易安信笔试题

　　1 protected成员函数能被肿么调用

　　2 “has-a” relationship是指的啥，答案有instance, reference, pointer等。。。

　　3 int, char, short, long的字节数

　　4 在C++中，变量用时声明是为啥

　　5 命名空间的作用

　　6 int a[10][10];

　　int *b[10];

　　以下哪个正确

　　a[3][4] = 91;

　　b[3][4] = 91;

　　a[1] =NULL;

　　b[1] = a[2];

　　7 12&&10, 12||10, 12&10, 3>>1, 3>1的结果

　　8 x86_64系统下

　　struct

　　{

　　int i;

　　char c;

　　double d;

　　};

　　union

　　{

　　int i;

　　char c;

　　double d;

　　};

　　char s[100];

　　long c;

　　sizeof的值

　　10. An employee has one or two managers, and one manager manages one or more employees. In database conceptual design, the relationship between entity sets employee and manager is

　　A one to one

　　B one to many

　　C many to one

　　D many to many

　　E none of the above

　　11 There are two relations R1(A, B, C) and R2(B, D, E). Which of following techniques CANNOT be used to improve the performance of the natural join of the two relations?

　　A make use of multiple parallel processes on a multi-core machine to implement the join algorithm

　　B increase the CPU L2 cache hit ratio of the join algorithm implementation

　　C partition the relations to different machines by using join attributes and execute the join on many machines in parallel

　　D when the number of tuples in R2 is large and the number of tuples in R1 is small, build and index on R1 and use index join method

　　E none of the above

　　12 Which of the following statements about checkpoints(with log-based recovery schemes) in databases are/is NOT correct?

　　A checkpoints are used to decrease the time used for failure recovery

　　B checkpoints are done periodically in database to assure ACID properties of transactions

　　C periodic checkpoints decreased the number of log entries that need to be redone during recovery

　　D during checkpointing, updated disk blocks are written to disk

　　E none of the above