什么是无符号的字符？ [英] What is an unsigned char?

问题描述

在C / C ++，什么是 unsigned char型使用？如何从一个普通此不同的字符？

In C/C++, what is an unsigned char used for? How is this different from a regular char?

推荐答案

在C ++中，有三个的不同的的字符类型：

In C++, there are three distinct character types:

• 字符


• 符号字符


• unsigned char型

• char
• signed char
• unsigned char

如果您使用的是字符类型的文本的，使用不合格的字符：

If you are using character types for text, use the unqualified char:

• 这是字符文字像类型'一'或 0 。


• 这是构成C字符串喜欢的类型ABCDE

• it is the type of character literals like 'a' or '0'.
• it is the type that makes up C strings like "abcde"

它也可以作为一个数值，但它是未指定作为符号或无符号即值是否被处理。通过不平等谨防字符比较 - 但如果你限制自己的ASCII（0-127）你只是有关安全

It also works out as a number value, but it is unspecified whether that value is treated as signed or unsigned. Beware character comparisons through inequalities - although if you limit yourself to ASCII (0-127) you're just about safe.

如果您正在使用的字符类型为数字的，使用：

If you are using character types as numbers, use:

• 符号字符，它给你的至少的-127到127范围内。 （-128〜127是常见的）


• unsigned char型，它给你的至少的0到255范围内。

• signed char, which gives you at least the -127 to 127 range. (-128 to 127 is common)
• unsigned char, which gives you at least the 0 to 255 range.

至少，因为C ++标准只给每一个数字类型，需要覆盖值的最小范围。 的sizeof（char）的需要为1（即，一个字节），但一个字节在理论上可以是例如32位。 的sizeof 仍然会报告其大小为 1 - 这意味着你的可能的有无的sizeof（字符）==的sizeof（长）== 1 。

"At least", because the C++ standard only gives the minimum range of values that each numeric type is required to cover. sizeof (char) is required to be 1 (i.e. one byte), but a byte could in theory be for example 32 bits. sizeof would still be report its size as 1 - meaning that you could have sizeof (char) == sizeof (long) == 1.

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