C standard I/O library: what does rewind(stream) do to a file stream? Choose the most accurate behavior per ISO C for a valid open stream.

Introduction / Context:The function rewind(stream) is part of the C standard I/O library. This question tests understanding of file positioning and status flags for streams opened via fopen or related functions.

Given Data / Assumptions:

• stream is a valid FILE* opened earlier.
• We are using ISO C semantics for rewind.
• Error and end-of-file indicators may have been set previously.

Concept / Approach:

rewind(stream) moves the file position indicator to the beginning of the file and clears both the error and end-of-file indicators for that stream. It does not return a value. This contrasts with functions like fseek/fseeko which return status codes and can position relative to various origins.

Step-by-Step Solution:

Verification / Alternative check:

Behavior mirrors fseek(stream, 0, SEEK_SET) followed by clearerr(stream), but rewind is the concise, standardized helper for this common action.

Why Other Options Are Wrong:

Character reverse: There is no such notion in standard C I/O.

End of file: rewind goes to the start, not the end.

Beginning of that line: Line concepts are not known to the stream positioning API.

Common Pitfalls:

• Forgetting that rewind also clears EOF and error indicators.
• Expecting a return value to signal success or failure.

Final Answer:

Reposition the file pointer to beginning of file.