What must be specified when opening a file in TEXT MODE in a Unicode system?

When opening a file in TEXT MODE on a Unicode system, it is essential to specify the byte order because Unicode can encode characters using different byte orders, particularly in UTF-16 and UTF-32 formats. The byte order indicates how the multibyte characters are represented within the file, with options such as big-endian or little-endian. This specification ensures that the system properly interprets the character encodings, preventing misinterpretation of the data.

Understanding byte order is crucial for correctly reading and writing text files, especially when dealing with characters outside the basic ASCII range. By specifying the byte order, developers safeguard against errors that could arise from mismatches between the file's encoding and how it is accessed or displayed within the system.

Other options, while related to file encoding and text processing, are not as fundamental to the act of opening a file in text mode on a Unicode system as the byte order requirement. For instance, while encoding does play a role in how text data is preserved and represented, the core requirement in this context is primarily tied to byte order for ensuring accurate interpretation of the data.