这段程序能停止吗？unsigned int 的诱惑

john 2010-10-02 08:13:18

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

int main()
{
unsigned int i;

for(i=5; i>=0; i--)
{
printf("This is %d !\n",i);
getch();
}
return 0;
}

嘿嘿！试一试吧！

结果是：

This is 5 !
This is 4 !
This is 3 !
This is 2 !
This is 1 !
This is 0 !
This is -1 !
This is -2 !
This is -3 !
This is -4 !

... ...

无符号的整数他永远是无符号？

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/JohnPhan/archive/2010/08/03/5785511.aspx

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canshui 2010-10-03

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计算机是不认识什么类型的，例如int, char，这些类型针对与，程序员来说的才有意义的。

你把那些整数写成二进制的形式，也就是在内纯中的样子。这样在看看还有问题不

lly212 2010-10-03

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ctrl+c / ctrl +d

zff869030831 2010-10-02

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话说LZ我用的编译器可以判断出这个条件是永远为真，给出警告！

zhihuzhihuzhenyouqu 2010-10-02

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其实i一直是无符号的,但是经过printf("This is %d !\n",i);里面的"%d"这个,进行了转换,所以看到的是有负数出现的.如果改成printf("This is %u !\n",i);就可以了
能正常显示了,无符号>=0,必然无限循环,希望对lz有用

zhihuzhihuzhenyouqu 2010-10-02

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其实是printf("This is %d !\n",i);这句的问题....



#include <iostream>

#include <conio.h>

using namespace std;





int main(int argc, char* argv[])

{

	unsigned int i;

	

	for(i=5; i>=0; i--)

	{

		cout<<i<<endl;

		getch();

		

  }

	return 0;

}

漫步者、 2010-10-02

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[Quote=引用楼主 johnphan 的回复:]
include <stdio.h>
#include <stdlib.h>

int main()
{
unsigned int i;

for(i=5; i>=0; i--)
{
printf("This is %d !\n",i);
getch();
}
return 0;
}

嘿嘿！试一试吧！

结果是：

This is……
[/Quote]无符号的在机器中都是0、1表示，输出都以补码的形式输出的。

jznhljg 2010-10-02

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what's your point?

arong1234 2010-10-02

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如果不是这样还叫什么“无符号”，这不是无符号的定义么？[Quote=引用楼主 johnphan 的回复:]
include <stdio.h>
#include <stdlib.h>

int main()
{
unsigned int i;

for(i=5; i>=0; i--)
{
printf("This is %d !\n",i);
getch();
}
return 0;
}

嘿嘿！试一试吧！

结果是：

This is……
[/Quote]

xx说就叫这个名字 2010-10-02

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停不了的。。

john 2010-10-02

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...
This is 1 !
This is 0 !
This is 255 !
This is 254 !
...

说明了问题的本质。谢

cmlr_ 2010-10-02

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是.....
我用usigned char试了试,贴出部分结果
This is 26 !
This is 25 !
This is 24 !
This is 23 !
This is 22 !
This is 21 !
This is 20 !
This is 19 !
This is 18 !
This is 17 !
This is 16 !
This is 15 !
This is 14 !
This is 13 !
This is 12 !
This is 11 !
This is 10 !
This is 9 !
This is 8 !
This is 7 !
This is 6 !
This is 5 !
This is 4 !
This is 3 !
This is 2 !
This is 1 !
This is 0 !
This is 255 !
This is 254 !
This is 253 !
This is 252 !
This is 251 !
This is 250 !
This is 249 !
This is 248 !
This is 247 !
This is 246 !
This is 245 !
This is 244 !
This is 243 !
This is 242 !
This is 241 !
This is 240 !
This is 239 !
This is 238 !
This is 237 !
This is 236 !
This is 235 !
This is 234 !
This is 233 !
This is 232 !
的确如此,因为无符号数字永远不会小于0,所以就不断循环下去