blocks|key|106143|text|它与数据的内部表示有关。您正在尝试打印一个浮点数，就像它是一个int一样，它有一个完全不同的内部(二进制)表示。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|106144|double的情况与此类似。在float变量后面可能有垃圾(任何数据)。该垃圾被解释为双精度值的一部分。|offset|length|style|BOLD|106145|entityMap^0|0|0|6|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

It has to do with internal representations of data. You are trying to print a float as if it is an int, which has a completely different internal (binary) representation.

The double case is similar. You probably have garbage (any data) after the float variable. That garbage is interpreted as part of the double value.

blocks|key|2583542|text|由于变量参数的工作方式，除了%25d和%25f之外，C不知道您实际传递给它的值的类型。当你传入一个变量参数时，你基本上就是在做(void*)&myvalue，因为编译器和运行时的函数都不能确定变量的类型，除了格式化字符串中给出的类型。因此，即使有隐式转换可用，编译器也不知道需要它。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2583543|在大多数系统中，双精度是8个字节，而浮点数是4个字节。因此，这两种类型并不是二进制兼容的。这就像试图将字符串解释为双精度类型或其他不兼容的类型。|2583544|entityMap^0|E|2|H|2|1N|F|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

Because of the way variable parameters work, C has no idea of the type of value you are actually passing it other than <code>%d</code> and <code>%f</code>. When you pass in a variable parameter you are basically doing <code>(void*)&amp;myvalue</code> because neither the compiler, nor the function at run time can determine the type of the variable except for what is given in the formatting string. So even though there is an implicit conversion available, the compiler does not know it is needed. 

Well, double is 8 bytes on most systems while float is 4 bytes. So the two types are not binary compatible as it is. And it is like trying to interpret a string as a double, or some other incompatible type.

blocks|key|1173404|text|%25d代表decimal，它需要一个int类型的参数(或某种更小的有符号整数类型，然后提升)。浮点类型float和double都以相同的方式传递(提升为double)，并且它们都使用%25f。在C99中，您也可以使用%25lf来表示较大的double大小，但这纯粹是表面上的(请注意，在scanf中不会发生提升，这实际上会有所不同)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1173405|entityMap^0|0|2|H|3|1E|5|1K|6|23|6|2I|2|2X|3|36|6|3U|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|G|$]]

<code>%d</code> stands for decimal and it expects an argument of type <code>int</code> (or some smaller signed integer type that then gets promoted). Floating-point types <code>float</code> and <code>double</code> both get passed the same way (promoted to <code>double</code>) and both of them use <code>%f</code>. In C99 you can also use <code>%lf</code> to signify the larger size of <code>double</code>, but this is purely cosmetic (notice that with <code>scanf</code> no promotion occurs and this actually makes a difference).

blocks|key|105709|text|%25d打印一个整数，因此printf将变量a解释为int。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|105710|在gcc+3.4.6中，我在你的代码中两个值都是0(从a初始化中去掉F之后，因为这导致了一个编译器错误)。我怀疑这与a变量中被解释为int为0的部分有关，然后编译器就会感到困惑……(可能有更好的解释，但我想不出来)。|105711|为两个变量使用%25f，我会为两个变量打印1.000000。|105712|您可以在此页面底部附近找到转换字符的列表：|105713|http://www.exforsys.com/tutorials/c-language/managing-input-and-output-operations-in-c.html|offset|length|105714|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|0|2J|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@$J|X|K|Y|1|Z]]|A|$]]|$1|L|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|I]]]]

%d prints an integer, so your printf is interpreting your variable a as an int.

With gcc 3.4.6, I get 0's for both values with your code (after taking the F off the a initialization, as that led to a compiler error). I suspect this has to do with the part of the a variable that is being interpreted as an int being 0, and then the compiler gets confused ... (there's probably a better explanation, but I can't think of it).

Using %f for both variable prints 1.000000 for both variables for me.

You can find a list of the conversion characters near the bottom this page:

<a href="http://www.exforsys.com/tutorials/c-language/managing-input-and-output-operations-in-c.html" rel="nofollow noreferrer">http://www.exforsys.com/tutorials/c-language/managing-input-and-output-operations-in-c.html</a>

I was working on this program and I noticed that using %f for a double and %d for a float gives me something completely different. Anybody knows why this happens?

<pre><code>int main ()
{
 float a = 1F;
 double b = 1;

 printf("float =%d\ndouble= %f", a, b);
}
</code></pre>

This is the output

<pre><code>float = -1610612736
double = 190359837192766135921612671364749893774625551025007120912096639276776057269784974988808792093423962875123204096.0000
</code></pre>

C printf using %d and %f

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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我正在编写这个程序，我注意到，使用%f表示双精度型，使用%d表示浮点型，会给我带来完全不同的结果。有人知道为什么会这样吗？int main (){ float a = 1F; double b = 1; printf("float =%d\ndouble= %f", a, b);}这是输出float = -161061...

问C printf使用%d和%f
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