User-defined header files in C++

The ISO standard for the language does not include user-header files. Generally speaking, they are all the header files the programmers have defined for things like holding unique library functions. The user installs them manually, or a particular vendor may have included them in the compiler. For their convenience, the programmer defines them.

Here are a few C++ user-standard header files:

<bits/stdc++.h>

All of the header files' standard libraries are included in it. You won't need to include any additional standard header files if you include them in your code. However, since it is a non-standard header file from the GNU C++ library, compiling your code with a compiler other than GCC may not work; for example, MSVC may not contain this header.

It is essentially a header file with all of the standard libraries. If you want to reduce your time on chores during programming contests, using this file is a good idea, mainly when your rank is time-sensitive.

People emphasize finding the algorithm to solve problems more than software engineering when battling in programming competitions. From the software engineering perspective, minimizing the include makes sense. If you use it, it comes with many files that your program might not need, which adds unnecessary size and compile time to your program.

Example:

For instance, we do not need to write the <cmath> header file in the code to use the pow() function found in the <bits/stdc++.h> header file. However, to run the pow() function when using the <iostream> header file, we also need to write the <cmath> header file; otherwise, the compiler will report that 'pow' was not declared in this scope.

#include <bits/stdc++.h>

using namespace std;

int main() {

    double value = 58.0;

    double outcome = pow(value, 2.4);

    cout << outcome;

    return 0;

}

Output:

Benefits of Standard C++/Bits

• Not every GNU C++ function requires you to know every bit of STL.
• This also reduces the work needed to write all the necessary header files.
• If you want to reduce your time on tasks during contests—especially if your rank is time-sensitive—you should consider using this file.

The drawbacks of using bits/stdc++

• Please avoid using this header file as it is not portable and is not included in the C++ standard.
• Bits/stdc++.h is a user-defined header file in the GNU C++ library. For example, MSVC may not have this header, so trying to compile your code with a compiler other than GCC may not work.
• Furthermore, even if specific headers were included in the standard, you would want to prevent utilizing catch-all headers instead because the compiler has to read in and parse every comprised header—including repeatedly comprised headers—every time that translation unit is compiled.
• Using it would result in a longer compilation time and much unnecessary content.

<Qpushbutton>

It has a push button component from the C++ Qt GUI Library.

Make your own C and C++ header files.

Rather than composing voluminous and intricate code, we can generate our header files and incorporate them into our application for convenience. The readability and functionality of the code are improved. The procedures to make our header file are listed below:

1. Make a file ending in ".h" and compose your C/C++ code.

int multiplyThreeNumbers(int x, int y, int z)

{

return (x*y*z);

}

2. As demonstrated below, add "#include" to your header file in your C/C++ program.

#include "iostream"

#include "multiply.h"

using namespace std;

int main()

{

          int x = 8, y = 5, z = 3;

          cout << "The product of three numbers is: " << multiplyThreeNumbers(x, y, z) ;

}

Output

In C++, user-defined header files have various significant functions in software development:

Add guards to the header files (using #ifndef, #define, and #endif) to prevent a translation unit from containing the same header file more than once

You can declare a module's interface (function prototypes, class declarations, constants, etc.) in header files without disclosing how it is implemented. This encourages encapsulation because the implementation specifics can be maintained in different source files.

To utilize a module's functionality, users only need to include the header file; they are not required to understand the inner workings of the functions or classes.