受到K&R第5.5节中描述的程序的启发：
void strcpy(char *s, char *t)
{
while(*s++ = *t++);
}
C 程序
if ('\0') { printf("\'\\0\' -> true \n"); }
else { printf("\'\\0\' -> false\n"); }
if ("\0") { printf("\"\\0\" -> true \n"); }
else { printf("\"\\0\" -> false\n"); }
打印
'\0' -> false
"\0" -> true
为什么
'\0'"\0"clang版本3.8.0
Stack Exchange 违反了此答案的许可条款，其显示此答案的许可证已被撤销。
首先，你需要记住，在C中，
NULLNULL'\0'0"\0"\0"\0"char* str = "string";因此，您正在有效地检查字符串文字的第一个字符的地址。由于字符串文字的地址始终为非
NULL†：数组的这种“衰变”并不总是发生。请参阅数组未衰减为指针的异常？
'\0'00!0但是
"\0"NULL首先看两个条件，
'\0'0"\0"NULL其次，在 C 中，对于
iftruefalse根据这个规则，可以明确
'\0'false"\0"true首先请注意，False 的十六进制值为
0x00"\0"'\0'['\0', '\0']编译后（未优化），这个字符指针被临时分配到内存中指向这两个字节的第一个字节的地址。例如，该地址可能是十六进制的
0x18A60x18A6 != false0x18A6 != 0x00'\0'0x000x00 != 0x00这个答案是针对具有 16 位寻址的 8 位数据架构编写的。我希望这有帮助。
' ' 是一个 null 字符，其值为 0。它用于终止一个字符串。所以它被认为是假的。
" " 是 null 或 empty string。字符串中唯一的字符是终止字符串的空字符。所以它被认为是 true。
' ' 是一个等于数字零的字符。 “”是一个字符串，我们通常在字符串末尾添加“”。不要在条件语句中使用 ' ' 或 " "，因为这很令人困惑。
建议使用以下方法：
if (array[0] != 0)
{
}
if (p != 0)
{
}
if (p != NULL)
{
}
通过示例查看此内容..
#include <stdio.h>
int main()
{
printf( "string value\n" );
//the integer zero
printf( "0.........%d\n" , 0 );
//the char zero, but chars are very small ints, so it is also an int
//it just has some special syntax and conventions to allow it to seem
//like a character, it's actual value is 48, this is based on the
//ASCII standard, which you can look up on Wikipedia
printf( "'0'.......%d\n" , '0' );
//because it is an integer, you can add it together,
//'0'+'0' is the same as 48+48 , so it's value is 96
printf( "'0'+'0'...%d\n" , '0'+'0' );
//the null terminator, this indicates that it is the end of the string
//this is one of the conventions strings use, as a string is just an array
//of characters (in C, at least), it uses this value to know where the array
//ends, that way you don't have to lug around another variable to track
//how long your string is. The actual integer value of '\0' is zero.
printf( "'\\0'......%d\n" , '\0' );
//as stated, a string is just an array of characters, and arrays are tracked
//by the memory location of their first index. This means that a string is
//actually a pointer to the memory address that stores the first element of
//the string. We should get some large number, a memory address
printf( "\"0\".......%d\n" , "0" );
//a string is just an array of characters, so lets access the character
//in position zero of the array. it should be the character zero, which
//has an integer value of 48
printf( "\"0\"[0]....%d\n" , "0"[0] );
//and the same thing for the empty string
printf( "\"\\0\"[0]...%d\n" , "\0"[0] ); //equal to '\0'
//we also said a string is just a pointer, so we should be able to access
//the value it is pointing to (the first index of the array of characters)
//by using pointers
printf( "*\"0\"......%d\n" , *"0" );
return 0;
}
简单的是，至少 0（int）和 0.0（float 或 double）在 C 中具有 FALSE 值。
' ' 是整数 0。
" " 是一个字符数组。数组内部有多少个字符或这些字符是什么并不重要。
因此，' ' 的计算结果为 0，就像 77-77 的计算结果为 0 一样。 0 为假。
int x;
x = '\0';
printf("X has a value : %d");
x 的值为：0
代码：
if(0){printf("true");}
else{printf("false");}
输出：
假