Which mode should be used if you want to read and write to a file without truncating existing content?

The correct answer is B: "r+". The 'r+' mode opens a file for both reading and writing without truncating it. The file must exist.

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?

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

In a nested structure, how do you access the innermost member? struct outer { struct inner { int value; } in; } obj;

The correct answer is B: obj.in.value. For nested structures accessed through an object, use the dot operator multiple times: obj.in.value accesses the value member of the inner structure.

Which statement is true about void pointers?

The correct answer is A: Cannot be dereferenced without casting. void pointers are generic pointers that must be cast to appropriate type before dereferencing.

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

The correct answer is A: Account for struct padding and alignment differences. 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.

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C Programming

C language from basics to advanced placement prep

291 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 71–80 of 291

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.71 Easy File Handling

What does the fclose() function do?

A Clears the file content

B Closes the file and flushes the buffer

C Moves file pointer to end

D Deletes the file from disk

Correct Answer: B. Closes the file and flushes the buffer

EXPLANATION

fclose() terminates the file stream, flushes any buffered data to disk, and releases the file handle. It doesn't delete or clear the file.

Test

Q.72 Easy File Handling

Which mode allows both reading and writing to a file, creating it if it doesn't exist?

A "r+"

B "w+"

C "a+"

D "rw"

Correct Answer: B. "w+"

EXPLANATION

"w+" opens file for reading and writing, truncating it if it exists, and creating it if it doesn't. "r+" requires file to exist. "a+" opens in append mode with read capability.

Test

Q.73 Easy File Handling

What is the correct syntax to open a file named 'data.txt' in read mode?

A fopen('data.txt', 'r')

B fopen("data.txt", "r")

C open("data.txt", READ)

D file_open("data.txt", 'r')

Correct Answer: B. fopen("data.txt", "r")

EXPLANATION

fopen() uses double quotes for string arguments in C. The first argument is filename and second is mode. Single quotes are for characters, not strings.

Test

Q.74 Easy File Handling

Which function is used to determine the current position in a file?

A ftell()

B fseek()

C rewind()

D fgetpos()

Correct Answer: A. ftell()

EXPLANATION

ftell() returns the current position (as a long integer) of the file pointer in the file. fseek() is used to change position, rewind() resets to beginning, and fgetpos() stores position in a structure.

Test

Q.75 Easy File Handling

In file handling, what does the 'b' flag in file modes like 'rb' or 'wb' indicate?

A Binary mode operation

B Buffered mode operation

C Bidirectional mode operation

D Backup mode operation

Correct Answer: A. Binary mode operation

EXPLANATION

The 'b' flag specifies binary mode, which prevents any translation of line endings or special characters.

Test

Q.76 Easy File Handling

Which of the following file modes in fopen() allows reading only?

A "w"

B "r"

C "a"

D "w+"

Correct Answer: B. "r"

EXPLANATION

The 'r' mode opens a file for reading only. The file must exist, otherwise fopen() returns NULL.

Test

Q.77 Easy File Handling

When opening a file in 'w' mode, what happens if the file already exists?

A The file is truncated and all previous content is deleted

B The file is opened in append mode automatically

C An error is returned and file is not opened

D The file pointer is positioned at the end

Correct Answer: A. The file is truncated and all previous content is deleted

EXPLANATION

Opening a file in 'w' mode truncates the file to zero length if it exists, discarding all previous content.

Test

Q.78 Easy File Handling

Which mode opens a file for writing and truncates it if it exists?

A "w"

B "a"

C "r+"

D "w+"

Correct Answer: A. "w"

EXPLANATION

"w" mode opens a file for writing. If the file exists, it truncates the file to zero length. If it doesn't exist, a new file is created.

Test

Q.79 Easy File Handling

Which function is used to close a file in C?

A fclose()

B close_file()

C file_close()

D closefile()

Correct Answer: A. fclose()

EXPLANATION

fclose() is the standard function to close an opened file stream. It returns 0 on success and EOF on error.

Test

Q.80 Easy File Handling

What does the mode 'rb' mean in fopen()?

A Read in binary mode

B Read and backup mode

C Rewrite and binary mode

D Remove and backup mode

Correct Answer: A. Read in binary mode

EXPLANATION

'rb' mode opens a file for reading in binary format. Binary mode reads the exact bytes without any text conversion.

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