函数strlen()和sizeof的区别：
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define SENTENCE "It is a cat"
int main()
{
char name[40];
gets(name);
printf("%s\n", name);
printf("The size of name is %zd %d\nThe size of SENTENCE is %zd %d",strlen(name), sizeof(name), strlen(SENTENCE), sizeof(SENTENCE));//请注意strlen()和sizeof的区别！
return 0;
}
strlen()函数是计算实际字符串的长度，而sizeof不但计算了字符串的大小，还记算了字符串末尾不可见的空字符!