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Last Updated: Mar 27, 2024
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How does #include <bits/stdc++.h> work in C++?

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Prerita Agarwal
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23 Jul, 2024 @ 01:30 PM

Introduction

Hey, Ninjas! In some codes, you may have used more than one include statement and might have been stuck at which one to use for a particular task, and your friend or your teacher came to the rescue and asked you to use include bits/stdc++.h in your code. Most of us used this include statement in our code and didn’t know much about it. Today we will study the working, need, advantages, and disadvantages of include bits/stdc++.h in this article.

how does #include<bits/stdc++.h> work

Let’s begin by learning what is include bits/stdc++.h.

Also, see Literals in C.Fibonacci Series in C++
 

include <bits/stdc++.h>

The include bits/stdc++.h is a header file that we use in our code to include all the standard libraries. It is quite helpful in programming contests and situations where you want to save the time of including different header files. Using the minimum includes is a good idea from the programmer’s perspective. 

include <bits/stdc++.h>

Every advantage comes with a disadvantage, and in this case, the disadvantage is the increased compilation time. Since many unnecessary files are included with this statement, it increases the running time. It increases both the program size and the compile time.

Now, we must know why and when we should use this include statement. You can also do a free certification of Basics of C++.
 

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Why do We Use This Include Statement?

The include bits/stdc++.h is the precompiled header’s implementation file. It includes the standard libraries which are required in our code. It is an excellent idea to minimize the include statement by using this statement. It saves time when speed is an issue, like programming contests. It must be used with the caution as it increases the size of the program and the compile time. It can be helpful in contests but, at the same time, can affect the running time.

use

Let’s understand the advantages and disadvantages in detail.

Also read,Abstract Data Types in C++

Advantages

The following are the advantages of using the include bits/stdc++.h in our code:

✅ It reduces the time wastage of including so many header files, so it is a brilliant idea to use it in programming contests where rank depends on the time.

✅ This statement eliminates the need to write the specific header files for the code; instead, it links all the files simultaneously.

✅ It minimizes the include statements, which shortens the code and increases readability and understandability.

✅ Choosing and remembering the STL file for every function in C++ you use is a bit cumbersome. With this header file, we don’t need to remember the same.

Disadvantages

The include bits/stdc++.h comes with certain disadvantages, let’s discuss them one by one.

❌ This header file includes a lot of useless stuff and thus increases the program size and the compilation time for our code.

❌ The header bits/stdc+.h is a non-standard header file of the GNU C++ library, so using it with another compiler might fail. For example, MSVC ( Microsoft Visual C++ ) does not have this header.

❌ This header is not portable as it is not a part of the C++ standard, and therefore we should avoid it.

❌ Each time the compiler imports the headers from this header file, it recursively searches the file for the compilation of the code.

❌ Along with the issue of bad performance, it is also a bad practice to use this as some programmers just remember this and skip the other header files.

How to Use It?

Since we have learned about the include bits/stdc++.h and have seen all its advantages and disadvantages, we can now decide where we should use it. The next question comes about how we can use it in our C++ code. We can include this header file by simply starting our code with the statement #include <bits/stdc++.h>. Once included this header file, we don’t need to include any specific header file for any function or data structure.

For those who are new to this, let’s understand with an example.

Example

#include <bits/stdc++.h>

using namespace std;

int main(){
    vector<int> v = {5,3,1,4,9,7};

    cout<<endl<<"We can create vector without including standard vector file, as it is included through bits/stdc++.h"<<endl;

    for(auto i:v){
        cout<<i<<" ";
    }
    cout<<endl;

    cout<<"We can use sort function which is included in algorithms header"<<endl;

    sort(v.begin(), v.end());

    cout<<"After Sorting: "<<endl;

    for(auto i:v){
        cout<<i<<" ";
    }
    cout<<endl;

    return 0;
}

Output

Output

You can try and compile with the help of online c++ compiler.

How Compilation is Affected?

The header file include bits/stdc++.h takes more compile time and memory as compared to specific header files because many unnecessary files are also compiled with this.

We can see the difference by replacing the header file ‘include bits/stdc++.h’ with the specific header files.

#include <iostream>
#include<vector>
#include<algorithm>

 

The program which uses the specific headers takes less time and memory, as shown in the below output.

comparison

You can view these details using the following command.

Windows

Run this command in the terminal if you are using Windows.

g++ -ftime-report hello.cpp -o hello.exe

Unix

Run the following command in the Unix operating system.

time g++ hello.cpp -o hello

 

Also, check out this article - Pair in C++

Frequently Asked Questions

What are the uses of C++ language?

C++ language is a general-purpose coding language. It is primarily used for developing operating systems, browsers, applications, and in-game programming. It is an object-oriented language; therefore, it focuses on objects much faster than other languages. 

What are header files?

The headers files are the predefined libraries that include the functions to make coding easier. It contains a huge set of standard library functions and can be included in our program with #include. For example: include bits/stdc++.h.

Is the use of include bits/stdc++.h a good practice?

No, the use of include bits/stdc++.h is not at all a good practice. Most programmers relied only on this header file and forgot the need to learn other header files to be used specifically for the functions. They are usually stuck in a situation where they can’t use this header.

Is “bits/stdc++.h” a standard header?

The header file bits/stdc++.h is not a standard header file of the GNU C++ library; if we try to use it in other compilers, it might fail. Hence it is also not a portable header, and therefore we should avoid using it. For example, MSVC ( Microsoft Visual C++ ) does not support this header. So using include bits/stdc++.h gives an error.

Conclusion

This article was about the C++ language and the include statements. The article discussed the statement include bits/stdc++.h, its use, advantages, and disadvantages. An example of the same is also given at the end. Your concepts must have cleared now, and you must have figured out when and how to use this statement.

You can check out our other articles if you want to dive deep into other concepts related to C++ language -

You can refer to our guided paths on the Coding Ninjas Studio platform to learn more about DSADBMSCompetitive ProgrammingPythonJavaJavaScript, etc. To practice and improve yourself in the interview, you can also check out Top 100 SQL problemsInterview experienceCoding interview questionsand the Ultimate guide path for interviews. Do upvote our blogs to help other ninjas grow.

Happy Coding !!

Topics covered
1.
Introduction
2.
include <bits/stdc++.h>
3.
Why do We Use This Include Statement?
4.
Advantages
5.
Disadvantages
6.
How to Use It?
6.1.
Example
6.2.
Output
7.
How Compilation is Affected?
7.1.
Windows
7.2.
Unix
8.
Frequently Asked Questions
8.1.
What are the uses of C++ language?
8.2.
What are header files?
8.3.
Is the use of include bits/stdc++.h a good practice?
8.4.
Is “bits/stdc++.h” a standard header?
9.
Conclusion