Before using hanyu pinyin, China used a pinyin called "Witoma" to mark Chinese characters. Because the Chinese characters read are inaccurate, such as Peking = Beijing = Beijing; Later, I changed to a new Chinese pinyin, which is the one I use now. Tsinghua = Tsinghua = Tsinghua.

Peking University and Tsinghua are world famous schools, and they can use the old Pinyin, so they use the abbreviations PKU and TSU. PKU = Peking University; TSU = Tsinghua University