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 Sixteen Prefectures The Sixteen Prefectures (), more specifically the Sixteen Prefectures of Yan and Yun or the Sixteen Prefectures of You and Ji (), comprise a historical region in northern China along the Great Wall in present-day Beijing and Tianjin Municipalities and northern Hebei and Shanxi Province, that were ceded by the Shatuo Turk Emperor Shi Jingtang of the Later Jin to the Khitan Liao dynasty in 938. The subsequent Later Zhou and Song Dynasties sought to recover the ceded northern territories. Most of the Sixteen Prefectures including the two principal cities, Youzhou (also called Yanzhou, modern Beijing) and Yunzhou