Question

is header file must in c programming?

Answer 1

Yes if you want that your code should run efficiently without giving any error then it is required to include header files. For example #include<stdio.h> this header file contains the meaning of the predefined functions like printf() and scanf() in c. unless and untill you are not adding this header file you cannot use the predefined functions in your code.

Answer 2

It is possible to write code not using is header files but using header files is more reliable  than not using.

Answer 3

yes header file is must in c programming

Answer 4

Depends on what you mean.

If you mean needing to link a header file, technically no but you probably wouldn't. For starters, without any includes you need to be proficient in your systems assembly to log anything into the terminal.

If you mean needing to make your header files, while it is not something you are forced to do, it is a good idea if you are making a somewhat large project where putting everything into one file may not be very practical.

Answer 5

No, it's not. However, they exist for convenience and to help deal with larger projects so code wouldn't need to be copied over and over.

You can include header files provided by others, e.g. <stdio.h> for standard input/output operations, and you can also make your own header files if you want to share types across multiple files or you'd like to offer functionality for 3rd parties (e.g. you're creating an API).

It is highly recommended to create header files for anything more than a single file project.

Update

I've seen some people saying you need stdio.h or other headers. This is not true. They exist for your convenience, but you do not absolutely need to use them. You can just pick the function declarations from those headers that you would actually use in your code. They work because the header file contains just the declarations, but the definitions live somewhere else and they will be linked against your compiled project automatically (at least the standard library functions).

Here's an illustration below. Enjoy!

extern int printf(const char * format, ...);
extern int scanf(const char * format, ...);

int main()
{
    printf("Did you know you do not absoutely need to include stdio.h?\n");
    scanf("%*s");
    printf("Isn't this amazing?!");

    return 0;
}

Answer 6

printf and scanf functions are there in  header files only i you want to use them you have to include header file