The writing Module. VI. Reading Exercises:

THE SPEAKING MODULE

After text activity

VI. Reading Exercises:

Exercise 1. Read and memorize using a dictionary:

Multiplexing, several, claimed identity, initial, linearly addressed memory system, associated, unaware, rate, descriptor register, interposed, a base value, a bound value, embellish, supervisor program, privileged state bit

Exercise 2. Answer the questions:

1) What is an example of a complete isolation system?

2) What does a typical computer consist of?

3) What is the essence of a multiprogramming system?

4) What is a descriptor register?

5) What is the privileged state bit?

Exercise 4. Match the left part with the right:

1 It is relatively easy to use a single computer to	a) simulate several, each of which is completely unaware of the existence of the others, except that each runs more slowly than usual.
2. Such a simulation is of interest, since during	b) a multiprogramming system.
3. Thus a single processor may be able to	c) the intervals when one of the simulated (commonly called virtual) processors is waiting for an input or output operation to finish, another virtual processor may be able to progress at its normal rate.
4. Such a scheme is the essence of	d) take the place of several.

II. Speaking Exercises:

Exercise 1. Define the terms using the suggested words and expressionsas in example:

Information science	Computer science	Data processing	Multiplexing
discipline, deals with, processes, storing,transferring, information	study, computers, computation, systems control, development, hardware, software, programming	conversion, raw, data, machine-readable form	process, transmitting, multiple, signals, simultaneously, single, channel,

EXAMPLE: Information science is a discipline that deals with the processes of storing and transferring information.

Exercise 2. Ask questions to the given answers:

1)Question: ___________________________________________?

Answer: If any running program could load it with any arbitrary value, there would be no protection.

2) Question: ___________________________________________?

Answer: One program (named the supervisor --program S in Fig. 1) runs with the privileged state bit ON, and controls the simulation of the virtual processors for the other programs.

3) Question: ___________________________________________?

Answer: Later we will extend our model of guards and walls in the discussion of shared information.

Writing exercises:

Exercise 1. Fill in the gaps with the suggested words:

Will, load, additional, to, state, with

The instruction that loads the descriptor register ____a new descriptor must have some special controls--either on the values it ____load or on who may use it. It is easier ____control who may use the descriptor, and a common scheme is to introduce an _______bit in the processor state. This bit is called the privileged state bit. All attempts to_____ the descriptor register are checked against the value of the privileged state bit; the privileged _____bit must be ON for the register to be changed.

Exercise 2. Compose a story on one of the topics (up to 100 words):

1) The multiplexing of a single computer system among several users

2) The authentication of a user's claimed identity

3) An isolated virtual machine

Lesson 7

Дата добавления: 2015-08-31