1. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either (A) A NAND or an EX-OR (B) An OR or an EX-NOR (C) An AND or an EX-OR (D) A NOR or an EX-NOR (Ans) Hints and Solution : The output of a logic gate is 1 when all inputs are at logic 0. The gate is either a NOR or an EX- NOR. Input Output A B Y 0 0 1 0 1 0 1 0 0 1 1 0 Truth Table for NOR Gate Input Output A B Y 0 0 1 0 1 0 1 0 0 1 1 1 Truth Table for EX-NOR Gate 2. What is the simplification of the following Boolean expression in a Product-Of-Sum form? (A) Out = (A+B+ NOT(C)) (A+NOT(C)+ D) (C+NOT(D)) (B) Out = (A+B) (A+NOT(D)) (B+NOT(C)+D) (C) Out = (B+C+ NOT(D)) (A+C+ NOT(D)) ( NOT(C)+D) (Ans) (D) Out = (A+NOT(B)+D) (C+D) (B+NOT(C)+D) Hints and Solution : Transfer the seven maxterms to the map below as 0s. Map the 0s as they appear left to right top to bottom on the map above. Now form groups of cells. The final result is product of the three sums i.e. Out = (B+C+ NOT(D)) (A+C+ NOT(D)) ( NOT(C)+D) 3. What is the appropriate form for the given k-map? (A) F(W,X,Y,Z) = Σm (0,3,4,6,8,10,11,12,14) (B) F(W,X,Y,Z) = Σm (0,2,5,6,8,10,13,14,15) (Ans) (C) F(W,X,Y,Z) = Σm (1,2,5,6,8,9,11,14,15) (D) F(W,X,Y,Z) = Σm (1,2,3,7,9,10,11,14,15) F(W,X,Y,Z) = Σm (0,2,5,6,8,10,13,14,15) 4. How many fibres are required by a unidirectional and bidirectional ring respectively,to support their working traffic? (A) 1 and 1 (B) 2 and 1 (C) 2 and 2 (D) 1 and 2 (Ans) Hints and Solution : SONET rings can be classified by the routing principle and the SONET overhead used for triggering protection switching. A ring is called a unidirectional ring if bidirectional working signals follow opposite physical routes around a ring , while bidirectional working signals in a bidirectional ring follow the same route. Due to this routing principle, a unidirectional and a bidirectional ring, require one and two fibers respectively, to support their working traffic. 5. Find odd one out related to transmission media cables? (A) Basic rate ISDN can transmit data at a rate of 512 kilobits per second on an existing local telephone line. (Ans) (B) A T1 line is a dedicated telephone connection of 24 channels. (C) A T1 channel can be configured to carry either voice or data traffic. (D) Cable modems provide high-speed transmission over cable TV lines and are shared by many users. Hints and Solution : Each ISDN line is made up of separate 64-Kbps "channels" for sending and receiving calls, plus a channel that is used primarily for signaling. 6. Mechanism to protect private networks from outside attack is (A) Firewall (Ans) (B) Antivirus (C) Digital signature (D) Formatting Hints and Solution : Firewall is the mechanism to protect private networks from outside attack. It is a software or hardware used to isolate a private network from a public network. 7. What does a metric of 16 hops represent when using RIP? (A) Number of hops to the destination (B) Destination unreachable (Ans) (C) Number of routers (D) Bandwidth Hints and Solution : Routing Information Protocol is a distance vector routing protocol that uses hop count as its metric. The maximum hop count is 15. 16 hops are considered unreachable. RIP updates are broadcast every 30 seconds by default. RIP has an administrative distance of 120. 8. If the 8085 adds 87H and 79H, specify the contents of the accumulator and the status of the S, Z, and CY flag? (A) 10H; S =1, Z = 0, CY = 1 (B) 01H; S =0, Z = 0, CY = 1 (C) 00H; S =0, Z = 1, CY = 1 (Ans) (D) 11H; S =1, Z = 1, CY = 0 Hints and Solution : The sum of 87H and 79H =100H. Therefore, the accumulator will have 00H, and the flags will be S =0, Z = 1, CY = 1 9. If the stack pointer is initialized with (4FEB) H, then after execution of Push operation in 8085 microprocessor, the Stack Pointer shall be (A) 4FEA (B) 4FEC (C) 4FE9 (D) 4FED (Ans) Hints and Solution : If the stack pointer is initialized with (4FEB) H, then after execution of push operation in 8085 microprocessor, stack pointer shall be 4FED. 10. If an input and output port can have the same 8-bit address how does the 8085 differentiate between the ports? (A) The input port requires the WR and the output port requires the RD signal (B) The input port requires the RD and the output port requires the WR signal (Ans) (C) The input port and output port requires low I/O (D) None of the above Hints and Solution : The 8085 differentiates between the input and output ports of the same address by the control signal. The input port requires the RD and the output port requires the WR signal. 11. Consider the grammar given below E → E+E | E*E | E-E | E/E | E^E | (E) | id Assume that + and – have the same but least precedence, * and / have the next higher precedence but the same precedence and finally ^ has the highest precedence. Assume + and – associate to the left like * and / and that ^ associates to the right. Choose the correct statement with respect to relations for the ordered pairs (^,^) , (-,-) , (+,+) , (*,*) in the operator precedence table constructed for the grammar (A) all < (B) all > (C) <,>,=,< (D) <,>,>,> (Ans) Hints and Solution : Relations for the ordered pairs (^,^),(-,-) , (+,+), (*,*) in the operator precedence table constructed for the grammar will be <,>,>,> as exponent is of right associative to itself and + , – , * and / are left associative 12. P, Q, R are three languages. If P and R are regular and if PQ=R, then (A) Q has to be regular (B) Q cannot be regular (C) Q need not be regular (Ans) (D) Q has to be a CFL Hints and Solution : Proof as follows: 1. Let P=Q=R=EMPTY SET. The equation is satisfied. So this rules out (B). 2. Let P=R be Σ* then any Q will satisfy the equation. The demands of (A) & (D) are invalid. 3. So the answer is (C). 13. Which of the following conversion is not possible (algorithmically)? (A) regular grammar to context-free grammar (B) nondeterministic FSA to deterministic FSA (C) nondeterministic PDA to deterministic PDA (Ans) (D) nondeterministic TM to deterministic TM Hints and Solution : It is not possible to convert nondeterministic PDA to deterministic PDA 14. The following are the set of processes with their respective CPU burst time (in milliseconds). Processes CPU Burst time P1 10 P2 5 P3 5 What will be the average waiting time if the process arrived in the order: P1, P2 & P3? (A) 6.82 unit (B) 7.56 unit (C) 8.33 unit (Ans) (D) 9.97 unit Hints and Solution : CPU burst time indicates the time for which the process needs the CPU. Considering FCFS scheduling Processes CPU Burst time P1 10 P2 5 P3 5 For processes arriving in the order: P1 , P2 , P3 The Gantt Chart for the schedule is:. P1 P2 P3 0 10 5 20 Waiting time for P1 = 0; P2 = 10; P3 = 15 Average waiting time: (0 + 10 + 15)/3 = 8.33 unit of time 15. Match the following: Column I Column II p) time sharing (1) Program first executed when a computer is turned on q) process (2) Part of an operating system that communicates with the user r) bootstrap (3) Technique that allows multiprocessing on a computer with a single CPU s) shell (4) Activity of executing a program (p) (q) (r) (s) (A) (4), (1), (2), (3) (B) (3), (4), (1), (2) (Ans) (C) (2), (3), (4), (1) (D) (1), (4), (2), (3) Hints and Solution : p) time sharing-Technique that allows multiprocessing on a computer with a single CPU q) process-Activity of executing a program r) bootstrap-Program first executed when a computer is turned on s) shell-Part of an operating system that communicates with the user 16. In Priority Scheduling a priority number is associated with each process. The CPU is allocated to the process with the highest priority. The problem of starvation is resolved by which of the following? (A) Terminating the process. (B) Aging (Ans) (C) Mutual Exclusion (D) Semaphore Hints and Solution : Aging resolves or avoids the problem of starvation.