File Management in C++
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Questions and Answers

What is the default mode when opening a file for output using ofstream?

  • ios::out (correct)
  • ios::binary
  • ios::app
  • ios::in

    • Which of the following modes will cause a file to be opened in binary mode?

  • ios::ate
  • ios::nocreate
  • ios::trunc
  • ios::binary (correct)

    • What will the ios::trunc mode do if the file already exists?

  • Discard the file's content (correct)
  • Move the read pointer to the end of the file
  • Append data to the existing content
  • Fail to open the file

    • Which of the following modes, when combined with ios::out, ensures that new data is written to the end of the file?

    <p>ios::app</p> Signup and view all the answers

    To open a stream for both input and output, which mode values must be specified?

    <p><code>ios::in</code> and <code>ios::out</code> combined</p> Signup and view all the answers

    What is a 'logical file' in the context of file processing?

    <p>An object in RAM representing a file, pointed to by a file variable.</p> Signup and view all the answers

    Why does C++ use streams for file I/O?

    <p>To provide a consistent interface irrespective of the accessed device.</p> Signup and view all the answers

    What is the key difference between text and binary streams?

    <p>Text streams perform character translations, while binary streams maintain a one-to-one byte correspondence.</p> Signup and view all the answers

    In a text stream, what does a new line character typically convert to?

    <p>A carriage return/linefeed pair.</p> Signup and view all the answers

    For a binary stream, what is the crucial characteristic regarding the number of bytes written or read?

    <p>The number of bytes written or read matches the number on the external device.</p> Signup and view all the answers

    What process establishes a connection between a stream and a specific file?

    <p>An open operation.</p> Signup and view all the answers

    Why might an implementation defined number of null bytes be appended to a binary stream?

    <p>To pad information to fill a sector on the disk.</p> Signup and view all the answers

    Which of the following is NOT considered a file type within the context of C++ file I/O?

    <p>A RAM location</p> Signup and view all the answers

    What is the primary difference between how a text file and a binary file store data?

    <p>Text files store data as a sequence of characters, while binary files store data as a sequence of records in a format related to its data type.</p> Signup and view all the answers

    If an integer with the value 321 is written to a text file and a binary file, how does the storage size differ?

    <p>It will take three bytes in the text file and two bytes in the binary file.</p> Signup and view all the answers

    When you open a binary file and see characters instead of the numeric value that was stored, why does this happen?

    <p>The characters represent the ASCII values of the bytes in the binary data.</p> Signup and view all the answers

    What are the steps involved in file processing?

    <p>Declaring, opening, processing, and closing the file.</p> Signup and view all the answers

    What is a stream object in C++ file processing?

    <p>A stream object is how the physical file gets accessed in C++.</p> Signup and view all the answers

    Which class would you use to declare a stream that only performs input operations from a file?

    <p>ifstream</p> Signup and view all the answers

    What action is performed by the open() method in file processing?

    <p>It associates a stream object with a physical file.</p> Signup and view all the answers

    Which class would you use to declare a stream that performs both input and output operations on a file?

    <p>fstream</p> Signup and view all the answers

    What happens to the file position indicator when a file that supports position requests is opened?

    <p>It is initialized to the start of the file.</p> Signup and view all the answers

    What is the term for the process of writing the contents of a stream to an external device when a file opened for output is closed?

    <p>Flushing</p> Signup and view all the answers

    What data type is used for a file pointer?

    <p>FILE *</p> Signup and view all the answers

    Which header file is essential for performing file I/O operations using classes such as ifstream, ofstream, and fstream?

    <p>fstream.h</p> Signup and view all the answers

    From which class are the C++ file I/O classes ifstream and ofstream directly derived?

    <p>istream and ostream</p> Signup and view all the answers

    Which of the following is NOT one of the standard streams that are automatically opened when a program starts execution?

    <p>stdfin</p> Signup and view all the answers

    If a program terminates normally, what happens to all open files?

    <p>They are automatically closed.</p> Signup and view all the answers

    What is the primary purpose of the file control structure of type FILE?

    <p>To store information such as name, status, and position of the file.</p> Signup and view all the answers

    Study Notes

    File Management in C++

    • File handling is a crucial part of any program.
    • Applications often save and retrieve data from local storage (disk).
    • Physical files reside on secondary storage.
    • Logical files are created in RAM for program processing.
    • Logical files are objects with file data types.
    • A variable, often called a file handler, points to the logical file.
    • C++ file I/O classes simplify file operations (read/write).

    Streams and Files

    • The I/O system provides a consistent interface to programmers, independent of the actual devices being accessed.
    • This abstraction layer is called a stream.
    • The actual device is called a file.
    • C++ can handle various devices (terminals, disk drives, tape drives), treating them as logical streams.
    • Streams are categorized as text or binary.

    Text Streams

    • A text stream is a sequence of characters.
    • Character translations (like newlines converted to carriage return/linefeed pairs) might occur based on the host environment.
    • There might not be a perfect one-to-one correspondence between characters written/read and those on the external device due to transformations.

    Binary Streams

    • A binary stream directly corresponds to bytes on the external device (no character translations).
    • The number of bytes written/read matches the number on the external device.
    • Implementation-defined null bytes might be appended to fill sectors, if needed.

    Files in C++

    • C++ files can be anything from disk files to terminals or printers.
    • A stream is associated with a file through an "open" operation.
    • Information exchange happens between the program and the open file.
    • All streams are similar, but files can vary.
    • If a file allows position requests, opening it initializes the file position indicator to the start of the file.

    File Position Indicator

    • The file position indicator increments after each character read/written.
    • Dissociating a file from a stream uses a "close" operation.
    • Closing an output file involves writing any pending contents (flushing).
    • Files are automatically closed when a program finishes normally; abnormal termination might leave files open.

    File Control Structure

    • Stream-file associations have file control structures (type FILE).
    • stdio.h defines this structure.

    The File Pointer

    • A file pointer points to file information (name, status, current position).
    • It's used by the associated stream to control I/O operations.
    • A file pointer is a variable of type FILE.

    Standard Streams

    • Three streams (stdin, stdout, stderr) open automatically when a program starts.
    • They typically point to the console (for input/output/error).
    • These streams are file pointers, used by ANSI C file system for console I/O operations.

    C++ File I/O Classes and Functions

    • To do file I/O, include the header fstream.h.
    • fstream.h defines classes: ifstream (input), ofstream (output), fstream (both).
    • These classes inherit from istream and ostream, which in turn inherit from ios.

    File Types: Text and Binary

    • Files are often classified as text or binary.
    • Text files store content as a sequence of characters and are read sequentially.
    • Binary files store content in a binary format (directly mapped to memory).

    Opening and Closing Files

    • To open a file, link the file to a stream using the "open" method.
    • Input-only streams are ifstream; output-only are ofstream; both are fstream.
    • The open method needs parameters like file name, mode, and access.
    • Closing the stream disassociates the stream and the file; this action flushes data.

    Modes for Opening Files

    • Modes like ios::app, ios::ate, ios::binary, ios::in, ios::nocreat, ios::noreplace, ios::out, ios::trunc control opening behavior.
    • They determine how the file is opened (append, move to end, binary mode, input, etc.)

    Checking State Flags

    • Member functions like bad(), fail(), eof(), and good() examine stream states (errors, end-of-file).
    • Use them to check success of operations.

    Stream Pointers

    • I/O streams have internal pointers (get pointer and put pointer).
    • The get pointer tracks the next element to read.
    • The put pointer tracks where the next element will be written.

    tellg() and tellp()

    • These functions return the current position of the get pointer or the put pointer.

    seekg() and seekp()

    • You can manipulate the positions of get and put pointers within the stream using seekg() and seekp().

    get(), put(), read(), write()

    • These methods are used for byte-oriented operations (reading/writing bytes).

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    Chapter 3 File Management PDF

    Description

    This quiz focuses on the fundamentals of file management in C++, covering file handling, logical and physical files, and the use of streams. You'll explore how C++ simplifies file operations and the differences between text and binary streams. Test your knowledge of these essential programming concepts!

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