Govt. Exams
Entrance Exams
fgets(buffer, size, fp) safely reads up to (size-1) characters or until newline from file fp, preventing buffer overflow. fscanf() is vulnerable to overflow.
ftell(fp) returns the current position of the file pointer (in bytes) from the beginning of the file. Returns -1L on error.
'a+' mode opens file for reading and appending. New data is added at the end without removing existing content. 'w+' would truncate the file.
In append mode "a" or "a+", file pointer initially points to end of file for writing. For reading in "a+", you must explicitly seek to read from start.
fflush(fp) forces buffered output to be written to disk immediately without closing the file. Useful for ensuring data safety before risky operations.
Best solution is allocate larger buffer. If line is 500 chars, use buffer >= 501. Option C partially works but complicates newline handling. fscanf() doesn't automatically handle long lines.
"w" mode opens file for writing and truncates it to zero length if it exists. "r+" doesn't truncate. "a" and "a+" are append modes that don't truncate.
To skip first 10 structures and read 11th: 10 * 32 = 320 bytes from start. Option B (320 bytes) positions pointer at start of 11th structure (320 bytes offset).
Without fclose() or fflush(), buffered data remains in memory. If program terminates, that data never reaches disk. System may flush on exit but it's unreliable.
In text mode, fseek() behavior is implementation-dependent due to line-ending conversions (\r\n vs \n). Binary mode provides more predictable fseek() behavior with absolute byte positions.
