File Handling MCQs – Part 1

Correct Answer: fopen()

Explanation: The `fopen()` function is used to open a file in C. It requires two parameters: the name of the file and the mode in which to open the file (e.g., “r” for reading, “w” for writing).

Correct Answer: fclose(file)

Explanation: The `fclose()` function is used to close an opened file in C. It takes a file pointer as its argument and ensures that all data is flushed and resources are released.

Correct Answer: “rb”

Explanation: The mode “rb” is used to open a file for reading in binary mode. This mode ensures that the file is read as a binary file, and no translation of data occurs.

Correct Answer: Reads formatted input from a file

Explanation: The `fscanf()` function reads formatted input from a file. It works similarly to `scanf()` but takes a file pointer as an additional argument.

Correct Answer: fputc(char, file)

Explanation: The `fputc()` function is used to write a single character to a file. It takes two arguments: the character to be written and the file pointer.

Correct Answer: fseek()

Explanation: The `fseek()` function is used to move the file pointer to a specific position in a file. It allows you to specify an offset and a position from where to begin the offset.

Correct Answer: EOF

Explanation: The `fgetc()` function returns EOF (End of File) when it reaches the end of a file. EOF is a constant defined in the stdio.h header file.

Correct Answer: fputs()

Explanation: The `fputs()` function is used to write a string to a file. It takes two arguments: the string to be written and the file pointer.

Correct Answer: fopen(filename, “a”)

Explanation: The mode “a” in `fopen()` is used to open a file in append mode. This allows you to add data to the end of an existing file without overwriting its content.

Correct Answer: feof()

Explanation: The `feof()` function is used to check for the end-of-file condition in C. It returns a non-zero value if the end of the file has been reached.

Correct Answer: NULL is returned

Explanation: When you attempt to open a non-existent file for reading using `fopen()` with the mode “r” or “rb”, the function returns NULL. This indicates that the file could not be opened, typically because it does not exist or the program does not have read permissions for the file. It is important to always check if `fopen()` returns NULL to handle such cases gracefully.

Correct Answer: fflush(file)

Explanation: The `fflush()` function is used to flush the output buffer of a stream. When writing data to a file, it is often buffered for efficiency. Calling `fflush(file)` ensures that any data still in the buffer is written to the file immediately. This is particularly important for ensuring data integrity, especially if the program might crash or if you need the data to be available for reading immediately.

Correct Answer: Opens a file for reading and writing, and truncates the file to zero length

Explanation: The mode “w+” in `fopen()` opens a file for both reading and writing. If the file already exists, its contents are truncated (i.e., cleared), and the file length is set to zero. If the file does not exist, a new file is created. This mode is useful when you need to both read from and write to a file, starting from an empty state.

Correct Answer: To keep track of the current position within the file

Explanation: In C, a file pointer is used to keep track of the current position within the file. It is a pointer to a FILE structure, which contains information about the file’s state, including the current position, the end-of-file status, and error flags. Using the file pointer, functions like `fgetc()`, `fputc()`, `fread()`, and `fwrite()` can read from or write to specific locations in the file.

Correct Answer: Closes a file and opens another file in the same stream

Explanation: The `freopen()` function is used to close an existing file and open a new file using the same file pointer. It takes three arguments: the name of the new file, the mode in which to open the new file, and the file pointer to be reused. This function is useful when you need to redirect input/output streams, such as redirecting standard input or output to a file.

Correct Answer: By checking if the file pointer is NULL

Explanation: To check if a file was successfully opened using `fopen()`, you should verify if the file pointer returned is NULL. If `fopen()` fails to open the file (due to reasons such as the file not existing, lack of permissions, or other errors), it returns NULL. Therefore, it is a good practice to always check the file pointer for NULL before performing any file operations.

Correct Answer: Opens a file for reading and writing, and appends data to the end

Explanation: The mode “a+” in `fopen()` opens a file for both reading and writing. If the file exists, data is appended to the end of the file. If the file does not exist, a new file is created. This mode allows you to read existing data in the file and add new data without modifying the existing content.

Correct Answer: Reports if an error has occurred on a file stream

Explanation: The `ferror()` function is used to check if an error has occurred on a file stream. It returns a non-zero value if an error has been detected during file operations. This function helps in error handling by allowing the program to detect and respond to file operation errors, such as read or write failures.

Correct Answer: Returns the current position of the file pointer

Explanation: The `ftell()` function returns the current position of the file pointer in a file. This position is given as a long integer representing the number of bytes from the beginning of the file. It is useful for determining where you are in the file, especially when working with large files or when you need to save and restore file positions.

Correct Answer: All of the above

Explanation: It is crucial to close a file using `fclose()` after performing file operations for several reasons. Firstly, it ensures that all buffered data is written to the file, preventing data loss. Secondly, it frees up memory and other resources allocated for the file pointer. Lastly, it helps prevent data corruption and resource leaks, which can occur if files are left open, especially in long-running programs or those that open many files.

Correct Answer: Opens a file for both reading and writing without truncating the file

Explanation: The mode “r+” in `fopen()` is used to open an existing file for both reading and writing without truncating the file. This mode allows you to read the current contents of the file and write new data to it. If the file does not exist, `fopen()` with “r+” mode will return NULL.

Correct Answer: Both B and C

Explanation: The `rewind()` function in C sets the file pointer to the beginning of the file. Additionally, it clears the error and end-of-file indicators for the file stream, effectively resetting the state of the file pointer as if the file had just been opened.

Correct Answer: ftell()

Explanation: The `ftell()` function returns the current position of the file pointer in the file. This value represents the number of bytes from the beginning of the file. It is useful for determining your current location in the file, especially if you need to save and restore this position later.

Correct Answer: “w” creates a new file and writes from the beginning, “a” appends to an existing file

Explanation: The mode “w” in `fopen()` opens a file for writing, creating a new file if it does not exist, and truncating it to zero length if it does exist. The mode “a”, on the other hand, opens a file for writing and appends data to the end of the file without truncating it. If the file does not exist, “a” mode also creates a new file.

Correct Answer: Sets the buffer size for file I/O operations

Explanation: The `setvbuf()` function in C sets the buffer size for file I/O operations. It allows you to specify a buffer, the mode of buffering (fully buffered, line buffered, or unbuffered), and the size of the buffer. This function can help optimize file I/O performance by controlling how data is buffered during read and write operations.

Correct Answer: fopen(filename, “rb+”)

Explanation: The mode “rb+” in `fopen()` opens a file for both reading and writing in binary mode without truncating it. This mode is useful when you need to read and modify binary files while preserving their existing content. If the file does not exist, `fopen()` with “rb+” mode will return NULL.

Correct Answer: The program continues with no effect

Explanation: Using `fclose()` on a NULL file pointer has no effect and the program continues to run. The function checks if the file pointer is NULL and if so, it does nothing. This can be useful in situations where a file pointer might be NULL due to a failed `fopen()` call, and you want to ensure `fclose()` is called safely.

Correct Answer: “a+”

Explanation: The mode “a+” in `fopen()` opens a file for both reading and writing. If the file exists, it appends new data to the end of the file without truncating it. If the file does not exist, a new file is created. This mode allows you to read from an existing file and add new data at the end.

Correct Answer: Returns a NULL pointer

Explanation: When `fopen()` fails to open a file, it returns a NULL pointer. This typically happens if the file does not exist (when opening in read mode), if there are insufficient permissions, or if there is another error related to file handling. Checking for a NULL pointer after calling `fopen()` is essential for robust error handling in file operations.

Correct Answer: To write a binary file, truncating it if it exists

Explanation: The mode “wb” in `fopen()` is used to write to a binary file. If the file already exists, it is truncated to zero length, effectively clearing its contents. If the file does not exist, a new file is created. This mode is appropriate when you need to create or overwrite a binary file, ensuring that any previous content is removed.

Correct Answer: fgetc()

Explanation: The `fgetc()` function is used to read a single character from a file in C. It returns the character read as an unsigned char cast to an int or EOF on end-of-file or error.

Correct Answer: `getc()` and `fgetc()` are identical

Explanation: In standard C, `getc()` and `fgetc()` are interchangeable and both are used to read a single character from a file. They return the character read as an unsigned char cast to an int or EOF on end-of-file or error.

Correct Answer: fwrite()

Explanation: The `fwrite()` function is used to write a block of data to a file in C. It takes four arguments: a pointer to the data to be written, the size of each element to write, the number of elements to write, and the file pointer.

Correct Answer: `feof()` returns a non-zero value

Explanation: The `feof()` function returns a non-zero value if the end-of-file indicator for the file stream has been set, indicating that there are no more characters to read from the file.

Correct Answer: Reads a line of text from a file

Explanation: The `fgets()` function is used to read a line of text from a file, including the newline character. It takes three arguments: a buffer to store the read string, the maximum number of characters to read, and the file pointer.

Correct Answer: fread()

Explanation: The `fread()` function is used to read binary data from a file in C. It takes four arguments: a pointer to the buffer where data is read into, the size of each element to read, the number of elements to read, and the file pointer.

Correct Answer: Use a loop with `fgets()` and check for EOF

Explanation: To read an entire file line by line using `fgets()` in C, you typically use a loop that calls `fgets()` inside it. Each call reads one line of text until `fgets()` returns NULL (indicating end-of-file or error). This method ensures that you can process each line of the file individually.

Correct Answer: Writes formatted output to a file

Explanation: The `fprintf()` function in C is used to write formatted output to a file. It works similarly to `printf()`, but instead of printing to the console, it writes formatted data to a specified file stream. It takes a format string and additional arguments to generate formatted output.

Correct Answer: `fprintf(file, “%s”, str);`

Explanation: To write a string `str` to a file using `fprintf()` in C, you use the format specifier `%s` in the format string along with the file pointer (`file`) and the string (`str`) as arguments. This function allows you to write formatted strings and other data types to a file.

Correct Answer: Size of each element to write

Explanation: In the `fwrite()` function in C, the second argument specifies the size of each element to write. Together with the first argument (pointer to data), it determines how much data is written to the file. The total amount of data written is calculated as `number_of_elements * size_of_each_element`.

Correct Answer: Checks if the end-of-file indicator is set for a file stream

Explanation: The `feof()` function in C checks if the end-of-file (EOF) indicator is set for a file stream. It returns a non-zero value if EOF has been reached during a previous read operation on the file stream.

Correct Answer: `fread(buffer, sizeof(buffer), 1, file);`

Explanation: To read binary data from a file using `fread()` in C, you specify the buffer where data will be stored, the size of each element to read (typically `sizeof(buffer)`), the number of elements to read (1 in this case to read one block), and the file pointer (`file`).

Correct Answer: Moves the file pointer to the beginning of the file

Explanation: The `rewind()` function in C moves the file pointer associated with the given file stream to the beginning of the file. It also clears the error and end-of-file indicators for the file stream, allowing subsequent operations to start reading from the beginning.

Correct Answer: By checking if the file pointer is not NULL

Explanation: When you use `fopen()` to open a file for writing in C, the function returns a non-NULL file pointer if the file was opened successfully. Checking if the file pointer is not NULL ensures that the file was indeed opened, allowing you to proceed with writing operations.

Correct Answer: Truncates the file to zero length

Explanation: When you open an existing file in write mode “w” using `fopen()` in C, the file is truncated to zero length. This means that the existing content of the file is erased, and if the file does not exist, a new file is created.

Correct Answer: Opens a file for writing, appending data to the end

Explanation: The mode “a” in `fopen()` opens a file for writing. If the file does not exist, it creates a new file. If the file exists, it appends data to the end of the file without truncating it. This mode is useful when you want to add data to an existing file without overwriting its content.

Correct Answer: `fscanf(file, “%s”, str);`

Explanation: To read a formatted string from a file using `fscanf()` in C, you use the format specifier `%s` in the format string along with the file pointer (`file`) and the buffer (`str`) where the string will be stored. This function reads characters from the file until whitespace is encountered.

Correct Answer: `fputc()`

Explanation: The `fputc()` function is used to write a single character to a file in C. It takes two arguments: the character to be written and the file pointer (`file`) where the character will be written.

Correct Answer: `fprintf(file, “%s”, line);`

Explanation: To write a line of text `line` to a file using `fprintf()` in C, you use the format specifier `%s` in the format string along with the file pointer (`file`) and the string (`line`) that contains the text to be written. This function allows you to write formatted text and other data types to a file.

Correct Answer: `fputc()` and `putc()` are identical

Explanation: In standard C, `fputc()` and `putc()` are interchangeable and both are used to write a single character to a file. They return the character written as an unsigned char cast to an int or EOF on error.

Correct Answer: Beginning of the file

Explanation: When a file is opened in read mode “r” using `fopen()` in C, the initial position of the file pointer is at the beginning of the file. Subsequent read operations will start from this position unless the file pointer is moved using functions like `fseek()`.

Correct Answer: fseek()

Explanation: The `fseek()` function in C is used to move the file pointer associated with a file stream (`FILE *`) to a specific location within the file. It takes three arguments: the file pointer, an offset (number of bytes to move), and a position indicator (such as `SEEK_SET`, `SEEK_CUR`, or `SEEK_END`).

Correct Answer: Current position of the file pointer

Explanation: The `ftell()` function in C returns the current position of the file pointer associated with the file stream. This position is represented as a long integer, indicating the number of bytes from the beginning of the file to the current position.

Correct Answer: “r+”

Explanation: The mode “r+” in `fopen()` allows you to open a file for both reading and writing without truncating it. It preserves the existing content of the file and allows you to read from and write to any part of the file.

Correct Answer: 1

Explanation: The `feof()` function in C returns a non-zero value (typically 1) after it has encountered the end-of-file (EOF) condition during a read operation on the file stream. This can be used to check if all data has been read from the file.

Correct Answer: Moves the file pointer to a specified position

Explanation: The `fseek()` function in C is used to move the file pointer associated with a file stream to a specified position within the file. It allows random access to different parts of the file based on the offset and position indicator provided.

Correct Answer: rewind(file)

Explanation: The `rewind()` function in C is used to reposition the file pointer associated with a file stream (`FILE *`) to the beginning of the file. It is equivalent to calling `fseek(file, 0, SEEK_SET)` but is more straightforward for resetting the file pointer to the start of the file.

Correct Answer: Returns 0

Explanation: If you use `ftell()` immediately after opening a file in “w” mode using `fopen()` in C, it typically returns 0. This is because the file is initially empty (truncated to zero length), so the current position of the file pointer is at the beginning of the file.

Correct Answer: Saves the current position of the file pointer

Explanation: The `fgetpos()` function in C saves the current position of the file pointer associated with a file stream (`FILE *`). It stores this position in an object of type `fpos_t`, allowing you to later restore the file pointer to the same position using `fsetpos()`.

Correct Answer: fsetpos()

Explanation: The `fsetpos()` function in C is used to set the file pointer associated with a file stream (`FILE *`) to a previously saved position. It takes two arguments: the file pointer and a pointer to an object of type `fpos_t`, which contains the saved position obtained from `fgetpos()`.

Correct Answer: fclose()

Explanation: The `fclose()` function in C is used to close a file stream that was previously opened using `fopen()`. It flushes any buffered data to the file and releases any resources associated with the file stream.

Correct Answer: Causes an error

Explanation: Using `fseek()` on a file opened in “r” mode (read-only mode) causes an error. The “r” mode restricts operations that modify the file, including positioning the file pointer using `fseek()`. Instead, you should use `ftell()` to determine the current position or `rewind()` to move the pointer to the beginning of the file.

Correct Answer: Flushes output buffer

Explanation: The `fflush()` function in C is used to flush (clear) the output buffer associated with a file stream. This ensures that any data written using functions like `fprintf()` or `fwrite()` is actually written to the file immediately, rather than being held in the buffer.

Correct Answer: getc()

Explanation: The `getc()` function in C reads a single character from the file stream and advances the file pointer. It returns the character read as an unsigned char cast to an int or EOF if end-of-file or error occurs.

Correct Answer: int

Explanation: The `fseek()` function in C returns an integer value that indicates whether the operation was successful. It returns 0 on success and non-zero value (typically -1) on failure.

Correct Answer: `fseek(file, 0, SEEK_END);`

Explanation: To move the file pointer to the end of a file using `fseek()` in C, you use the position indicator `SEEK_END` along with an offset of 0. This sets the file pointer to the end of the file, allowing you to append data or determine the file size using `ftell()`.

Correct Answer: ferror()

Explanation: The `ferror()` function in C is used to check if a file operation encountered an error. It returns a non-zero value if an error occurred on the file stream, indicating that subsequent operations on the file may fail.

Correct Answer: 1

Explanation: The `feof()` function in C returns a non-zero value (typically 1) if the end-of-file (EOF) indicator is set for the file stream. This indicates that all data has been read from the file and further read operations will return EOF.

Correct Answer: Opens a file for reading in binary mode

Explanation: The mode “rb” in `fopen()` opens a file for reading in binary mode in C. This mode is used when dealing with binary data that may include characters not representable in text mode, such as images or executable files.

Correct Answer: `fseek(file, offset, SEEK_SET);`

Explanation: To move the file pointer to a specific byte offset from the beginning of the file using `fseek()` in C, you use the position indicator `SEEK_SET` along with the desired offset in bytes (`offset`). This allows random access to different parts of the file based on the specified position.

Correct Answer: They can store any type of data, including images and executables

Explanation: Binary files in C can store data in any format, including images, executables, and other non-textual data. They are not restricted to storing only human-readable text characters.

Correct Answer: fgets()

Explanation: The `fgets()` function in C is typically used to read from a text file. It reads a line of text from the file stream, including the newline character, and stores it into a buffer.

Correct Answer: It reads characters in binary format

Explanation: `fread()` in C reads a specified number of elements (each of a specified size in bytes) from a file stream into a buffer. It does not distinguish between text and binary data; it reads characters in their binary representation.

Correct Answer: “rb”

Explanation: The mode “rb” in `fopen()` is used to open a file for reading and writing binary data in C. This mode ensures that the file is treated as a binary file, allowing you to read and write binary data using functions like `fread()` and `fwrite()`.

Correct Answer: They cannot store newline characters

Explanation: Text files in C store data as human-readable text characters. They can contain newline characters (`’\n’`) and are typically smaller in size compared to binary files due to the textual representation of data.

Correct Answer: Ability to store any type of data

Explanation: Binary files in C can store data in any format, including non-textual data such as images and executables. This flexibility allows binary files to be used for a wide range of applications where data types vary.

Correct Answer: fprintf()

Explanation: The `fprintf()` function in C is used to write formatted data to a text file. It takes a format string and additional arguments corresponding to the format specifiers in the string, allowing you to write data in a specified format.

Correct Answer: 0

Explanation: `fread()` in C returns the number of elements successfully read. If an error occurs during reading, it returns 0, indicating that no elements were read.

Correct Answer: “r”

Explanation: If no mode is specified when opening a file using `fopen()` in C, the default mode is “r” (read mode). This allows you to open an existing file for reading.

Correct Answer: Opens a file for writing in binary mode, truncating it to zero length

Explanation: The mode “wb” in `fopen()` opens a file for writing in binary mode in C. If the file exists, it truncates the file to zero length, erasing its previous content. If the file does not exist, it creates a new empty file for writing binary data.

Correct Answer: fputc()

Explanation: The `fputc()` function in C is used to write a single character to a text file. It takes two arguments: the character to be written and the file pointer (`FILE *`) where the character will be written.

Correct Answer: Opens the file for reading binary data

Explanation: Opening a text file in “rb” mode using `fopen()` in C opens the file for reading binary data. This mode allows reading of binary data from a file that is treated as a text file, but without any translation of newline characters.

Correct Answer: fwrite()

Explanation: The `fwrite()` function in C is used to write a block of data to a file. It takes four arguments: a pointer to the data to be written, the size of each element in bytes, the number of elements to write, and the file pointer (`FILE *`) where the data will be written.

Correct Answer: “r”

Explanation: If no mode is specified when opening a file using `fopen()` in C, the default mode is “r” (read mode). This allows you to open an existing file for reading.

Correct Answer: EOF

Explanation: The `fgetc()` function in C returns EOF (End-Of-File) if it encounters the end-of-file condition while reading from a file stream. This typically happens when there are no more characters to read from the file.

Correct Answer: fgetc()

Explanation: The `fgetc()` function in C is used to read a single character from a text file. It returns the character read as an unsigned char cast to an int or EOF if end-of-file or error occurs.

Correct Answer: “a”

Explanation: The mode “a” in `fopen()` opens a file for writing data to the end of the file (“append mode”) in C. If the file does not exist, it creates a new file. If the file exists, data is appended to its end without truncating existing content.

Correct Answer: fgets()

Explanation: The `fgets()` function in C is used to read a line of text from a text file. It reads characters from the file stream until a newline character (`’\n’`) or end-of-file is encountered, and stores them in a buffer.

Correct Answer: “rb” mode opens a file in binary mode, “r” mode opens in text mode

Explanation: In `fopen()` in C, “rb” mode opens a file in binary mode, which means the file is treated as a binary file and no newline translations are performed. “r” mode opens a file in text mode, where newline translations may occur.

Correct Answer: Writes a character to a file

Explanation: The `putc()` function in C writes a single character to a file. It takes two arguments: the character to be written and the file pointer (`FILE *`) where the character will be written.

Correct Answer: ferror()

Explanation: The `ferror()` function in C is used to check if a file operation encountered an error. It returns a non-zero value if an error occurred on the file stream, indicating that subsequent operations on the file may fail.

Correct Answer: Prints the last encountered error message

Explanation: The `perror()` function in C prints an error message corresponding to the last encountered error. It typically prints the message to stderr, describing the error condition that occurred during a file or stream operation.

Correct Answer: clearerr()

Explanation: The `clearerr()` function in C is used to clear the error and end-of-file indicators for a given file stream (`FILE *`). It resets both indicators so that subsequent operations on the file stream can be performed without the influence of previous error conditions.

Correct Answer: 0

Explanation: `ferror()` in C returns 0 if no error has occurred on the file stream. This indicates that the last file operation on the stream was successful without encountering any errors.

Correct Answer: EOF

Explanation: The `EOF` macro in C is used to indicate the end-of-file condition when reading from a file stream. It is returned by functions like `getc()` and `fgetc()` when the end of the file is reached.

Correct Answer: Returns 0

Explanation: If you use `feof()` immediately after opening a file in “w” mode using `fopen()` in C, it typically returns 0. This is because the file is initially empty (truncated to zero length), and the end-of-file indicator is not set until data is written and read from the file.

Correct Answer: When encountering an error during a file operation

Explanation: The `perror()` function in C prints an error message when encountering an error during a file or stream operation. It is typically used after a function like `fopen()`, `fclose()`, `fread()`, or `fwrite()` returns an error indicator.

Correct Answer: strerror()

Explanation: The `strerror()` function in C can be used to retrieve a string describing the last error encountered during a file operation. It takes an error code as input and returns a pointer to a string containing the error message.

Correct Answer: Clears the error and end-of-file indicators

Explanation: The `clearerr()` function in C clears the error and end-of-file indicators for a given file stream (`FILE *`). It resets both indicators so that subsequent operations on the file stream can be performed without the influence of previous error conditions.

Correct Answer: feof()

Explanation: The `feof()` function in C is used to check if the end-of-file (EOF) indicator is set on a file stream. It returns a non-zero value (typically 1) if the EOF indicator is set, indicating that all data has been read from the file.