Question:

Question 1

(a) In the evolution of imperative programming languages, features have been

introduced, whilst other features have been removed or deprecated in

'successor' languages.

Discuss, with critical comment, the motivations for these changes that have

been made to imperative programming languages. Concentrate your discussion

on issues of reliability and maintenance, both corrective and enhancement of

applications that are developed in these languages.

In your discussion use a range of imperative programming languages (For

example: COBOL, BCPL, C, C++, Java etc.) to illustrate points that you make.

DO NOT consider any issues or constructs that directly or indirectly make use

of concurrency.

(30 marks)

(b) Discuss, using an appropriate notation, how it is possible to 'port' a compiler for

a programming language to a new host machine which has a different

architecture from its existing environment. The effort required to port the

compiler should be considerably less that the effort required to create the

original version of the compiler.

In your discussion of the process involved, describe carefully the overall

structure of the compiler in relationship to the need to facilitate the 'port' of the

compiler to a new machine.

(20 marks)

Question 2
(a) What is transactional memory? Discus, how transactional memory may be
implicitly used in a Java program to improve performance in programs that
consist of several concurrently executing threads that share access to common
data structures.
Remember, the use of transactional memory will not require any changes to
the physical source code of a program.
(12 marks)
(b) Discuss, with critical comment, the extent to which the new features of Java 8
allow a programmer to construct a program that will make use of multiple cores
without explicitly having to use threads in the solution. Use appropriate
examples to illustrate the points that you make.
(26 marks)

 

(c) In a computer game, a high priority thread is used to process user interactions
with the system. This high priority thread accesses a shared data structure
(aSDS) which is also accessed by a low priority thread in the system. To
prevent corruption of the data, a lock is used to prevent more than 1 concurrent
access to the shared data structure (aSDS).
The low priority thread continually checks the state of the game and performs
low level housekeeping tasks including the re-organisation of the shared data
structure (aSDS). The re-organisation of the shared data structure (aSDS) will
occur every second, however, it will take under 5 CPU milliseconds to run.
The above system will always allow a higher priority thread to run even if it has
to pre-empt a running lower priority thread.
Recently a medium priority thread has been introduced that adds some artificial
intelligence to the game. This medium priority task takes some time to run (1-5
seconds), but can be pre-empted by the high priority thread that controls the
user interactions. The medium priority thread does not access the shared data
structure (aSDS).
Unfortunately the observed effect by users of the new version of the game is
that they occasionally experience long pauses of several seconds when it is not
possible to interact with the game.
Suggest what the most likely cause of this problem is in the new 'improved'
version of the game. Propose a solution to resolve the issue and carefully
comment on why it works.
(12 marks)

 

Question 3
(a) For systems that require authentication of users of the system, what steps
would you advise developers and users of the system to take to ensure as far
as possible that the users who are authenticated by the system really are the
person that they claim to be? For each suggestion, justify your selection with
critical comment about what issue or issues is being addressed.
In addition, what other issues would you advise the developers to investigate,
to ensure the confidentiality and security of the data stored on the system?
(30 marks)
(b) The TCP protocol provides a reliable stream-oriented communications medium,
and yet it uses the IP protocol suite, an unreliable packet-oriented medium.
Explain what 'reliable' means in this context, and describe how TCP's reliable
stream-oriented service is implemented.
Then explain and critically comment on the performance consequences of
using TCP to communicate between a client and a server when:
1) A long distance between the client and the server is involved.
2) A highly interactive program is used on the server, for example, a cloud
based editor which often involves the sending of single characters from
the client to the cloud based editor.
In each case above explain what can be/ is done to alleviate the impact on
performance.
(20 marks)

ComputerScienceExpert

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Status NEW Posted 25 May 2017 03:05 AM My Price 9.00

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