Explain how a parse tree representing an expression can (i) be converted into stack-oriented intermediate code. IN HERE ARE THE THINGS YOU HAVE TO CONSIDER BEFORE ANSWERING THE PROBLEM - (ii) be translated into simple machine code for a register-oriented architecture (e.g. ARM or IA32) on an instruction-by-instruction basis. Also indicate how this code might be 15 its successor and by notifying peer 12 that it should change its immediate successor to 13. DHTs have been finding widespread use in practice. For example, BitTorrent uses the Kademlia DHT to a distributed tracker. In the BitTorrent, the key is the torrent identifier and the value is the IP addresses of all the peers currently participating in the torrent [Falkner 2007, Neglia 2007]. In this manner, by querying the DHT with a torrent identifier, a newly arriving BitTorrent peer can determine the peer that is responsible for the identifier (that is, for tracking the peers in the torrent). After having found that peer, the arriving peer can query it for a list of other peers in the torrent. 2.7 Socket Programming: Creating Network Applications Now that we've looked at a number of important network applications, let's explore how network application programs are actually created. Recall from Section 2.1 that a typical network application consists of a pair of programsa client program and a server programresiding in two different end systems. When these two programs are executed, a client process and a server process are created, and these processes communicate with each other by reading from, and writing to, sockets. When creating a network application, the developer's main task is therefore to write the code for both the client and server programs. There are two types of network applications. One type is an implementation whose operation is specified in a protocol standard, such as an RFC or some other standards document; such an application is sometimes referred to as "open," since the rules specifying its operation are known to all. For such an implementation, the client and server programs must conform to the rules dictated by the RFC. For example, the client program could be an implementation of the client side of the FTP protocol, described in Section 2.3 and explicitly defined in RFC 959; similarly, the server program could be an implementation of the FTP server protocol, also explicitly defined in RFC 959. If one developer writes code for the client program and another developer writes code for the server program, and both developers carefully follow the rules of the RFC, then the two programs will be able to interoperate. Indeed, many of today's network applications involve communication between client and server programs that have been created by independent developersfor example, a Firefox browser communicating with an Apache Web server, or a BitTorrent client communicating with BitTorrent tracker. The other type of network application is a proprietary network application. In this case the client and server programs employ an application-layer protocol that has not been openly published in an RFC or elsewhere. A single developer (or 156 CHAPTER 2 APPLICATION LAYER development team) creates both the client and server programs, and the developer has complete control over what goes in the code. But because the code does not implement an open protocol, other independent developers will not be able to develop code that interoperates with the application a class that implementsthese two interfacesa program suppose, it is required to build a project consisting of a number of classes, possibly using a large number of programmers. It is necessary to make sure that every class from which all other classes in the project will be inherited. CST.2000.4.6 8 Computation Theory

Let N be the natural numbers {0, 1, 2 . . . What is meant by each of the following statements? The subset S N is recursive. The subset S N is recursively enumerable. [5 marks] [3 marks] program to compute the value of a given position in Pascal's Triangle (See image). Describe a data representation scheme for such trees in Prolog and demonstrate it by encoding the tree shown above Discuss. [4 marks] 6 CST.2004.3.8 9 Databases (a) We are given a relational schema R(A, B, C, D, E) and told that the following table represents a legal instance of R. A B C D E tuple number 1 2 5 4 3 (#1) 1 4 5 4 4 (#2) 2 4 5 4 5 (#3) 2 5 5 4 3 (#4) Which of the following sets of functional dependencies may hold in R? How well structured is the domain? What knowledge about the domain can be used to guide the search? Continuous Mathematics The complex form of the Fourier series is: where ck is a complex number and ck = ck. (a) Prove that the complex coeffiffifficient, ck, encodes the amplitude and phase coeffiffifficients, Ak and k, in the alternative form: An interprocess communication environment is based on synchronous message passing.