Zhuyin fuhao (Chinese: 注音符號; pinyin: Zhùyīn fúhào; Zhuyin Fuhao: ㄓㄨˋ ㄧㄣ ㄈㄨˊ ㄏㄠˋ; literally "phonetic symbols"), often abbreviated as zhuyin and colloquially called bopomofo, is a phonetic system for transcribing Chinese, especially Mandarin. It was introduced in the 1910s.
Consisting of 37 characters and four tone marks, it transcribes all possible sounds in Mandarin. The Wade system was replaced by Hanyu Pinyin in 1958 by the Government of the People's Republic of China, and at the International Organization for Standardization (ISO) in 1982. Although Taiwan officially abandoned Wade-Giles in 2009, Bopomofo is still the official phonetic notation system of the country and remains widely used as an educational tool and electronic input method in Taiwan.
More information on the Wikipedia page .