关键字是预定义或保留的单词，在C ++库中可用，具有固定的含义，并且用于执行内部操作。C ++语言支持64个以上的关键字。
每个关键字都以小写字母形式存在，例如auto，break，case，const，continue，int等。
C ++语言中的32个关键字，也可用C语言提供。
auto | double | int | struct |
break | else | long | switch |
case | enum | register | typedef |
char | extern | return | union |
const | float | short | unsigned |
continue | for | signed | void |
default | goto | sizeof | volatile |
do | if | static | while |
这是30个不在C中但已添加到C ++中的保留字
asm | dynamic_cast | namespace | reinterpret_cast |
bool | explicit | new | static_cast |
catch | false | operator | template |
class | friend | private | this |
const_cast | inline | public | throw |
delete | mutable | protected | true |
try | typeid | typename | using |
using | using | wchar_t |
Input: str="for" Output: for is a keyword
关键字是保留字，不能在程序中用作变量名。
C编程语言中有32个关键字。
将字符串与每个关键字进行比较（如果字符串相同，则字符串为关键字）
#include <stdio.h>
#include <string.h>
int main() {
char keyword[32][10]={
"auto","double","int","struct","break","else","long",
"switch","case","enum","register","typedef","char",
"extern","return","union","const","float","short",
"unsigned","continue","for","signed","void","default",
"goto","sizeof","voltile","do","if","static","while"
} ;
char str[]="which";
int flag=0,i;
for(i = 0; i < 32; i++) {
if(strcmp(str,keyword[i])==0) {
flag=1;
}
}
if(flag==1)
printf("%s is a keyword",str);
else
printf("%s is not a keyword",str);
}输出结果
which is a keyword