A program uses fprintf() to write 1000 integers to a file but doesn't call fclose(). What could happen?

The correct answer is B: Data in buffer may be lost if program terminates. 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.

What is the output of this complex nested control flow? int x = 1, y = 2; if (x < y) { x++; y--; if (x == y) printf("Equal"); else printf("NotEqual"); }

The correct answer is A: Equal. x=1, y=2. Since 1 < 2, x becomes 2 and y becomes 1. Now x != y, but after operations x=2, y=1. Wait: x++ makes x=2, y-- makes y=1. So x==y is false, printing 'NotEqual'. Rechecking: 1 < 2 is true, so enter if. x becomes 2, y becomes 1. 2 == 1 is false, so else executes, printing 'NotEqual'.

Which of the following statements about structures is TRUE?

The correct answer is B: A structure is a collection of variables of different data types grouped under a single name. A structure allows grouping of different data types. Padding may be added by the compiler for alignment.

Consider the following code: #define MAX 100 #define MAX 200 What will be the result?

The correct answer is A: Compilation error: macro redefinition. In C, redefining a macro without #undef first will cause a compilation error. Most compilers treat macro redefinition as an error.

What is the output? int x = 5; switch(x) { case 5: printf("Five"); case 6: printf("Six"); default: printf("Default"); }

The correct answer is B: FiveSixDefault. Without a break statement after case 5, control falls through to case 6 and default. This is called fall-through behavior in switch statements.

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 11–20 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.11 Hard File Handling

When writing binary structures with fwrite(), which precaution is essential for portability across different systems?

A Account for struct padding and alignment differences

B Always use text mode instead of binary

C Ensure file size matches sizeof(struct) * count

D Use network byte order for all integers

Correct Answer: A. Account for struct padding and alignment differences

EXPLANATION

Struct padding varies by architecture and compiler. Binary files written on one system may not read correctly on another due to different alignment. Use serialization techniques for portability.

Test

Q.12 Hard File Handling

How can you determine the size of a file in bytes using standard C functions?

A Use fseek(fp, 0, SEEK_END) followed by ftell(fp)

B Use stat() function on the filename

C Use fstat() on the file descriptor

D All of the above methods work

Correct Answer: D. All of the above methods work

EXPLANATION

Multiple methods exist: fseek/ftell repositions and returns position, stat() gets file info including size, and fstat() does similar with file descriptor. All are valid.

Test

Q.13 Hard File Handling

A large binary file of 10GB is being processed. Reading entire file into memory is impossible. Which approach is best?

A Use fread() to read file in chunks, process each chunk

B Use multiple fopen() calls on same file

C Split file manually into smaller files

D Use fscanf() which has built-in chunking

Correct Answer: A. Use fread() to read file in chunks, process each chunk

EXPLANATION

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.

Test

Q.14 Hard File Handling

A program uses fgetc() to read 100,000 characters from a file sequentially. Which alternative would be more efficient?

A Use fgets() with larger buffer

B Use fread() with appropriate buffer size

C Use fscanf() with %c format

D Continue with fgetc(); efficiency doesn't matter

Correct Answer: B. Use fread() with appropriate buffer size

EXPLANATION

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.

Test

Q.15 Hard File Handling

A program writes binary data using fwrite() but reads it back with fprintf(). What will happen?

A Data will be read correctly

B Binary data will be misinterpreted; text formatting won't apply

C Program will crash

D Only null bytes will be read

Correct Answer: B. Binary data will be misinterpreted; text formatting won't apply

EXPLANATION

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

Test

Q.16 Hard File Handling

What is the purpose of using fflush() in file handling, and when is it critical to use it?

A To move file pointer to the beginning of the file

B To write buffered data to the actual file on disk

C To close the file gracefully

D To clear error flags from the stream

Correct Answer: B. To write buffered data to the actual file on disk

EXPLANATION

fflush() writes any buffered data to the underlying file. It's critical when you need to ensure data is written to disk before continuing, especially before reading the same file.

Test

Q.17 Hard File Handling

A program writes data using fprintf() and later attempts to read it back. However, the read operation fails intermittently. What could be the most likely cause?

A fprintf() is not suitable for output operations

B The buffer was not flushed before reading, causing incomplete data

C The file was opened in binary mode instead of text mode

D The file pointer was not reset after writing

Correct Answer: B. The buffer was not flushed before reading, causing incomplete data

EXPLANATION

fprintf() buffers output. Without flushing (fflush() or fclose()), subsequent read operations may see incomplete data. This is a common source of bugs.

Test

Q.18 Hard File Handling

Consider using fseek() on a file opened in text mode with SEEK_END and a non-zero offset. What is the standard behavior?

A It is guaranteed to work correctly on all platforms

B It is undefined behavior and may not work correctly on all platforms

C It always returns an error

D It works only on Windows systems

Correct Answer: B. It is undefined behavior and may not work correctly on all platforms

EXPLANATION

In text mode, fseek() with non-zero offset relative to SEEK_END is undefined behavior. Use fseek(fp, 0, SEEK_END) for reliable behavior.

Test

Q.19 Hard File Handling

In a program reading a binary file of 1000 integers, fread() is called as: fread(arr, sizeof(int), 1000, fp). If only 500 integers are present, what will fread() return?

A 500

B An error code

C NULL

D The bytes read (typically 2000)

Correct Answer: A. 500

EXPLANATION

fread() returns the number of complete items successfully read, not the number of bytes. It will return 500 even if 1000 were requested.

Test

Q.20 Hard File Handling

Which of the following correctly implements appending to a file?

A FILE *fp = fopen("file.txt", "a");

B FILE *fp = fopen("file.txt", "w");

C FILE *fp = fopen("file.txt", "r+");

D FILE *fp = fopen("file.txt", "ab+");

Correct Answer: A. FILE *fp = fopen("file.txt", "a");

EXPLANATION

Mode "a" opens a file for appending. New data is written at the end of the file. Mode "w" truncates the file, "r+" requires file to exist, "ab+" is appending in binary with both read/write.

Test

1 2 3

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

C Programming File Handling

C Programming
File Handling