标识符的其他字符必须是字母，数字或下划线。

All other characters in an identifier must be letters, digits, or the underscore.

youdao

缺省情况下，文件结束字符串是下划线(_)；如果将该字符作为单个输入参数来发送，则它之后的所有内容将被忽略。

By default, the end-of-file string is an underscore (_); if that character is sent as a single input argument, everything after it is ignored.

youdao

两者是类似的，但目前的区别在于字母大小写，连接词的使用；例如：连字符或下划线，潜在的附加标签（子标签）类型和编号。

The two are similar, but present differences in letter case, use of connective; e.g. hypen or underscore, and the type and number of possible extra tags (subtags).

youdao