取绝对值的时候，很多人知道用fabs()函数。但是这个函数是浮点函数，操作起来比较慢，特别是在嵌入式系统上面，大多数嵌入式系统都没有浮点预算单元，进行浮点模拟需要消耗大量的时间。这个程序使用的简单的办法-obtain absolute time, a lot of people know, fabs () function. However, this function is floating point function, operate more slowly, especially in embedded systems above, Most embedded systems do not have floating-point unit budget for floating point simulation consumed a lot of time. The procedure used a simple approach