Chinese writing has been known in Korea for over 2,000 years. It was used widely during the Chinese occupation of northern Korea from 108 BC to 313 AD. By the 5th century AD, the Koreans were starting to write in Classical Chinese – the earliest known example of this dates from 414 AD. They later devised three different systems for writing Korean with Chinese characters: Hyangchal(향찰/鄕札), Gukyeol (구결/口訣) and Idu (이두/吏讀). These systems were similar to those developed in Japan and were probably used as models by the Japanese.
The Idu system used a combination of Chinese characters together with special symbols to indicate Korean verb endings and other grammatical markers, and was used to in official and private documents for many centuries. The Hyangchal system used Chinese characters to represent all the sounds of Korean and was used mainly to write poetry.
The Koreans borrowed a huge number of Chinese words, gave Korean readings and/or meanings to some of the Chinese characters and also invented about 150 new characters, most of which are rare or used mainly for personal or place names.