在分页式管理方式下采用位示图来表示主存分配情况，实现主存空间的分配和回收。

一个好的计算机系统不仅要有一个足够容量的、存取速度高的、稳定可靠的主存储器，而且要能合理地分配和使用这些存储空间-in pagination management practice adopted Bitmap to express distribution of main memory, main memory space realization of the distribution and recovery. A good computer system will not only have a sufficient capacity and access to the high-speed, reliable and stable main memory, and be able to make reasonable allocation and use of these storage space