实现首次适应算法的动态分配过程alloc（）和回收过程setfree（）。其中，空闲分区通过空闲区说明表；在进行内存分配时，系统优先使用空闲区低端的空间。-Algorithm to achieve the first time to adapt to the dynamic allocation process alloc () and the recycling process setfree (). Among them, the idle through the free zone Zoning Table　in memory allocation, the system is idle areas given priority in the use of low-end space.