blocks|key|2974544|text|stdio代表标准输入/输出。顾名思义，它包含了与标准IO相关的东西。Wikipedia+article+of+stdio.h列出了stdio.h的内容。如果使用它们，您将需要stdio.h。您也可以查看man+page+of+stdio.h以了解更多详细信息。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2974545|而对于操作系统部分，编写操作系统远不止是简单的编程，即使它是一个学术编程。在开始之前，你应该学习数据结构，算法，操作系统理论等等。The+Design+of+the+UNIX+Operating+System是一本很好的学习操作系统的书。Nachos是一个学术版的操作系统模拟程序。你也可以检查一下。如果你对操作系统着迷，那么你应该读一读Linus+Torvalds+Just+for+Fun的自传。好吧，这不是一本技术书籍，但你会有一种感觉，它意味着编写一个操作系统。|2974546|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Stdio.h|1|http://www.manpagez.com/man/3/stdio/|2|https://rads.stackoverflow.com/amzn/click/com/0132017997|3|http://en.wikipedia.org/wiki/Not_Another_Completely_Heuristic_Operating_System|4|https://rads.stackoverflow.com/amzn/click/com/0066620724^0|0|5|Z|S|0|2U|J|1|0|1T|13|2|3B|6|3|54|C|4|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@$9|10|A|11|1|12]|$9|13|A|14|1|15]]|E|$]]|$1|F|3|G|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]|$9|1A|A|1B|1|1C]|$9|1D|A|1E|1|1F]]|E|$]]|$1|H|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]|R|$5|K|L|M|E|$N|S]]|T|$5|K|L|M|E|$N|U]]|V|$5|K|L|M|E|$N|W]]]]

<code>stdio</code> stands for Standard Input/Output. As the name said, it contains things related to standard IO. The <a href="http://en.wikipedia.org/wiki/Stdio.h" rel="nofollow noreferrer">Wikipedia article of stdio.h</a> lists the contents of stdio.h. You will need stdio.h if you use them. And you can check the <a href="http://www.manpagez.com/man/3/stdio/" rel="nofollow noreferrer">man page of stdio.h</a> too for further details. 

And for the OS part, writing an OS is much more than simple programming, even if it is an academic one. Before jumping to that you should learn data structures, algorithms, OS theories and much more. <a href="https://rads.stackoverflow.com/amzn/click/com/0132017997" rel="nofollow noreferrer" rel="nofollow noreferrer">The Design of the UNIX Operating System</a> is a very good book to learn OS. <a href="http://en.wikipedia.org/wiki/Not_Another_Completely_Heuristic_Operating_System" rel="nofollow noreferrer">Nachos</a> is an academic OS simulation program. You can check that too. And if you are fanatic about OS, then you should read the autobiography of Linus Torvalds <a href="https://rads.stackoverflow.com/amzn/click/com/0066620724" rel="nofollow noreferrer" rel="nofollow noreferrer">Just for Fun</a>. Well, it's not a technical book, but you will get a feeling what it means writing an OS.

blocks|key|3260480|text|任何引导加载器几乎肯定会有#include指令，除非它设计得很差。我不知道你从哪里得到这句话的，但也许你误解了它。引导加载器总是从一段纯汇编代码开始，用于初始的低级处理器初始化和初始化C运行时环境。这段代码根本不可能用C语言编写，但其余的代码可以根据需要在环境(内存等)的限制下变得非常复杂。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3260481|stdio只是一组连接到某种设备的文件流，这些设备可以接收输入和输出。您可以实现stdin、stdout、stderr或它们的任何子集。您还可以实现一个可以打开任意文件流的文件系统。在现代操作系统中，这最终连接到某种类型的终端，这通常涉及到相当多的层之间，因为它是显示在您的显示器上的虚拟终端，因此需要图形驱动程序等。在原始的嵌入式系统中，stdio可能连接到串行端口或LED显示器。|3260482|stdio使用read()和write()函数实现。如果没有实现这些，你就不能使用printf()、fprintf()、fgets()等stdio函数，这并不意味着你不能写到你的图形显示器、串口或其他任何东西上。这只是意味着您没有标准的工具来执行此操作，需要调用自定义函数。|offset|length|style|CODE|3260483|回答你的问题:没有stdio，你可以用C做任何事情。无论如何，它都是用C编写的，你只是失去了一些在任何C标准库中实现的通用功能。|3260484|entityMap^0|0|0|7|6|E|7|15|8|1E|9|1O|7|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|P|8|@$F|Q|G|R|H|I]|$F|S|G|T|H|I]|$F|U|G|V|H|I]|$F|W|G|X|H|I]|$F|Y|G|Z|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|10|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|M|$]]

Any bootloader will almost certainly have #include directives, unless it is poorly designed. I don't know where you got that quote, but perhaps you misunderstood it. A bootloader will invariably start with a piece of pure assembly code for the initial low-level processor initialization and to initialize the C runtime environment. This code is simply not possible to write in C. But the rest of the code can be as complex as needed, within the restrictions of the environment (memory, etc).

stdio is simply a set of file streams connected to some kind of device which can receive input and output. You can implement stdin, stdout, stderr or any subset of them. You also may implement a filesystem for which you can open arbitrary file streams. In a modern OS, this ends up connected to some kind of terminal typically, which involves quite a bit of layers in-between because it's a virtual terminal that shows up on your monitor and thus requires a graphics driver and so forth. On a primitive embedded system, stdio might be connected to a serial port, or an LED display.

stdio is implemented with the <code>read()</code> and <code>write()</code> functions. If these are not implemented, you simply can't use the stdio functions like <code>printf()</code>, <code>fprintf()</code>, <code>fgets()</code>, etc. That doesn't mean you can't write to your graphics display, serial port or whatever else. It just means you don't have a standard facility to do so and will need to call custom functions.

To answer your question: you can do anything in C without stdio. It's all written in C anyway, you're just losing some common functionality implemented in any C standard library.

blocks|key|2974646|text|正如taskinoor提到的那样，维基百科提供了一个很好的参考资料，介绍了stdio.h中包含的内容。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2974647|至于没有stdio.h的可能性，几乎所有使用它的可能性，尽管你必须为某些事情付出更多的努力。例如，如果你想使用文件，你将不得不定义你自己的文件抽象，以及你自己的处理它的接口。如果您想从键盘读取输入，那么您将不得不使用汇编代码来调用scanf()中断，而不是调用BIOS。|style|CODE|2974648|这就是操作系统编程的本质。在您定义这些更高级别的构造和使用它们的API之前，它们都不存在。您需要从最小的基本功能开始，并开始将它们分组在一起，以创建越来越有用和复杂的结构。|2974649|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Stdio.h^0|11|7|0|0|37|7|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@$A|W|B|X|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|Y|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|K|$L|$5|M|N|O|C|$P|Q]]]]

As taskinoor mentions, Wikipedia provides an excellent reference about what is included in <a href="http://en.wikipedia.org/wiki/Stdio.h" rel="nofollow">stdio.h</a>.

As for what's possible without stdio.h, pretty much everything that is possible with it, although you will have to work a lot harder for certain things. If you want to use files, for instance, you will have to define your own abstraction of a file, and your own interface for working with it. If you want to read input from the keyboard then instead of calling <code>scanf()</code> you'll have to use assembly code to call a BIOS interrupt. 

Such is the nature of programming an OS. None of these higher-level constructs exist until you define them and the API for working with them. You need to start with the smallest basic pieces of functionality, and start grouping them together to create increasingly more useful and complex constructs.

blocks|key|3260595|text|C标准(ISO/IEC+9899:1999)认可两种类型的实现(§4一致性，²6)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3260596|3260597|独立-其中实现(编译器和库)仅提供七个头文件：|unordered-list-item|3260598|3260599|++++++|3260600|它们为语言提供了基本的功能，并且没有声明任何函数(+<stdarg.h>中的功能在标准中被显式定义为宏)。请注意，它不包括复杂的numbers.|offset|length|style|CODE|3260601|Hosted+-其中的实现提供了由标准定义的完整的库。|3260602|3260603|独立实现的全部要点是允许您编写所需的任何代码，而不受通常的标准库和特定的标准I/O函数的限制。缺点是，您不仅可以而且必须提供这些功能-或者利用实现提供的替代功能。请注意，在独立实现中，程序的入口点不需要称为main。|3260604|您正在寻找的是独立的实现--或者使用托管实现的独立部分。您将使用头文件(除非您疯了)，但它们可能不是标准的C库头文件，而不是列出用于独立实现的其他文件。|3260605|entityMap^0|0|0|0|0|0|Q|A|0|0|0|2V|4|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Z|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|11|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|12|8|@$K|13|L|14|M|N]]|9|@]|A|$]]|$1|O|3|P|5|E|7|15|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|17|8|@$K|18|L|19|M|N]]|9|@]|A|$]]|$1|T|3|U|5|6|7|1A|8|@]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|W|$]]

The C standard (ISO/IEC 9899:1999) recognizes two types of implementation (§4 Conformance, ¶6):

<ul>
<li>Freestanding - where the implementation (compiler plus library) only provides seven headers:

<pre><code>&lt;float.h&gt;
&lt;iso646.h&gt;
&lt;limits.h&gt;
&lt;stdarg.h&gt;
&lt;stdbool.h&gt;
&lt;stddef.h&gt;
&lt;stdint.h&gt;
</code></pre>

These provide basic facilities for the language and declare no functions (the facilities in <code>&lt;stdarg.h&gt;</code> are explicitly defined as macros in the standard). Note that it does not include complex numbers.</li>
<li>Hosted - where the implementation provides the complete library defined by the standard.</li>
</ul>

The whole point of a freestanding implementation is to allow you to write any code you need unencumbered by the standard library in general, and the standard I/O functions specifically. The downside is that you not only can but must provide those functions - or make use of alternatives provided by the implementation. Note that in a freestanding implementation, the entry point for the program need not be called <code>main</code>.

What you are seeking is a freestanding implementation - or to use the freestanding portion of a hosted implementation. You will use headers (unless you're insane), but they probably won't be the standard C library headers other than those listed for use with a freestanding implementation.

blocks|key|2974782|text|关于最小C环境的其他答案都很好，但这里有另一个更抽象的角度。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2974783|C标准定义了两种“可观察到的副作用”，这基本上意味着你的程序所做的事情是不能被编译器优化或修改的。它们首先是对I/O函数的调用，其次是对volatile对象的读取和写入。|offset|length|style|CODE|2974784|如果您不能访问stdio或依赖于操作系统的C实现的其他部分，就不能使用I/O函数。这使得对volatile对象的读取和写入成为您的程序真正“做”的唯一事情。在实践中，您可能需要也可能不需要将所有内容都标记为volatile，因为您的C实现可能提供了超出标准的保证。如果有一条CPU指令发出蜂鸣声，您的编译器会将其(以及一般的内联汇编)视为I/O函数，即使它不是真正的函数，依此类推。|2974785|换句话说，您将不得不使用低级硬件访问来实现引导加载程序应该实现的目标(这相当于:在屏幕上显示一条消息，建立操作系统运行所需的一些资源，加载并运行它)。当然，这种访问完全依赖于实现-硬件供应商可能会提供库来帮助您，只是它们不是标准的C头文件。|2974786|entityMap^0|0|1W|8|0|7|5|19|8|2V|8|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@$D|S|E|T|F|G]|$D|U|E|V|F|G]|$D|W|E|X|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|Y|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|M|$]]

The other answers about minimal C environments are good, but here's another more abstract angle.

The C standard defines two kinds of "observable side-effects", which basically means things your program does that cannot be optimized away or otherwise modified by the compiler. These are firstly calls to I/O functions, and secondly reads and writes of <code>volatile</code> objects.

If you don't have access to <code>stdio</code> or other parts of your C implementation that rely on the presence of the OS, you can't use I/O functions. That leaves reads and writes to <code>volatile</code> objects as the only things that your program will actually "do". In practice, you may or may not have to actually mark everything <code>volatile</code>, since your C implementation probably provides guarantees beyond the standard. If there's a CPU instruction that makes a beep noise, your compiler will treat that (and inline assembly in general) like an I/O function even though it's not really a function, and so on.

In other words, you will have to use low-level hardware access to achieve whatever it is your bootloader is supposed to achieve (which amounts to: display a message on screen, establish some resources that the OS needs in order to run, load it and run it). This access is of course entirely implementation-dependent - hardware vendors might provide libraries to help you, they just won't be the standard C headers.

I've been interested in programming an operating system for some time. Delving through a few different sites, I've come across an interesting concept (to paraphrase): if you start writing your bootloader with #include, you've already made a fatal mistake. 

I've gone through K&amp;R, and the entire book includes it throughout each lesson. Having used it throughout learning C, I don't know what I've learned that uses stdio and what doesn't. What can you do in C without stdio?

C without stdio, what is possible?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我对编写操作系统很感兴趣已经有一段时间了。在深入研究几个不同的站点时，我发现了一个有趣的概念(转述一下)：如果您使用#include开始编写引导加载程序，那么您已经犯了一个致命的错误。我已经经历了K&R，整本书在每一课中都包含了它。在学习C语言的过程中，我一直在使用它，我不知道我学到了什么可以使用stdio，哪些不可以...

问没有stdio，什么是可能的？
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