顺序档案转返 sequential file: 顺序文件; 序列文件rollback: 压平物价;击退。 default system for sequential file: 顺序文件的缺省系统demarcation of sequential file: 顺序文件定界; 顺序文件划分direct access sequential file: 直接存取顺序文件下载手机词典可随时随地查词查翻译