to judge what kinds of links of files and recursive subdir if option -r chosen, and display the link information. usage: lk [options] [directory list ...], input options (broken soft links by default) and dirctory lists (current directory by default)

实现进程的软中断通信。 使用系统调用fork()创建两个子进程，再用系统调用signal()让父进程捕捉键盘上来的中断信号（即DEL键）；当捕捉到中断信号后，父进程用系统调用kill()向两个进程发出信号，子进程捕捉到信号后分别输出下列信息后终止： Child Process 1 is Killed by Parent! Child Process 2 is Killed by Parent! 父进程等待两个子进程终止后，输出如下信息后终止： Parent Proce

菜单栏：数据录入（信息录入；成绩录改）/计算（总平均分；总分最高；总分最低；分科目及格率）/操作（查询，修改，删除）/帮助（关于个人信息显示）/总人数统计/软键盘写入/性别选择为（男、女）复合框-Menu bar: data entry (entry information results recorded change)/calculation (the overall average score the highest total score Total minimum points