问题 单项选择题

操作系统作为一种系统软件,存在着与其他软件明显不同的三个特征是()。

A.可操作性、可视性、公用性

B.并发性、共享性、随机性

C.随机性、公用性、不可预测性

D.并发性、可操作性、脆弱性

答案

参考答案:B

解析:操作系统的三个特征是并发性、共享性、随机性。并发性是指两个或两个以上的事件或活动在同一时间间隔内发生;共享性是指操作系统中的资源(包括硬件资源和信息资源)可被多个并发执行的进程共同使用,而不是被一个进程所独占;随机性是指在多道程序环境中,允许多个进程并发执行,由于资源有限而进程众多,进程的执行不是一贯到底,而是“走走停停”。

阅读理解

阅读理解 .

       Hello, everyone, Here is something important for everyone going to London next month. As you

know, you are going to stay with a family for two weeks. Now, the most important thing is money. You

should take about 530 dollars with you. I think it will be enough for everyone. Then, when you arrive,

your new family will meet you. You must remember to wear a red shirt, so the family will find you easily.

They've been told you all wear red shirts. You'll also need to take with you 4 photos of yourself and, it's

also very important that you take the school letter. While you're there, if you have any problems, you can

call Leech School Office. I'll give you the office phone number: it's 580-4436 and the per-son to ask for

is Mrs Becher she is in the office from nine o'clock in the morning until five in the afternoon every day.

OK. That's everything. Have a good journey!

根据短文内容,回答下列问题。

1. Where are they going?

                                                                                      

2. How long are they going to stay there?

                                                                                     

3. Why must they wear red shirts?

                                                                                     

4. What could Mrs Becher's job be according to the passage?

                                                                                    

问答题