A turtle plastron showing drilled chisel and burn pits to create cracks for divinations Inscription recording an eventˇXA Shang king had the record of a hunt inscribed on the skull of a deer.

Oracle bone inscriptions are among China's earliest known writings. Their subject matter is composed primarily of "pu-ts'u" (divinatory words), that is, the records of Shang royal divinations. There are also a number of inscriptions that record events. Shang royal divinations touched on almost every topic of importance at the time, such as what to sacrifice in worship to the gods or ancestors, whether it would rain on a particular day, whether the harvest would be good, whether it would be safe to go to war or out hunting, the nature of good and bad omens envisioned in illness and dreams, the timing of childbirth, and the prediction of good fortune or disasters yet to come.           The practice of divination by Shang kings generally involved the official diviner drilling indentations into the reverse side of a turtle shell or cattle bone and then burning the indentations to cause cracks, called "chao" (signs), to appear on the other side. On the basis of these cracks, omens or information were determined.           After completing the divination, the time, name of the diviner, question asked, determination of the omen or information, and whether it came true, were often engraved on the shell or bone, either beside the cracks or on the reverse.           These form the basis of what are known as oracle bone inscriptions. In addition to recording the practice of divination, sometimes events unconnected with sacrificial worship were also recorded on turtle shells or animal bones. Nevertheless, the name "chia-ku wen" (oracle bone inscriptions) is used to refer to both divinatory inscriptions and event records.