操作系统

若一个逻辑顺序文件中记录数为n。试从检索速度（平均查找次数）、存储费用和适用场合方面比较顺序文件、索引文件、索引顺序文件和两级索引文件。并要求说明索引顺序文件的平均查找次数。-If the operating system is a logical sequence of records in the file number n. From the retrieval speed test (average seek times), storage costs, and where applicable with relatively sequential files, index files, indexed sequential files, and two index files. And asked for clarification of the average indexed sequential file lookups.