#include <stdio.h>

 #include <stdlib.h>

 #include <math.h>

 int main()

 {

     //取整

     printf("%ld\n",(long)19.999);

     //保留0位小数部分

     printf("%.lf\n",19.999);

     //四舍五入

     //(long)是取整最右边的数据，而数据与数据之间以运算符号分开

     //所以一定要把数据和0.5用括号括起来，否则输出为0

     printf("%ld\n",(long)(19.5+0.5));

     printf("%ld\n",(long)(19.49+0.5));

     printf("%ld\n",(long)(19.51+0.5));

     //整型用abs，实型用fabs

     printf("%ld\n",abs(-));

     printf("%lf\n",fabs(-5.123));

     return ;

 }