unsigned | 易学教程

why is char's sign-ness not defined in C?

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问题 The C standard states: ISO/IEC 9899:1999, 6.2.5.15 (p. 49) The three types char, signed char, and unsigned char are collectively called the character types. The implementation shall define char to have the same range, representation, and behavior as either signed char or unsigned char. And indeed gcc define that according to target platform. My question is, why does the standard do that? I can see nothing that can come out of ambiguous type definition, except of hideous and hard to spot bugs.

“strlen(s1) - strlen(s2)” is never less than zero

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问题 I am currently writing a C program that requires frequent comparisons of string lengths so I wrote the following helper function: int strlonger(char *s1, char *s2) { return strlen(s1) - strlen(s2) > 0; } I have noticed that the function returns true even when s1 has shorter length than s2 . Can someone please explain this strange behavior? 回答1: What you've come across is some peculiar behavior that arises in C when handling expressions that contain both signed and unsigned quantities. When an

“strlen(s1) - strlen(s2)” is never less than zero

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How to convert signed to unsigned integer in python

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问题 Let's say I have this number i = -6884376 . How do I refer to it as to an unsigned variable? Something like (unsigned long)i in C. 回答1: Assuming : You have 2's-complement representations in mind; and, By (unsigned long) you mean unsigned 32-bit integer, then you just need to add 2**32 (or 1 << 32) to the negative value. For example, apply this to -1: >>> -1 -1 >>> _ + 2**32 4294967295L >>> bin(_) '0b11111111111111111111111111111111' Assumption #1 means you want -1 to be viewed as a solid

Why doesn't C have unsigned floats?

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问题 I know, the question seems to be strange. Programmers sometimes think too much. Please read on... In C I use signed and unsigned integers a lot. I like the fact that the compiler warns me if I do things like assigning a signed integer to an unsigned variable. I get warnings if I compare signed with unsigned integers and much much more. I like these warnings. They help me to keep my code correct. Why don't we have the same luxury for floats? A square-root will definitely never return a

Why doesn't C have unsigned floats?

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TLV（1）定义

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TLV（1）定义 1. 定义 TLV（Type-Length-Value） 2. TLV的历史来源 3. TLV优缺点参考 1. 定义 TLV（Type-Length-Value） TLV 是一种常用的用于通信的结构体格式。 T表示 tag （类型） L表示 length （value的长度） V表示 value。其中T和L是固定大小的，V是可变大小，L表示的是V的长度。 2. TLV的历史来源紧凑模式写死的模式紧凑模式，意思是除了数据本身外，没有一点额外冗余信息，可以看成是Raw Data 例子是A和B通信，获取或设置基本资料，一般开发人员第一步就是定义一个协议结构: struct userbase { unsigned short cmd;//1-get, 2-set unsigned char gender; //1 – man , 2-woman, 3 - ?? char name[8]; //当然这里可以定义为 string name； } 可扩展性有一天，A在基本资料里面加一个生日字段，然后告诉B struct userbase { unsigned short cmd; unsigned char gender; unsigned int birthday ; char name[8]; } 这是B就犯愁了，收到A的数据包

Why does “int[] is uint[] == true” in C#

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问题 Can somebody clarify the C# is keyword please. In particular these 2 questions: Q1) line 5; Why does this return true? Q2) line 7; Why no cast exception? public void Test() { object intArray = new int[] { -100, -200 }; if (intArray is uint[]) //why does this return true? { uint[] uintArray = (uint[])intArray; //why no class cast exception? for (int x = 0; x < uintArray.Length; x++) { Console.Out.WriteLine(uintArray[x]); } } } MSDN's description does not clarify the situation. It states that

How to use the unsigned Integer in Java 8 and Java 9?

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问题 In the Oracle "Primitive data types" page, it mentions that Java 8 adds support for unsigned ints and longs: int : By default, the int data type is a 32-bit signed two's complement integer, which has a minimum value of −2 31 and a maximum value of 2 31 −1. In Java SE 8 and later, you can use the int data type to represent an unsigned 32-bit integer, which has a minimum value of 0 and a maximum value of 2 32 −1. Use the Integer class to use int data type as an unsigned integer. See the section

Signed versus Unsigned Integers

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问题 Am I correct to say the difference between a signed and unsigned integer is: Unsigned can hold a larger positive value, and no negative value. Unsigned uses the leading bit as a part of the value, while the signed version uses the left-most-bit to identify if the number is positive or negative. signed integers can hold both positive and negative numbers. Any other differences? 回答1: Unsigned can hold a larger positive value, and no negative value. Yes. Unsigned uses the leading bit as a part