What is the name of the special letter, the signs of which were issued on clay tablets?

The oldest writing system, which was often written on clay tablets, is called cuneiform. This writing originated first in southern Mesopotamia. In Sumer, it was used already at the end of the fourth millennium, from where it spread to the north and was borrowed by other civilizations. Large libraries and archives, where cuneiform clay tablets were kept, were found on the territory of the capital of the Assyrian kingdom – Nineveh, as well as in different regions of the Hittite kingdom. Cuneiform was also written on stones and rocks.