C Programming - MCQ Practice Questions

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.

SEEK_END moves pointer relative to end of file. Offset 0 means go to the exact end. SEEK_SET (beginning) and SEEK_CUR (current) are other origin options.

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.

fscanf() reads formatted data from file (like scanf() but from file). fgets() reads strings. fread() reads binary data. getc() reads single character.

fopen() returns NULL pointer on failure. Proper practice is to check: if(fp == NULL) {...error handling...}. Returning -1 is for system calls like open().

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).

"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.

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.

fflush(fp) forces buffered output to be written to disk immediately without closing the file. Useful for ensuring data safety before risky operations.

Mixing write (fwrite - binary) and read (fprintf - formatted text) functions on same data causes mismatch. Binary data won't have format specifiers; misinterpretation results.

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.

fread() with buffer reads multiple bytes per call, reducing function call overhead. fgetc() makes 100,000 separate calls. fgets() is limited to reading up to newline.

Third parameter is 'whence': SEEK_SET (beginning), SEEK_CUR (current position), SEEK_END (end). Second parameter specifies offset in bytes.

fread(buffer, size, count, fp) efficiently reads file in manageable chunks. Process each chunk, then read next. This is standard practice for large file handling.

stdio.h (Standard Input/Output) contains all file handling functions like fopen(), fclose(), fread(), fwrite(), etc.

'w+' mode opens a file for both reading and writing. If the file doesn't exist, it creates a new one. If it exists, it truncates the file to zero length.

fputc() writes a single character to the specified file. fgetc() reads a character, fwrite() writes blocks, and fprintf() writes formatted output.

feof(fp) returns a non-zero value when EOF (End Of File) is reached, and returns zero when not at EOF.

rewind(fp) repositions the file pointer to the start of the file. It's equivalent to fseek(fp, 0, SEEK_SET).

'a+' mode opens file for reading and appending. New data is added at the end without removing existing content. 'w+' would truncate the file.