为什么这个循环在c中运行无限次？ [英] why this loop is running infinite times in c?

问题描述

我只是在C编程中试验一个代码。并来了解一个奇怪的行为。
那么...因为我不是C上的专家，所以我不知道它是奇怪的还是正常的。

基本上我的问题是关于以下两行代码之间的区别： -

  char a ='h'; //这里变量a不是char数组
  

和$ /

  char a ='hi'; //这里的变量a也不是一个char数组（不知道编译器是否把它当作一个数组，但至少我没有这样声明）
  

我使用了下面的代码：

第一个： -

  char a = 0; $; 
 for（; a<'hi'; a ++）
 {
 printf（％d = hello world \\\
，a）; 
 
 $ / code> 

第二：



  char a; （a ='h'; a<'hi'; a ++）
 {
 printf（％d = hello world \\\
，a）的
。 
 
 $ / code> 

上面提到的两个循环都会一直运行，

有人可以告诉我为什么吗？

我可能会错过一个非常基本的编程概念。请帮助我们

解决方案

那是因为'hi' int 不是 char 。它也解析为值26729.但最可能的循环变量（假设 char 为1字节类型，字节为8位）受127限制，之后溢出。注意这个：

  char a = 0; 
 
 
 
 char m ='hi'; （; a  {
 printf（％d = hello world \\\
，a）
; 
 
 $ / code $ 
 
 
 
可以工作，因为'hi'将被强制转换为char（105）。
 $ b 
 'hi'是一个多字符字面值。在编程中并不常见，它是C99标准的一部分的不为人知的C特征。更多关于它们的信息： http://zipcon.net/~swhite/ docs / computers / languages / c_multi-char_const.html  
 
I was just experimenting a code in C programming. and came to know a strange behavior.
Well... Since i am not an expert on C, so i don't know whether its strange or normal.

Basically my question is all about the difference between the following two lines of code:-
char a = 'h'; // here variable a is not an array of "char"
and
char a = 'hi'; //here variable a is not an array of "char" as well (i don't know if compiler assumes it as an array or not but , at least i didn't declared it that way )
I used the following codes

first:-
char a =0;
for(;a<'hi';a++)
{
    printf("%d= hello world \n",a);
}
second:-
char a;
for(a='h';a<'hi';a++)
{
    printf("%d= hello world \n",a);
}
both of the above mentioned loops keep running forever,

Can somebody tell me why so ?

I might be missing a very basic concept of programing. please help me guys
解决方案
That is because 'hi' has type int not a char. It also resolves to value 26729. But loop variable most likely (assuming char is 1-byte type and byte has 8 bits) is limited by 127 and after that overflows.

Note that this:
char a =0;
char m = 'hi';
for(; a < m; a++)
{
    printf("%d= hello world \n",a);
}
will work because 'hi' is will be coerced to char (105).

'hi' is a multi-character literal. It is not common practice in programming, it is "less known" C feature which became part of C99 standard. More information about them: http://zipcon.net/~swhite/docs/computers/languages/c_multi-char_const.html 

                        
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