Getting started with C

Whether the full function is there or linked later is a matter of implementation (some headers have full functions, typically trivial "inline" functions).

I can't remember what the standard says via the stdlib, but in general a library you load later on may not have all/some of those functions, but as long as you didn't use them you'll be fine (just as with a redundant forward declaration you yourself did).

And finally the whole "linking" part of C is mostly just a widespread convention, not something that the standard really dictates. See section 6.2.2 [1] for the brief words on it mainly to do with "static"/"extern". But the whole "compile" -> "link" (to some existing .so/.a) -> "program" is all implementation defined.

1. http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

To test my theory, I asked the OpenAI API to complete the following sentence:

    This tutorial will guide you through writing the "Hello World" program in the C programming language.

    This tutorial will guide you through writing the "Hello World" program in the C programming language.
    
    Hello World Program Structure

    The "Hello World" program is a very simple program. It consists of two parts: the main function and the printf function. The main function is the first function called when your program starts running. It is responsible for starting all other functions and initializing everything that needs to be initialized before your program starts doing anything useful. The printf function is responsible for printing text to the screen. In this case, it prints "Hello World!" to the screen.
    
    The main Function
    
    The main function must have one argument which is an integer that represents how many arguments were passed into it from the command line (if any). The following code shows a simple main function:

    #include 
    int main(int argc, char *argv[]) {
        printf("Hello World!n");
        return 0;
    }

    This code will print "Hello World!" to the screen when executed.

    Let's go over each line of this code:

    #include 
    This line tells the compiler to include stdio.h in our program so we can use its functions (like printf ).

    int main(int argc, char *argv[])
    This declares a new variable called main . It has two arguments: argc and argv . These are special variables that are used by C programs to pass information into their functions from their command line arguments (if any). We'll talk more about them later on in this tutorial when we cover how to use command line arguments with your programs. For now, just know that they're there so we can use them later on if we need them! ;-)

    printf("Hello World!n");
    This line calls our friend printf . It tells it to print "Hello World!" followed by a newline character (the n at the end).

    return 0;
    This line returns 0 back into our calling environment (in this case, it's our shell). If you don't know what returning values means or why you would want to do it, don't worry about it for now; just know that every C program must return a value back into its calling environment when it finishes running (we'll talk more about this later on in this tutorial).

1. Aim for newbies. Vastly under estimate the amount of explaining that must entail

2. Peter out somewhere between the first and second real code example