一个C语言问题～～请教高手

[fllwt]

#include "stdio.h"
void main()
{ float b[10][10];
scanf("%f",&b[0][0]);
printf("%f",b[0][0]);
}
这个程序能编译并且运行成功
#include "stdio.h"
void main()
{ float b[10][10];
scanf("%f",&b[0][0]);
//printf("%f",b[0][0]);
}
为什么 这个就不行了呢？？？？
还有
#include "stdio.h"
void main()
{ float b[10][10];
scanf("%f",&b[0][0]);
b[0][0]=100;
}
这个也行，但是去掉后边一句就不行了 （ 自己分数不多，狠心发50了）

[fllwt]

请问你们的机子调试 都没问题么？

[NKLoveRene]

我刚才特意用dev c++试了

[fllwt]

[Quote=引用 11 楼 Chiyer 的回复:]
scanf
之前使用一下浮点运算，付值什么的都可以

比如

C/C++ code#include"stdio.h"voidmain()
{floatb[10][10]={0.0};
scanf("%f",&b[0][0]);
}
[/Quote]
记得书上说，如果数组不初始化，那么他们都被默认赋值为0，你所说的和书上说的冲突么？

[gaosen_bit]

// 加上这一句是避免连接器不载入c的运行时浮点库，参见《c专家编程》
float c = 1.f;

[fllwt]

[Quote=引用 13 楼 NKLoveRene 的回复:]
我刚才特意用dev c++试了
[/Quote]
刚才问了下别人，有出现这种情况的 而且我还换了台机子试试，还那样 我用的VC++ 我就郁闷了～！

[星羽]

这个现象叫 
Floating-point Support Not Loaded

vc6.0 和更老的版本会存在这个问题，vs2005 如果你使用c编译也可能存在这个问题，使用c++编译一般就正常
这个现象的表现是，如果你在使用scanf函数之前没使用过浮点运算，那么scanf就会出错

比如

#include <stdio.h>


int main()
{
    float x ;
    scanf ("%f", &x) ;
    return 0;

}



所以为了避免这个问题，你可以在scanf之前使用一下浮点运算

比如上面的改成

#include <stdio.h>


int main()
{
    float x = 0.f;
    scanf ("%f", &x) ;
    return 0;

}

就没问题了

[星羽]

我上面说的不一定全对，我记不清楚了，给你找了下ms的说法：

PRB: "Floating-point Support Not Loaded" Error with scanf()
View products that this article applies to.
Article ID	:	37507
Last Review	:	September 17, 2003
Revision	:	3.0
This article was previously published under Q37507
On This Page
SYMPTOMS
CAUSE
RESOLUTION
STATUS
MORE INFORMATION
Sample Code
SYMPTOMS
When an application uses the scanf() function to read a floating-point value from the console into an uninitialized "float" type global variable, an R6002 "floating-point format support not loaded" error occurs. This error also occurs when any formatted input routine is used to read a value.

Back to the top
CAUSE
The compiler does not generate a reference to the __fltused variable that instructs the linker to load the floating-point support module.

Back to the top
RESOLUTION
To work around this problem, initialize the floating-point variable or use the variable in an expression in the routine that contains the scanf() call.

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STATUS
This behavior is expected. To minimize the size of the executable file, the compiler loads floating-point support only when it is required.

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MORE INFORMATION
When a module uses only one of the formatted input routines and does not also initialize a floating-point variable, the compiler does not load floating-point support.

Remove the comment indication from either or both of the two lines in the sample code below to eliminate the R6002 error.

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Sample Code

   /*
    * Compile options needed: none
    */ 

   #include <stdio.h>
   float x ;

   main()
   {
   // Remove the comment from the next line to eliminate the error.
   // x = 2.3 ;

      scanf ("%f", &x) ;

   // Remove the comment from the next line to eliminate the error.
   // printf ("%f\n", x) ;
   }
				

Back to the top
APPLIES TO
•	The C Run-Time (CRT), when used with:
 	 	Microsoft C Professional Development System 6.0
 	 	Microsoft C Professional Development System 6.0a
 	 	Microsoft C Professional Development System 6.0a
 	 	Microsoft C Professional Development System 6.0
 	 	Microsoft C Professional Development System 6.0a
 	 	Microsoft C/C++ Professional Development System 7.0
 	 	Microsoft Visual C++ 1.0 Professional Edition
 	 	Microsoft Visual C++ 1.5 Professional Edition
 	 	Microsoft Visual C++ 5.0 Learning Edition
 	 	Microsoft Visual C++ 2.0 Professional Edition
 	 	Microsoft Visual C++ 4.0 Professional Edition
 	 	Microsoft Visual C++ 5.0 Professional Edition
 	 	Microsoft Visual C++ 6.0 Professional Edition

[fllwt]

原来是这样 呵呵，被他困扰了有一个多小时了 谢谢各位了 结分去了！^_^

[星羽]

http://support.microsoft.com/kb/q37507/

[fengdream]

我运行起来没有任何错误

C:\Documents and Settings\IBM_T23>vim main.c

gcc main.c
main.c: In function `main':
main.c:4: warning: return type of 'main' is not `int'

./a.out
1.2
1.200000

[fllwt]

[Quote=引用 20 楼 Chiyer 的回复:]
http://support.microsoft.com/kb/q37507/
[/Quote]
可是为什么
#include <stdio.h>
int main()
{ float b[10][10];

scanf("%f",&b[0][0]);
printf("%f",b[0][0]);
}
这样也是对的呢？
难道 它在调试时也先进行了浮点运算

[fllwt]

[Quote=引用 21 楼 fengdream 的回复:]
我运行起来没有任何错误

C:\Documents and Settings\IBM_T23>vim main.c

gcc main.c
main.c: In function `main':
main.c:4: warning: return type of 'main' is not `int'

./a.out
1.2
1.200000



[/Quote]
那就是我用的编译器的问题了 ^_^ 谢谢

[星羽]

http://support.microsoft.com/kb/q37507/
中文的 - -

[fllwt]

哦了 Chiyer说得对 呵呵 编译器的 问题 唉。。。以后还是尽量学LINUX吧^_^

[星羽]

msdn上的说法

Visual C++ Concepts: Building a C/C++ Program
C Run-Time Error R6002

Error Message
floating-point support not loaded

The necessary floating-point library was not linked.
To fix by checking the following possible causes

   1.

      The program was compiled or linked with an option, such as /FPi87, that requires a coprocessor, but the program was run on a machine that did not have a coprocessor installed.
   2.

      A format string for a printf_s or scanf_s function contained a floating-point format specification and the program did not contain any floating-point values or variables.
   3.

      The compiler minimizes a program's size by loading floating-point support only when necessary. The compiler cannot detect floating-point format specifications in format strings, so it does not load the necessary floating-point routines.
   4.

      Use a floating-point argument to correspond to the floating-point format specification, or perform a floating-point assignment elsewhere in the program. This causes floating-point support to be loaded.
   5.

      In a mixed-language program, a C library was specified before a FORTRAN library when the program was linked. Relink and specify the C library last.

[kingstarer]

这是TC的一个小bug，不能直接用scanf输出float二维数组元素

解决方法是先定义一个float temp；用scanf给temp赋值，然后用赋值语句将temp的值赋给二维数组元素

[chary8088]

无聊的问题
GCC运行正常

[skyell]

学到一个很好的经验，呵呵

[minimana]

原来是这样.当年学C时,我的老师只是说我的机器问题.那家伙正败类!

[liuciitc]

代码资料挺全,推荐一下:http://www.ciitc.com