在理解指针之前，我们需要先理解对象。对象是存在的实体，具有一个称为地址的位置说明符。指针与C语言中的其他变量一样，是一个类型为指针的变量，其内容被解释为支持以下操作的对象的地址。

+ : A variable of type integer (usually called offset) can be added to yield a new pointer
- : A variable of type integer (usually called offset) can be subtracted to yield a new pointer
  : A variable of type pointer can be subtracted to yield an integer (usually called offset)
* : De-referencing. Retrieve the value of the variable (called address) and map to the object the address refers to.
++: It's just `+= 1`
--: It's just `-= 1`

指针是根据它当前引用的对象类型进行分类的。唯一重要的信息是物体的大小。

任何对象都支持& (address of)操作，该操作将对象的位置说明符(地址)作为指针对象类型检索。这将减少围绕命名的混乱，因为调用&作为对象的操作而不是作为结果类型为对象类型的指针的指针是有意义的。

注意:在整个解释中，我省略了内存的概念。

Come to think about it, I think it's a matter of semantics. I don't think the author is right, since the C standard refers to a pointer as holding an address to the referenced object as others have already mentioned here. However, address!=memory address. An address can be really anything as per C standard although it will eventually lead to a memory address, the pointer itself can be an id, an offset + selector (x86), really anything as long as it can describe (after mapping) any memory address in the addressable space.

指针是一种在C/ c++中本地可用的变量类型，包含一个内存地址。像任何其他变量一样，它有自己的地址并占用内存(数量是特定于平台的)。

由于混淆，您将看到的一个问题是试图通过简单地按值传递指针来更改函数中的引用。这将复制函数作用域内的指针，对这个新指针“指向”的地方的任何更改都不会改变调用该函数的作用域内指针的引用。为了修改函数中的实际指针，通常会将一个指针传递给另一个指针。

以下是我过去是如何向一些困惑的人解释的: 指针有两个影响其行为的属性。它有一个值(在典型环境中)是一个内存地址，还有一个类型(告诉您它所指向的对象的类型和大小)。

例如，给定:

union {
    int i;
    char c;
} u;

你可以有三个不同的指针都指向同一个对象:

void *v = &u;
int *i = &u.i;
char *c = &u.c;

如果你比较这些指针的值，它们都是相等的:

v==i && i==c

但是，如果对每个指针加1，就会发现它们所指向的类型变得相关了。

i++;
c++;
// You can't perform arithmetic on a void pointer, so no v++
i != c

此时，变量i和c将具有不同的值，因为i++使i包含下一个可访问的整数的地址，而c++使c指向下一个可寻址的字符。通常，整数比字符占用更多的内存，所以在它们都加一之后，i的值将比c的值更大。

很难确切地说出这些书的作者到底是什么意思。指针是否包含地址取决于如何定义地址和如何定义指针。

从所有的回答来看，有些人认为(1)地址必须是整数，(2)指针不需要是虚的，因为规范中没有这么说。根据这些假设，显然指针不一定包含地址。

然而，我们看到，虽然(2)可能是真的，(1)可能不一定是真的。根据@ corn秸秆的答案，&被称为操作符的地址，这是怎么回事?这是否意味着规范的作者希望指针包含地址?

我们可以说，指针包含一个地址，但地址不一定是整数?也许吧。

我认为所有这些都是废话连篇的迂腐语义学。实际上，这是毫无价值的。你能想到一个编译器以这样的方式生成代码，指针的值不是一个地址吗?如果有，是什么?我也是这么想的……

我认为这本书的作者(第一个摘录声称指针不一定只是地址)可能指的是指针自带固有类型信息这一事实。

例如,

 int x;
 int* y = &x;
 char* z = &x;

y和z都是指针，但y+1和z+1是不同的。如果它们是内存地址，难道这些表达式不会给你相同的值吗?

在这里，把指针当作地址的想法通常会导致悲伤。之所以会出现bug，是因为人们将指针视为地址，而这通常会导致不幸。

55555可能不是指针，尽管它可能是一个地址，但(int*)55555是一个指针。55555+1 = 55556，但是(int*)55555+1是55559(在sizeof(int)方面的+/-差异)。

简短的总结 (我也会把它放在顶部):

将指针视为地址通常是一个很好的学习工具，并且通常是普通数据类型指针的实际实现。

(1)但是在许多，也许是大多数编译器上，指向函数的指针不是地址，而是比地址大(通常是2倍，有时更多)，或者实际上是指向内存中结构体的指针，而不是包含函数地址和常量池之类的东西。

(2)指向数据成员的指针和指向方法的指针通常更奇怪。

(3)遗留的x86代码的FAR和NEAR指针问题

(4)几个例子，最著名的是IBM AS/400，具有安全的“胖指针”。

我相信你能找到更多。

细节:

UMMPPHHH ! !到目前为止，许多答案都是相当典型的“程序员菜鸟”答案——但不是编译器菜鸟或硬件菜鸟。因为我假装是一个硬件弱项，并且经常与编译器弱项一起工作，让我抛出我的意见:

在许多(可能是大多数)C编译器中，指向类型为T的数据的指针实际上是T的地址。

很好。

但是，即使在许多这样的编译器上，某些指针也不是地址。你可以通过sizeof(ThePointer)来判断。

For example, pointers to functions are sometimes quite a lot bigger than ordinary addresses. Or, they may involve a level of indirection. This article provides one description, involving the Intel Itanium processor, but I have seen others. Typically, to call a function you must know not only the address of the function code, but also the address of the function's constant pool - a region of memory from which constants are loaded with a single load instruction, rather than the compiler having to generate a 64 bit constant out of several Load Immediate and Shift and OR instructions. So, rather than a single 64 bit address, you need 2 64 bit addresses. Some ABIs (Application Binary Interfaces) move this around as 128 bits, whereas others use a level of indirection, with the function pointer actually being the address of a function descriptor that contains the 2 actual addresses just mentioned. Which is better? Depends on your point of view: performance, code size, and some compatibility issues - often code assumes that a pointer can be cast to a long or a long long, but may also assume that the long long is exactly 64 bits. Such code may not be standards compliant, but nevertheless customers may want it to work.

我们中的许多人都对旧的英特尔x86分段架构有痛苦的记忆，有NEAR指针和FAR指针。值得庆幸的是，这些几乎已经灭绝了，所以只有一个快速的总结:在16位实模式中，实际的线性地址是

LinearAddress = SegmentRegister[SegNum].base << 4 + Offset

而在保护模式下，它可能是

LinearAddress = SegmentRegister[SegNum].base + offset

with the resulting address being checked against a limit set in the segment. Some programs used not really standard C/C++ FAR and NEAR pointer declarations, but many just said *T --- but there were compiler and linker switches so, for example, code pointers might be near pointers, just a 32 bit offset against whatever is in the CS (Code Segment) register, while the data pointers might be FAR pointers, specifying both a 16 bit segment number and a 32 bit offset for a 48 bit value. Now, both of these quantities are certainly related to the address, but since they aren't the same size, which of them is the address? Moreover, the segments also carried permissions - read-only, read-write, executable - in addition to stuff related to the actual address.

A more interesting example, IMHO, is (or, perhaps, was) the IBM AS/400 family. This computer was one of the first to implement an OS in C++. Pointers on this machime were typically 2X the actual address size - e.g. as this presentation says, 128 bit pointers, but the actual addresses were 48-64 bits, and, again, some extra info, what is called a capability, that provided permissions such as read, write, as well as a limit to prevent buffer overflow. Yes: you can do this compatibly with C/C++ -- and if this were ubiquitous, the Chinese PLA and slavic mafia would not be hacking into so many Western computer systems. But historically most C/C++ programming has neglected security for performance. Most interestingly, the AS400 family allowed the operating system to create secure pointers, that could be given to unprivileged code, but which the unprivileged code could not forge or tamper with. Again, security, and while standards compliant, much sloppy non-standards compliant C/C++ code will not work in such a secure system. Again, there are official standards, and there are de-facto standards.

现在，我将放下我的安全演讲，并提到指针(各种类型)通常不是真正地址的其他一些方式:指向数据成员的指针，指向成员函数方法的指针，以及它们的静态版本比普通地址更大。正如这篇文章所说:

有许多方法可以解决这个问题[与单继承和多继承以及虚拟继承有关的问题]。Visual Studio编译器决定如何处理它:指向多重继承类的成员函数的指针实际上是一个结构。” 他们接着说:“强制转换函数指针可以改变它的大小!”

从我对安全性的评论中，您可能会猜到，我曾经参与过C/ c++硬件/软件项目，在这些项目中，指针更像是一种能力，而不是原始地址。

我还可以继续，但我希望你们能明白。

简短的总结 (我也会把它放在顶部):

(0)将指针视为地址通常是一个很好的学习工具，并且通常是普通数据类型指针的实际实现。

(1)但是在许多，也许是大多数编译器上，指向函数的指针不是地址，而是比地址大(通常是2X，有时更多)，或者实际上是指向内存中结构体的指针，而不是包含函数地址和常量池之类的东西。

(2)指向数据成员的指针和指向方法的指针通常更奇怪。

(3)遗留的x86代码的FAR和NEAR指针问题

(4)几个例子，最著名的是IBM AS/400，具有安全的“胖指针”。

我相信你能找到更多。