A、<font face="宋体">机器指令</font><span lang="EN-US"><span style="mso-spacerun: yes"></span></span>
B、<font face="宋体">系统调用命令</font>
C、<font face="宋体">作业控制命令</font><span lang="EN-US"><span style="mso-spacerun: yes"></span></span>
D、<font face="宋体">低级进程通信原语</font>