What is the output of this code? float x = 5 / 2; printf("%f", x);

The correct answer is B: 2.000000. 5/2 performs integer division (both operands are int), resulting in 2. This is then converted to float as 2.0.

Which memory allocation technique provides better locality of reference for accessing array elements?

The correct answer is B: Single malloc for contiguous array. Contiguous allocation places array elements next to each other in memory, improving cache hits and CPU performance through spatial locality.

In C, what is the purpose of the return statement in a void function?

The correct answer is C: To exit the function immediately without returning a value. In void functions, return statement (without value) can be used to exit the function prematurely. It's optional at the end since function exits automatically.

Which of the following correctly allocates memory for 10 integers?

The correct answer is B: int *p = malloc(10 * sizeof(int));. malloc requires the size in bytes. For 10 integers, we need 10 * sizeof(int) bytes.

What will be the output of sizeof(union test) if union has members: int a, char b, float c?

The correct answer is A: 4 bytes. Union size equals the size of its largest member. Here, both int and float are 4 bytes (largest), so sizeof(union test) = 4 bytes.

Home

Home › Subjects › C Programming › File Handling

C Programming
File Handling

C language from basics to advanced placement prep

21 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 21

Topics in C Programming

All Basics & Syntax 86 Data Types & Variables 97 Control Flow 100 Functions 99 Arrays & Strings 100 Pointers 99 Structures & Unions 100 File Handling 100 Dynamic Memory 98 Preprocessor 99

Q.1 Hard File Handling

In a program that processes binary files with variable-length records, what could cause fread() to return fewer items than requested without reaching EOF?

A A read error occurred during I/O operation

B The file is opened in text mode instead of binary mode

C The buffer size is larger than remaining file size

D All of the above

Correct Answer: D. All of the above

EXPLANATION

fread() can return fewer items due to: (A) I/O errors, (B) text mode conversions affecting byte count, or (C) insufficient data remaining. For robust code, check ferror() and feof() after fread() returns less than requested.

Test

Q.2 Hard File Handling

For implementing a file locking mechanism in a competitive exam environment, which approach correctly handles concurrent file access in POSIX systems?

A Using flock() or fcntl() system calls with F_WRLCK

B Opening file in 'a' mode ensures automatic locking

C Using fseek() to check if file is accessible

D Creating a separate lock file and checking its existence

Correct Answer: A. Using flock() or fcntl() system calls with F_WRLCK

EXPLANATION

flock() and fcntl() with F_WRLCK provide kernel-level file locking in POSIX systems. Option B is false, option C doesn't provide locking, and option D is unreliable due to race conditions.

Test

Q.3 Hard File Handling

A program reads serialized objects using fread(). What's the primary risk when file format changes between versions?

A fread() will fail silently

B Buffer overflow or misaligned struct interpretation

C File size becomes invalid

D Automatic version detection prevents issues

Correct Answer: B. Buffer overflow or misaligned struct interpretation

EXPLANATION

Changed file format causes struct misalignment, leading to buffer overflow or garbage data. No automatic detection in C. Need version headers or checksums.

Test

Q.4 Hard File Handling

When implementing a log file writer with concurrent access, what's the critical issue with standard fopen()?

A fopen() is too slow

B No built-in file locking mechanism

C fopen() doesn't support append atomically

D Memory leaks after multiple opens

Correct Answer: B. No built-in file locking mechanism

EXPLANATION

Standard C fopen/fwrite lack file locking. Multiple processes can corrupt data. Need OS-specific locking (flock/fcntl on Unix) or use 'a' mode with small writes.

Test

Q.5 Hard File Handling

For competitive exam file validation: A 2GB file must be processed without loading entirely in memory. Which strategy is optimal?

A Read entire file into heap-allocated buffer

B Use mmap() for memory-mapped I/O

C Read in fixed-size chunks in loop

D Use external sorting tools

Correct Answer: C. Read in fixed-size chunks in loop

EXPLANATION

Fixed-size chunk processing is standard for large files. mmap() helps but may not be portable. Loading entire file exhausts memory. External tools bypass C programming.

Test

Q.6 Hard File Handling

A program processes encrypted binary data with fread(). Why might using 'r' mode instead of 'rb' cause corruption?

A Text mode converts line endings, corrupting binary data

B Text mode stops at null bytes

C Text mode is slower

D Text mode reduces buffer size

Correct Answer: A. Text mode converts line endings, corrupting binary data

EXPLANATION

Text mode on Windows converts CRLF to LF and vice versa, corrupting binary. Binary mode preserves exact bytes. Null byte handling is secondary concern.

Test

Q.7 Hard File Handling

What does rewind(fp) accomplish compared to fseek(fp, 0, SEEK_SET)?

A rewind() is faster

B rewind() also clears error indicators; fseek() doesn't

C They are functionally identical

D fseek() works only in binary mode

Correct Answer: B. rewind() also clears error indicators; fseek() doesn't

EXPLANATION

rewind(fp) resets pointer AND clears EOF/error flags. fseek(fp, 0, SEEK_SET) only repositions. rewind is essentially: fseek(...); clearerr(...);

Test

Q.8 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.

Test

Q.9 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.

Test

Q.10 Hard File Handling

A program processes a file with multiple reading and writing operations without closing/reopening. What is a potential issue with file buffering?

A Data written to buffer may not be physically written to disk until fflush() or fclose()

B File pointer position becomes unreliable

C Read operations always return cached data from memory

D File automatically truncates after buffer fills

Correct Answer: A. Data written to buffer may not be physically written to disk until fflush() or fclose()

EXPLANATION

File I/O uses buffering for efficiency. Data in write buffer stays in memory until fflush(fp) explicitly flushes or fclose() is called, risking data loss if program crashes.

Test

1 2 3

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

C Programming File Handling

C Programming
File Handling