A printing press is a device that allows for the mass production of uniform prints, primarily in the form of books, brochures and newspapers. In the 15th century, the press was founded in China, where revolutionary social changes took place and further development in Europe. No one knows when the first press was invented, and no one knows who invented it, but the oldest known printed text is the diamond scripture that originated in China in the year of AD, one from Buddhist books in Dunhuang, China, date back to around 868 AD. The Tang Dynasty is said to be the oldest printed book known. Diamonds are created in a way called block printing, which uses a panel of hand-carved wood blocks for reverse printing. Dunhuang also has other texts, including print calendars around 877 AD, mathematical charts, vocabulary guidance, etiquette guidance, funeral and wedding guides, educational materials for children, dictionaries and almanacs. It was during this period of early printing that the volume began to be replaced by text in book format. At that time, Japan and South Korea also used woodblock printing, and metal prints were developed during this period, mainly for Buddhist and Taoist texts.