underbar
美
英 
例句
Do not use _ (underbar) as the first character of a name.
不要把_(下划线)作为变量名的第一个字符。
Names should be formed from the 26 upper and lower case letters (A . . Z, a . . z), the 10 digits (0 . . 9), and _ (underbar).
变量名应由26个大小写字母(A..Z,a..z),10个数字(0..9),和_(下划线)组成。