#include#includeint main(void){int i;int sum=0;long n = clock();for(i=0;i<=100;i++){sum=sum+i;}n = clock()-n;printf("the sum from 1 to 100 is %d \n",sum);return 0;}n的值就是循环运行的时间,但是单位是机器周期,要换为秒的话要除以CLOCKS_PER_SEC,这个是宏定义的变量,可以直接用的