操作函数是 UNICODE的还是 非UNICODE 的来决定。(,ccs=string
The given string is taken as the name of a coded character set and the stream is marked as wide-oriented. Thereafter, internal conversion functionsconvert I/O to and from the character setstring. If the ,ccs=string syntax is not specified, then the wide-orientation of the stream isdetermined by the first file operation. If that operation is a wide-character operation, the stream is marked wide-oriented, and functions to convert to thecoded character set are loaded. )