C Programming — File Handling Questions & Answers

Q.21 Medium File Handling

A program reads struct records using fread(). After reading 100 records of 64 bytes each, what is the total bytes read if successful?

A 100

B 64

C 6400

D fread() doesn't return bytes, only count

Correct Answer: C. 6400

EXPLANATION

fread(ptr, 64, 100, fp) reads 100 items of 64 bytes each = 6400 bytes total. fread() returns count of items read, not bytes.

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Q.22 Medium File Handling

What happens if you call fclose() on an already closed file pointer?

A Returns 0

B Returns EOF and may cause undefined behavior

C Silently succeeds

D Raises compile-time error

Correct Answer: B. Returns EOF and may cause undefined behavior

EXPLANATION

Calling fclose() on closed file causes undefined behavior and returns EOF. This is a runtime issue, not compile-time.

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Q.23 Medium File Handling

A program needs to append 500 integers to an existing binary file. Which combination is correct?

A fopen(file, 'ab') with fwrite()

B fopen(file, 'a') with fprintf()

C fopen(file, 'ab') with fprintf()

D fopen(file, 'wb') with fwrite()

Correct Answer: A. fopen(file, 'ab') with fwrite()

EXPLANATION

Binary append requires 'ab' mode with fwrite(). Option B uses text mode. Option D would overwrite. Option C mixes binary mode with text function.

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Q.24 Easy File Handling

Which mode opens file in text format with write permission only?

A wb

B w

C wt

D wa

Correct Answer: B. w

EXPLANATION

'w' mode opens file in text format for writing. 'wb' is binary write. 'wt' is explicitly text write but 'w' is default text mode.

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Q.25 Easy File Handling

Which function returns the current position of file pointer?

A fgetpos()

B ftell()

C fseek()

D rewind()

Correct Answer: B. ftell()

EXPLANATION

ftell() returns the current file position as a long integer. fgetpos() stores position in a fpos_t structure. rewind() resets to beginning.

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Q.26 Easy File Handling

What does fseek(fp, 0, SEEK_END) accomplish?

A Moves pointer to beginning of file

B Moves pointer to end of file

C Moves pointer to current position

D Closes the file pointer

Correct Answer: B. Moves pointer to end of file

EXPLANATION

SEEK_END moves the file pointer to the end of file. SEEK_SET goes to beginning, SEEK_CUR to current position.

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Q.27 Easy File Handling

Which file opening mode allows both reading and writing without truncating existing content?

A r+

B w+

C a+

D x+

Correct Answer: A. r+

EXPLANATION

Mode 'r+' opens file for reading and writing without truncating. 'w+' truncates the file, 'a+' appends, and 'x+' is for exclusive creation.

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Q.28 Hard File Handling

For reading a configuration file line-by-line where lines may exceed 256 characters, which function is recommended for ISRO/GATE 2024 exams?

A fgets(buffer, sizeof(buffer), fp) with dynamic memory if needed

B fscanf(fp, "%s", buffer) with fixed-size array

C fgetc() in a loop to manually read lines

D fread() to read entire file at once

Correct Answer: A. fgets(buffer, sizeof(buffer), fp) with dynamic memory if needed

EXPLANATION

fgets() is safest for line reading with size protection. For lines exceeding buffer size, use dynamic allocation or getline(). fscanf() with %s is vulnerable to buffer overflow.

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Q.29 Hard File Handling

Which scenario would be most problematic when using fprintf() for data that needs exact binary preservation?

A fprintf() interprets format specifiers and may alter binary data representation

B fprintf() is always safer than fwrite()

C fprintf() cannot handle NULL characters in data

D Both A and C are correct

Correct Answer: D. Both A and C are correct

EXPLANATION

fprintf() is text-oriented and interprets format specifiers, potentially modifying data. It also stops at NULL characters. For binary data, fwrite() is appropriate.

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Q.30 Medium File Handling

A C program must securely close a file and handle potential errors. What is the best approach?

A if(fclose(fp) != 0) { handle_error(); }

B fclose(fp); assuming it always succeeds

C Just let the OS close file when program exits

D Use multiple fclose() calls for safety

Correct Answer: A. if(fclose(fp) != 0) { handle_error(); }

EXPLANATION

fclose() returns 0 on success and EOF (-1) on error. Checking return value ensures buffered data is flushed and handles errors like write failures.

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