For each of the four techniques in part (iv), suggest a method by which some of the resulting information could be obtained earlier in the project. Ensure that your answer explains when locks are acquired and released. [8 marks] (v) A future is a mechanism to store the eventual result of a computation done in another thread. The idea is that the computation is run asynchronously and the calling thread only blocks if it tries to use a result that hasn't been computed yet. The object of the search is to find a path from the initial state to a goal state using a tree. The number of nodes generated might be huge; and in practice many of the nodes would not be needed. The secret of a good search routine is to generate only those nodes that are likely to be useful, rather than having a precise tree. The rules are used to represent the tree implicitly and only to create nodes explicitly if they are actually to be of use. The following issues arise when searching: The tree can be searched forward from the initial node to the goal state or backwards from the goal state to the initial state. To select applicable rules, it is critical to have an efficient procedure for matching rules against states. How to represent each node of the search process? Computer Design (a) What is a pipeline bubble and why might a branch instruction introduce one or more bubbles? [4 marks] (b) Explain, with the aid of an example, how conditional instructions may be used to reduce the number of bubbles in a pipeline. [4 marks] (c) What is the difference between branches, interrupts, software interrupts (initiated by a SWI instruction on the ARM) and exceptions? [8 marks] (d) What is an imprecise exception and why might a processor designer prefer it to a precise exception mechanism?

Digital Communication I Information is to be conveyed from A to B using automatic repeat request (ARQ), forward error correction (FEC), and lossless compression. (a) Explain the terms ARQ, FEC and lossless compression. [5 marks] (b) If we consider each of these functions to be operating at different protocol layers, what would be the most sensible ordering of the layers, and why? [5 marks] (c) Suppose: The underlying bit channel has a capacity of B, a delay and error rate 0. The compression ratio is C < 1. The FEC has rate R < 1 and given an error rate 0 provides an error rate 1 (which is detected). The ARQ protocol has a window size of W. At what rate can the information be conveyed? [Hint: Consider when retransmissions are made.] State any assumptions you about the operation of the ARQ protocol.

4 Computer Graphics and Image Processing (a) Describe the limitations of human vision in terms of: (i) spatial resolution (ii) luminance (iii) colour and explain the implications that each of these limitations has on the design of display devices. [10 marks] (b) In image compression we utilise three different mechanisms to compress pixel data: (i) mapping the pixel values to some other set of values (ii) quantising those values (iii) symbol encoding the resulting values Explain each mechanism, describe the way in which it helps us to compress the image, and describe in what way it affects the visual quality of the resulting (decompressed) image when compared with the original. [10 marks] SECTION B 5 Comparative Programming Languages (a) Outline the main innovations that are in Simula 67 but were not in Algol 60, paying particular attention to Simula Classes. [6 marks] (b) Illustrate how Simula can be used to simulate a small restaurant with six tables, two waiters and small groups of customers arriving at random intervals. You need specify only the classes you would define. Most of the algorithmic details may be omitted. [6 marks] (c) Discuss to what extent Simula has been made redundant by the development of modern object-oriented languages such as Java.

Databases (a) Explain how to describe the structure of a collection of data using entities, attributes and relationships. [6 marks]