1、 了解系統調用fork()、execl()、exit()、getpid()和waitpid()的功能和實現過程
2、 編寫一段程序實現以下功能：
a) 使用系統調用fork()創建兩個子進程
b) 父進程重復顯示字符串”parent:”，并使用函數getpid()顯示自己的進程ID。
c) 兩個子進程分別重復顯示字符串”child:”，并使用函數getpid()顯示自己的進程ID
3、 編寫一段程序實現以下功能：
a) 使用系統調用fork()創建一個子進程
b) 子進程顯示自己的進程ID和字符串": The child is calling an exec.\n"，然后通過execl()調用系統命令ps顯示當前運行的進程情況，從而更換自己的執行代碼，最后調用exit()結束。
c) 父進程顯示自己的進程ID和字符串” ": The parent is waiting for child to exit.\n "，然后調用waitpid()等待子進程結束，并在子進程結束后顯示”The parent exit.\n
This project attempts to implement a Database using B+Tree. The project has developed a DATABASE SYSTEM with lesser memory consumption. Its API includes simple SQL Statements and the output is displayed on the screen. Certain applications for which several features of existing databases like concurrency control, transaction management, security features are not enabled. B+Trees can be used as an index for factor access to the data. Help facility is provided to know the syntax of SQL Statements.
