Seven-segment display letter to be unambiguous, merely for the words as a whole to be readable. Similar displays with fourteen or sixteen segments are available allowing less-ambiguous representations of the alphabet. Using a restricted range of letters that look like (upside-down) digits, seven-segment displays are commonly used by school children to form words and phrases using a technique known as "calculator spelling". Seven-segment display A seven-segment display (SSD), or seven-segment indicator, is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot matrix displays. Seven-segment displays are widely used in digital clocks, electronic
Sixteen Prefectures based in modern-day Beijing commanded 11 of the Sixteen Prefectures. The other seven were commanded by the Hedong Commandery based in Yunzhou, modern Datong. The historian Frederick W. Mote writes that there were actually 19 prefectures but does not specify them. Chinese historians do not consider Yíngzhou (营州; modern Qian'an, Hebei) and Pingzhou (平州; modern Lulong, Hebei) to be part of the Sixteen Prefectures because they had already been occupied by the Khitans during the Later Tang, prior to Shi Jingtang’s cession. Yizhou (易州; modern Yi County, Hebei), which fell to the Khitans after the cession, is also excluded from