Is 'private' a C keyword?

Question

This question is merely to settle a wager, because I already know the answer and this seemed quicker than reading the standard:

Are 'private' or 'public' keywords in ANSI C (or any other C for that matter), or were they only added in C++ (and Java, C#, ...)?

Answer 1

private is not a C89 or C99 keyword. See C Programming/Reference Tables on Wikibooks*.

Also, C has nothing** to do with Java and C# (and, really, not C++ either). However, the converse is not true -- C++ grew from C, for example.

* Better reference needed!
** Actually, C89 "borrowed" the const and volatile keywords from C++. Likewise, C99 "borrowed" the inline keyword, and also added _Bool and _Complex (like C++'s bool andcomplex, respectively) ^{[citation-needed]}.

Answer 2

some people do:

• #define public
• #define private static

but it is not a C keyword.

EDIT:

For those who think it is a bad idea to do that, I would agree... but it does explain why someone might think "public" or "private" were C keywords.

For those who think it won't compile in C... try this:

#include <stdio.h>
#include <stdlib.h>

#define public
#define private static

private void sayHello(void);

public int main(void)
{
    sayHello();

    return (EXIT_SUCCESS);
}

private void sayHello(void)
{
   printf("Hello, world\n");
}

For those who think it won't compile in C++, yes the above program will. (Edit) Well actually it is undefined behaviour due to this part of the C++ standard:

A translation unit that includes a header shall not contain any macros that define names declared or defined in that header. Nor shall such a translation unit define macros for names lexically identical to keywords.

So the example above and below are not required to do anything sane in C++, which is a good thing. My answer still is completely valid for C (until is is proved to be wrong! :-)

In the case of C++ a class with private members you can do a similar (abuse) like this:

#include <cstdlib>
#define private public
#include "message.hpp"

int main()
{
    Message msg;

    msg.available_method();
    msg.hidden_method();

    return (EXIT_SUCCESS);
}

#ifndef MESSAGE_H
#define MESSAGE_H

#include <iostream>

class Message
{
private: 
    void hidden_method();

public: 
    void available_method();
};

inline void Message::hidden_method()
{
    std::cout << "this is a private method" << std::endl;
}

inline void Message::available_method()
{
    std::cout << "this is a public method" << std::endl;
}

#endif

Answer 3

No, C doesn't have encapsulation -- "information hiding". C++ and the other OOP languages introduced it.

Answer 4

The easiest way to settle this might have been to actually try using either with an ANSI/C89/C99 compiler (like gcc) :) A keyword needs no headers ;)