Hangul. Prior to the development of Hangul, Koreans had used Hanja and phonetic systems like Hyangchal, Gugyeol and Idu extensively for over a millennium. However, it was not until the 20th century that Hangul became the dominant national script, given the yangban class' preference of the Hanja system.