11.strlen

#include<stdio.h>
#include<string.h>
#include<graphics.h>
int main()
{
	char buf[] = "hello";
	int len = strlen(buf);
	printf("%d", len);
	printf("%d", sizeof(buf));
	char buf2[] = "\0hello";//strlen从首元素到结束符
	int len2 = strlen(buf2);
	printf("%d", len2);
	printf("%d", sizeof(buf2));//sizeof()测试数据类型，不会因为\0而结束  

	char str[100] = "mile";
	printf("%d", sizeof(str));//4
	printf("%d", strlen(str));//100
}