question archive Question explain how the hardware and operating system support for paging combine to prevent one process from accessing another's memory
Question explain how the hardware and operating system support for paging combine to prevent one process from accessing another's memory
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Question explain how the hardware and operating system support for paging combine to prevent one process from accessing another's memory. [3 marks] (ii) Explain how space and time overheads arise from use of paging, and how the Translation Lookaside Buffer
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Number Of Loaded Publications
Add an integer to hold the number of Publications loaded into the PPA.
We will call this attribute "NOLP" for short, from now on.
Last Library Reference Number
Add an integer to hold the last library reference number read from the data file. This number will be used to assign new library reference numbers to new publications added to the library. When a new publication is added to the library, this number will be added by one and then assigned to the new publication. Doing this; each publication in the library will have a unique library reference number.
We will call this attribute "LLRN" for short, from now on. (b) How would you identify particular instances of data in order to record the information in a database? Illustrate your answer by considering both a relational database maintained using SQL-92 and an ODMG database. [6 marks] (c) A high street bank has just announced a merger with a nationwide building society. You are employed as a consultant to advise on the integration of their client databases. Both institutions use relational databases. Write brief notes to alert the database administrators to the difficulties that they may encounter. [8 marks] SECTION C 9 Semantics of Programming Languages (a) The integer expressions E of a programming language are given by E ::= n | X | −E | E + E where n ranges over integer constants and X ranges over identifiers. Explain the principle of structural induction for proving that some property Φ(E) holds for all integer expressions E. [5 marks] (b) Demonstrate the effect of concurrency control based on strict two-phase locking in relation to the discussion in (a). [8 marks] (c) Comment on the scope of concurrency control in relation to the discussion in (a). [5 marks] [Hint: you may assume that operat
Consider an operating system that uses hardware support for paging to provide virtual memory to applications. (a) (i) (TLB) mitigates the time overheads. [3 marks] (b) Consider a system with a five level page table where each level in the page table is indexed by 9 bits and pages are F1 is the set {A → D}. [2 marks] (ii) F2 is the set A, B → C E → B D, E → A [2 marks] (iii) F3 is the set A, B → C D, E → C A → D [4 marks] (b) We are given a relational schema R(Z, W, Y). Suppose that in some (correct) instance of R the query (πZ,W(R) ? πZ, R is not empty. What can we conclude about the functional dependency Z → W? Explain your answer. [4 marks] (c) In the process of using functional dependencies to normalise a schema, what is meant by a lossless join decomposition and how is such a decomposition guaranteed? [4 marks] (d) In schema normalisation, is Boyce-Codd Normal Form (BCNF) always to be preferred over 3rd Normal Form (3NF)? Explain your answer. [4 marks] 7 (TURN OVER) CST.2014.4.8 7 Economics, Law and Ethics (a) Describe the provisions of the Data Protection Act. [8 marks] 9 (TURN OVER) CST.2014.4.10 9 Security I Block ciphers usually process 64 or 128-bit blocks at a time. To illustrate how their modes of operation work, we can use instead a pseudo-random permutation that operates on the 26 letters of the English alphabet: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 m A B C D E F G H I J K L M N O P Q R S T U V W X Y Z EK(m) P K X C Y W R S E J U D G O Z A T N M V F H L I B Q As the XOR operation is not defined on the set {A, . . . , Z}, we replace it here during encryption with modulo-26 addition (e.g., C ⊕ D = F and Y ⊕ C = A). (a) Encrypt the plaintext "TRIPOS" using: (i) electronic codebook mode; [2 marks] (ii) cipher-block chaining.
