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FIRST PRELIMINARY EXAMINATION NOVEMBER 2018 COMPUTER SCIENCE Paper - 1 (THEORY) Class: XII - ISC Marks: 70 Time: 3 Hrs. Date: 30/11/2018 (Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time) _________________________________________________________________________________ Answer all questions in Part I (compulsory) and six questions from Part-II, choosing two questions from Section-A, two from Section-B and two from Section-C. All working, including rough work, should be done on the same sheet as the rest of the answer. The intended marks for questions or parts of questions are given in brackets [ ]. This paper Consists of 8 printed pages ____________________________________________________________________________________ PART I Answer all questions While answering questions in this Part, indicate briefly your working and reasoning, wherever required . Question 1. a) State the Boolean expression and draw the truth table for the propositional logic p q. [1] b) Verify the Boolean expression using truth table : A+A = A. [1] Also name the law stated above. c) Consider the statement if an odd number of input signals are 1 then output is 1 [1] otherwise 0 . Name the gate represented by the given statement and also draw its symbol using two inputs. d) Using the truth table prove that p q p q [1] e) Reduce the expression : F = A.B + A .B + A.B +A .B [1] 1
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