There are two types of stream orientation for input and output, a wide-character (wchar_t) oriented and a byte (char) oriented. A stream is without orinetation after that stream has been associated with a file, until an operation occurs.

Once any operation is performed on that stream, that stream becomes oriented by that operation to be either byte oriented or wide-character oriented and remains that way until the file has been closed and reopened.

The byte oriented functions are: fgetc, fgets, fprintf, fputc, fputs, fread, fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts, scanf, ungetc, vfprintf, vfscanf, and vprintf. The wide-character oriented functions are discussed in "wchar.h," describing wchar.h.

After a stream orientation is established, any call to a function of the other orientation is not applied. That is, a byte-oriented input/output function does not have an effect on a wide-oriented stream.