主索引目录程序文件是为震源参数数据文件epc建立一个索引目录的数据记录。有了它之后,在检索任何一个数据文件时,只要先查看该目录,就可以按照它所指定的epc数据记录的编号去直接读取数据记录。因此,就不必对数据文件的每一个数据记录从头至尾地访问一遍,节省了检索数据的机器时间和减少了磁盘(或磁带)的读取次数。显然,主索引目录有助于提高数据的查找效率。它也是数据文件管理方式的重要组成部分。 The main index directory program files for the source parameter data file epc create an index directory data records. With it, when you retrieve any data file, you just read the directory first, and you can read the data record directly according to the number of the epc data record it specifies. Thus, it is not necessary to access each data record of the data file from the beginning to the end, saving the time for retrieving the data and reducing the number of times the disk (or tape) is read. Obviously, the main index directory helps to improve data search efficiency. It is also an important part of the way data files are managed.