shang 陰上: is the "thanh hỏi as it is called today. dương thượng or yang shang 陽上: is the "thanh ngã as it is called today. Âm khứ or yin qu 陰去: is the tone "thanh sắc" in words that, when written in the Quốc ngữ script, do not end with one of the four letters "c", "ch", "p", "t". Dương khứ or yang qu 陽去: is a "thanh nặng" in words that, when written in the Latin script, do not end with one of the four letters "c", "ch", "p", "t". âm nhập or yin ru 陰入: is the "thanh sắc" in words that, when written in the Latin script, end with one of the four letters "c", "ch", "p", "t". "Dương nhập or yang ru" 陽入: is a heavy bar in words that, when written in national language, end with one of the four letters "c", "ch", "p", "t". Tones of "âm/yin" degree are marked with a small semi-circle, and tones of "dương/yang" degree are marked with a small circle mark. To indicate serenity, the tone is placed next to the "left foot" of the word, with the bar mark placed next to the "left shoulder" of the word, with the accent bar placed next to the "right shoulder" of the text, with the accent bar placed next to the "right foot" of the text. Quoc Am Tan Tu can be written vertically or horizontally like Han characters and Nom characters, and is a set of phonetic scripts created by the Vietnamese themselves (when Chu Nom is a logographic created by the Vietnamese, Quoc Ngu is a phonetic script created by a foreigner). Unfortunately, when Quoc Am Tan Tu was born, it didn't have enough time to be completed and popularized like Kana in Japan, because the political and social situation of Vietnam was too complicated at that time due to the gradual weakening of Nguyen rule and the beginning of the French invasion. Chữ Quốc ngữ Vietnamese in Latin script, called Chữ quốc ngữ, is the currently-used script. It was first developed by Portuguese missionaries in the 17th century, based on the pronunciation of Portuguese language and alphabet. For 200 years, chu quoc ngu was mainly used within the Catholic community. However, during French administration, the alphabet was further modified and then later made a part of compulsory education in 1910. Meanwhile, the use of classical Chinese