What is File handling in C++?

• File handling in C++ refers to the ability of a C++ program to read data and write data to files.
• File handling allows programs to interact with external files, such as text files, binary files, and more.

C++ Streams

• istream: Used for input (e.g., cin for keyboard input).
• ostream: Used for output (e.g., cout for console output).

C++ Predefined Streams

• cin: Standard input stream, used for reading from the keyboard.
• cout: Standard output stream, used for writing to the console.
• cerr: Standard error stream, used for writing error messages to the console.

I/O Operations

Unformatted Console I/O Operations

Manipulators

• Manipulators are functions or objects that allow you to control the formatting of data when it's being displayed.
• For example, std::setw() sets the width of the output field, ensuring that the output is neatly aligned.

File Modes in C++

Input Mode (ios::in)

• When you open a file with ios::in mode, you are specifying that you intend to read data from the file.
• If the file does not exist or cannot be opened for reading, an error will occur.

Input Mode in C++ Example

Output Mode (ios::out)

• This mode is used to open a file for writing.
• If the file exists, its content will be truncated; if it doesn't exist, a new file will be created.
• Syntax:

Output Mode in C++

Append Mode (

Append Mode in C++

Binary Mode (

Binary Mode in C++

Opening and Closing a File in C++

• In C++, you can work with files by using ifstream (for reading) and ofstream (for writing) classes.
• To open a file, you typically provide its name and specify the mode (ios::in for input, ios::out for output).

Error Handling during File Operations in C++

• When working with files, it's essential to check whether file operations were successful.
• For example, when opening a file, you should verify if it opened successfully using the is_open() function.

Sequential Access to File

• Sequential access to a file means reading or writing data in the order it appears in the file, from the beginning to the end.
• Here's an example of reading and writing sequentially to a file:

Random Input and Output Operations

• Random input and output operations involve moving the file pointer to a specific location in the file and reading or writing data from that point.
• Here's an example of random access:

• In this code, we open a file for both reading and writing. We use seekp to set the file pointer to position 10 and write "Hello" there.
• Then, we use seekg to move the file pointer to position 5 and read data from that position.

Persistent Objects

• In this code, we have a Person class with Save and Load methods to serialize and deserialize the object's data to/from a file.
• We save a Person object to a file, and then we load and display the saved object.

Command Line Arguments

• Command line arguments are values passed to a program when it is executed from the command line.
• Here's a simple example of how to access and use command line arguments:

• In this code, argc represents the number of command line arguments, and argv is an array of C-style strings (char arrays) containing the actual argument values.
• We print the number of arguments and then loop through and print each argument's value.

Conclusion