C++ cout 十六进制格式
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/3595136/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C++ cout hex format
提问by pdk
i am a c coder, new to c++.
我是 ac 编码员，刚接触 C++。
i try to print the following with cout with strange output. Any comment on this behaviour is appreciated.
我尝试使用带有奇怪输出的 cout 打印以下内容。对此行为的任何评论表示赞赏。
#include<iostream>
using namespace std;
int main()
{
unsigned char x = 0xff;
cout << "Value of x " << hex<<x<<" hexadecimal"<<endl;
printf(" Value of x %x by printf", x);
}
output:
输出：
Value of x ? hexadecimal
Value of x ff by printf
回答by Thanatos
<<handles charas a 'character' that you want to output, and just outputs that byte exactly. The hexonly applies to integer-like types, so the following will do what you expect:
<<处理char为您要输出的“字符”，并准确地输出该字节。该hex只适用于整数样的类型，所以下面会做你所期望的：
cout << "Value of x " << hex << int(x) << " hexadecimal" << endl;
Billy ONeal's suggestion of static_castwould look like this:
Billy ONeal 的建议static_cast如下：
cout << "Value of x " << hex << static_cast<int>(x) << " hexadecimal" << endl;
回答by Starkey
You are doing the hex part correctly, but x is a character, and C++ is trying to print it as a character. You have to cast it to an integer.
您正确地执行了十六进制部分，但 x 是一个字符，而 C++ 正试图将其打印为一个字符。您必须将其强制转换为整数。
#include<iostream>
using namespace std;
int main()
{
unsigned char x = 0xff;
cout << "Value of x " << hex<<static_cast<int>(x)<<" hexadecimal"<<endl;
printf(" Value of x %x by printf", x);
}
回答by Yeeson
If I understand your question correctly, you should expect to know how to convert hexto decsince you have already assigned unsigned char x = 0xff;
如果我正确理解您的问题，您应该知道如何转换hex为，dec因为您已经分配了unsigned char x = 0xff;
#include <iostream>
int main()
{
unsigned char x = 0xff;
std::cout << std::dec << static_cast<int>(x) << std::endl;
}
which shall give the value 255instead.
哪个应该给出值255。
Further detail related to the the strstream to decshall refer in http://www.cplusplus.com/reference/ios/dec/.
与str流相关的更多详细信息dec请参阅http://www.cplusplus.com/reference/ios/dec/。
If you want to know the hexadecimal value from the decimal one, here is a simple example
如果你想知道十进制的十六进制值，这里有一个简单的例子
#include <iostream>
#include <iomanip>
int main()
{
int x = 255;
std::cout << std::showbase << std::setw(4) << std::hex << x << std::endl;
}
which prints oxff.
打印oxff.
The library <iomanip>is optional if you want to see 0xahead of ff. The original reply related to hexnumber printing was in http://www.cplusplus.com/forum/windows/51591/.
<iomanip>如果您想0x提前查看该库，则该库是可选的ff。与hex数字打印相关的原始回复在http://www.cplusplus.com/forum/windows/51591/。
