C++ <cstdio>

The <cstdio> header file is a part of the C++ standard library collection that provides the input and output methods of <stdio.h> library of C language. We can use the traditional C-style input and output method in C++ using the <cstdio> library. It also contains all the functions and macros of <stdio.h> library of C language. 

We can import <cstdio> library using #include preprocessor directive in our program.

Syntax:

#include <cstdio>

Example:

// C++ program to demonstrate the use of <cstdio> header
// file
#include <cstdio>

using namespace std;

int main()
{
    int number = 10;

    // using printf() function of C language in C++
    printf("Value of variable \"number\": %d", number);

    return 0;
}

Value of variable "number": 10

<cstdio> Library Functions

Input and output in C++ are done in the form of a sequence of bytes commonly known as streams. The stream can be of many types depending on where the data is being sent or received. For example,

• Standard Input Stream(stdin): The flow of data in this stream is from the standard input device(keyboard) to the memory.
• Standard Output Stream(stdout): The flow of data in this stream is from memory to the standard output device (monitor).
• File Stream: The flow of data is to or from the specified file.

<cstdio> library functions help us to manipulate these streams according to our needs. Following are all those functions with the streams that they manipulate.

Input and Output Functions

Input and output are done in <cstdio> by the printf() and scanf() functions and its variations.

File Operation Functions

Sometimes, we need to store output data or take input from an external file. In these cases we can use the following functions of <cstdio> library for doing operations on file:

To know more about file-handling operations, click here.

Example:

// C++ program to demonstrate use of cstdio functions
#include <cstdio>

using namespace std;

int main()
{
    // using printf()
    printf("This is printf() function\n");
    // using fprintf() to print output in standard output
    // device using stdin pointer
    fprintf(stdout, "This is fprintf() function");

    return 0;
}

This is printf() function
This is fprintf() function

Macros of <cstdio> library

Macros are the constants that are defined by the #define preprocessor directive. They are replaced by their values during preprocessing. To know more about macros, click here.

Below is the list of frequently used functions of <cstdio> library:

Example:

// C++ program to print values of some constant macros
#include <cstdio>

using namespace std;

int main()
{
    printf("Value of NULL: %d\n", NULL);

    printf("Value of EOF: %d\n", EOF);

    return 0;
}

Value of NULL: 0
Value of EOF: -1

Note: Value of NULL and EOF are implementation defined and depends on the compiler vendor.

Difference between cstdio and iostream libraries

As we know that <iostream> header file contains the standard input and output methods of C++. So here is the list of major differences between <cstdio> and <iostream>