char a [] =？string？有什么区别？和char * p =？string？;？ [英] What is the difference between char a[] = ?string?; and char *p = ?string?;?

问题描述

如标题所述，

之间的区别是什么？

  char a [] =？string？和
 char * p =？string ?; 
  

这个问题在面试中被问到我。
我甚至不理解语句。

  char a [] =？string？ 
  

这里是？它是一个字符串的一部分还是有一些特定的含义？

解决方案

第一个是数组另一个是指针。 / p>

数组声明 char a [6]; 请求留出六个字符的空格，名称 a 。也就是说，有一个名为 a 的位置，六个字符可以位于该位置。另一方面，指针声明 char * p; 请求一个保存指针的地方。指针可以通过名称 p 知道，并且可以指向任何地方的任何字符（或连续的字符数组）。

语句

  char a [] =string 
 char * p =string; 
  

会导致数据结构可以表示为：

  + --- + --- + --- + --- + --- + --- + ---- + 
a： | s | t | r | i | n | g | \0 | 
 + --- + --- + --- + --- + --- + --- + ---- + 
 + ----- + + --- + --- + --- + --- + --- + --- + --- + 
p：| * ======> | s | t | r | i | n | g | \0 | 
 + ----- + + --- + --- + --- + --- + --- + --- + --- + 
  

重要的是要意识到像 x [3] 是否 x 是一个数组或指针。给定上面的声明，当编译器看到表达式 a [3] 时，它会发出代码到 a ，移动三个元素通过它，并获取那里的字符。当它看到表达式 p [3] 时，它会发出代码到 p 在那里，向指针添加三个元素大小，最后获取指向的字符。在上面的例子中， a [3] 和 p [3] 恰好是字符 l ，但是编译器得到的不同。

资料来源： comp.lang.c常见问题清单·问题6.2

As the heading says, What is the difference between

char a[] = ?string?; and 
char *p = ?string?;  

This question was asked to me in interview. I even dont understand the statement.

char a[] = ?string?

Here what is ? operator? Is it a part of a string or it has some specific meaning?

解决方案

The first one is array the other is pointer.

The array declaration char a[6]; requests that space for six characters be set aside, to be known by the name a. That is, there is a location named a at which six characters can sit. The pointer declaration char *p; on the other hand, requests a place which holds a pointer. The pointer is to be known by the name p, and can point to any char (or contiguous array of chars) anywhere.

The statements

 char a[] = "string";
 char *p = "string"; 

would result in data structures which could be represented like this:

     +---+---+---+---+---+---+----+
  a: | s | t | r | i | n | g | \0 |
     +---+---+---+---+---+---+----+
     +-----+     +---+---+---+---+---+---+---+ 
  p: |  *======> | s | t | r | i | n | g |\0 |    
     +-----+     +---+---+---+---+---+---+---+ 

It is important to realize that a reference like x[3] generates different code depending on whether x is an array or a pointer. Given the declarations above, when the compiler sees the expression a[3], it emits code to start at the location a, move three elements past it, and fetch the character there. When it sees the expression p[3], it emits code to start at the location p, fetch the pointer value there, add three element sizes to the pointer, and finally fetch the character pointed to. In the example above, both a[3] and p[3] happen to be the character l, but the compiler gets there differently.

Source: comp.lang.c FAQ list · Question 6.2

这篇关于char a [] =？string？有什么区别？和char * p =？string？;？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！