ISRO Computer Science (CSE) 2009 Question Paper & Solutions

Attempt the ISRO Computer Science (CSE) 2009 previous year paper in real CBT exam mode or practice mode with verified answers and explanations.

All ISRO Computer Science (CSE) papers

80 questions.

Question 1

The subnet mask for a particular network is 255.255.31.0. Which of the following pairs of IP addresses could belong to this network?

  • A. 172.57.88.62 and 172.56.87.23
  • B. 10.35.28.2 and 10.35.29.4
  • C. 191.203.31.87 and 191.234.31.88
  • D. 128.8.129.43 and 128.8.161.55

Answer: D. 128.8.129.43 and 128.8.161.55

Explanation: The mask 255.255.31.0 corresponds to binary 11111111.11111111.00011111.00000000. For two IPs to be on the same network, (IP AND Mask) must be identical. \nFor (d): \n129 (10000001) AND 31 (00011111) = 1. \n161 (10100001) AND 31 (00011111) = 1. \nBoth result in network 128.8.1.0.

Question 2

In networking, UTP stands for

  • A. Unshielded T-connector port
  • B. Unshielded twisted pair
  • C. Unshielded terminating pair
  • D. Unshielded transmission process

Answer: B. Unshielded twisted pair

Explanation: UTP stands for Unshielded Twisted Pair, a common type of cable used in telephone wiring and LANs.

Question 3

The address resolution protocol (ARP) is used for

  • A. Finding the IP address from the DNS
  • B. Finding the IP address of the default gateway
  • C. Finding the IP address that corresponds to a MAC address
  • D. Finding the MAC address that corresponds to an IP address

Answer: D. Finding the MAC address that corresponds to an IP address

Explanation: ARP resolves a known IP address to a physical MAC address.

Question 4

Which of the following is a MAC address?

  • A. 192.166.200.50
  • B. 00056A : 01A01A5CCA7FF60
  • C. 568, Airport Road
  • D. 01 : A5 : BB : A7 : FF : 60

Answer: D. 01 : A5 : BB : A7 : FF : 60

Explanation: A MAC address is a 48-bit address typically represented as 6 pairs of hexadecimal digits separated by colons.

Question 5

What is the primary purpose of a VLAN?

  • A. Demonstrating the proper layout for a network
  • B. Simulating a network
  • C. To create a virtual private network
  • D. Segmenting a network inside a switch or device

Answer: D. Segmenting a network inside a switch or device

Explanation: VLANs (Virtual Local Area Networks) are used to partition a physical network into logical segments.

Question 6

SHA-1 is a

  • A. encryption algorithm
  • B. decryption algorithm
  • C. key exchange algorithm
  • D. message digest function

Answer: D. message digest function

Explanation: SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function that produces a 160-bit hash value known as a message digest.

Question 7

Advanced Encryption Standard (AES) is based on

  • A. Asymmetric key algorithm
  • B. Symmetric key algorithm
  • C. Public key algorithm
  • D. Key exchange

Answer: B. Symmetric key algorithm

Explanation: AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data.

Question 8

The primary purpose of an operating system is

  • A. To make most efficient use of the computer hardware
  • B. To allow people to use the computer
  • C. To keep systems programmers employed
  • D. To make computers easier to use

Answer: A. To make most efficient use of the computer hardware

Explanation: The primary goal of an OS is to manage hardware resources efficiently, although convenience is also a major goal.

Question 9

Which is the correct definition of a valid process transition in an operating system?

  • A. Wake up : ready -> running
  • B. Dispatch : ready -> running
  • C. Block : ready -> running
  • D. Timer runout : -> ready -> running

Answer: B. Dispatch : ready -> running

Explanation: Dispatching is the transition of a process from the Ready state to the Running state. 'Wake up' is Blocked->Ready. 'Block' is Running->Blocked. 'Timer runout' is Running->Ready.

Question 10

The correct matching of the following pairs is: A. Disk check B. Batch processing C. Time sharing D. Stack operation vs 1. Round robin 2. Scan 3. LIFO 4. FIFO

  • A. A-3, B-4, C-2, D-1
  • B. A-4, B-3, C-2, D-1
  • C. A-3, B-4, C-1, D-2
  • D. A-2, B-4, C-1, D-3

Answer: D. A-2, B-4, C-1, D-3

Explanation: Disk Check -> SCAN algorithm. Batch processing -> FIFO (First In First Out). Time sharing -> Round Robin. Stack -> LIFO.

Question 11

A page fault

  • A. Occurs when a program accesses an available page on memory
  • B. is an error in a specific page
  • C. is a reference to a page belonging to another program
  • D. occurs when a program accesses a page not currently in memory

Answer: D. occurs when a program accesses a page not currently in memory

Explanation: A page fault is an exception that occurs when a program tries to access a block of memory that is not stored in the physical memory (RAM).

Question 12

Using a larger block size in a fixed block size file system leads to

  • A. better disk throughput but poorer disk space utilization
  • B. better disk throughput and better disk space utilization
  • C. poorer disk throughput but better disk space utilization
  • D. poorer disk throughput and poorer disk space utilization

Answer: A. better disk throughput but poorer disk space utilization

Explanation: Larger blocks reduce the number of I/O operations (overhead) improving throughput, but increase internal fragmentation (wastage) for small files.

Question 13

Which of the following statements about synchronous and asynchronous I/O is NOT true?

  • A. An ISR is invoked on completion of I/O in synchronous I/O but not in asynchronous I/O
  • B. In both synchronous and asynchronous I/O, an ISR is invoked after completion of the I/O
  • C. A process making a synchronous I/O call waits until I/O is complete
  • D. In the case of synchronous I/O, the process waiting for the completion of I/O is woken up by the ISR

Answer: B. In both synchronous and asynchronous I/O, an ISR is invoked after completion of the I/O

Explanation: This question phrasing is tricky. Usually, interrupts (and ISRs) are used in both to signal completion. However, in synchronous I/O, the process waits. In asynchronous, it doesn't. The option claiming ISR is invoked in both is actually TRUE physically. ISRO key suggests (b), likely implying there's a difference in how the user process perceives it, or referring to polling vs interrupt.

Question 14

Consider three CPU-intensive processes, which require 10, 20 and 30 time units and arrive at times 0, 2 and 6, respectively. How many context switches are needed if the operating system implements a shortest remaining time first scheduling algorithm? Do not count the context switches at time zero and at the end.

  • A. 1
  • B. 2
  • C. 3
  • D. 4

Answer: B. 2

Explanation: P1(10), P2(20), P3(30). Arrivals 0, 2, 6. \nT=0: P1 starts. \nT=2: P1 rem=8, P2=20. P1 continues. \nT=6: P1 rem=4, P2=20, P3=30. P1 continues. \nT=10: P1 ends. Switch to P2. (Context Switch 1). \nT=30: P2 ends. Switch to P3. (Context Switch 2). \nT=60: P3 ends. \nTotal switches = 2.

Question 15

The performance of Round Robin algorithm depends heavily on

  • A. size of the process
  • B. the I/O bursts of the process
  • C. the CPU bursts of the process
  • D. the size of the time quantum

Answer: D. the size of the time quantum

Explanation: If the time quantum is too large, it behaves like FCFS. If too small, context switch overhead dominates.

Question 16

Consider a system having "n" resources of same type. These resources are shared by 3 processes, A, B, C. These have peak demands of 3, 4, and 6 respectively. For what value of "n" deadlock won't occur

  • A. 15
  • B. 9
  • C. 10
  • D. 13

Answer: D. 13

Explanation: Deadlock condition: n < (3-1) + (4-1) + (6-1) + 1 = 11. If n >= 11, deadlock is impossible. 13 is a safe value.

Question 17

Consider a set of 5 processes... (P1, P2, P3, P4, P5 with Burst 10, 5, 3, 20, 2 and Priority 5, 2, 1, 4, 3). Lower number = Higher priority. Non-preemptive. Average waiting time?

  • A. 12.8 ms
  • B. 11.8 ms
  • C. 10.8 ms
  • D. 09.8 ms

Answer: C. 10.8 ms

Explanation: Execution Order: P2 (Arr 0, Prio 2 vs P1 Prio 5) -> P3 (Arr 2, Prio 1) -> P4 (Arr 5, Prio 4) -> P5 (Arr 10, Prio 3) -> P1 (Arr 0, Prio 5). \nTimeline: P2(0-5), P3(5-8), P4(8-28), P5(28-30), P1(30-40). \nWait times: P2=0, P3=5-2=3, P4=8-5=3, P5=28-10=18, P1=30-0=30. \nAvg = (0+3+3+18+30)/5 = 54/5 = 10.8 ms.

Question 18

The range of integers that can be represented by an n-bit 2's complement number system is

  • A. -2^(n-1) to (2^(n-1) - 1)
  • B. -(2^(n-1) - 1) to (2^(n-1) - 1)
  • C. -2^(n-1) to 2^(n-1)
  • D. -(2^(n-1) + 1) to (2^(n-1) - 1)

Answer: A. -2^(n-1) to (2^(n-1) - 1)

Explanation: Standard range for 2's complement. For n=8, -128 to 127.

Question 19

The switching expression corresponding to f(A, B, C, D) = Σ(1, 4, 5, 9, 11, 12) is

  • A. BC'D' + A'C'D + AB'D
  • B. ABC' + ACD + B'C'D
  • C. ACD' + A'BC' + AC'D'
  • D. A'BD + ACD' + BCD'

Answer: A. BC'D' + A'C'D + AB'D

Explanation: Simplification using K-Map yields BC'D' + A'C'D + AB'D.

Question 20

Consider the following boolean function of four variables f(w, x, y, z) = Σ(1, 3, 4, 6, 9, 11, 12, 14), the function is

  • A. Independent of one variable
  • B. Independent of two variables
  • C. Independent of three variables
  • D. Dependent on all variables

Answer: B. Independent of two variables

Explanation: The function simplifies to x XOR z (or x'z + xz'). It is independent of w and y.

Question 21

In which addressing mode, the effective address of the operand is generated by adding a constant value to the content of a register?

  • A. Absolute mode
  • B. Indirect mode
  • C. Immediate mode
  • D. Index mode

Answer: D. Index mode

Explanation: Index addressing mode calculates EA = Base + Displacement (Index).

Question 22

A certain microprocessor requires 4.5 microseconds to respond to an interrupt. Assuming that the three interrupts I1, I2 and I3 require the following execution time after the interrupt is recognized: 25, 35, 20us. I1 has highest priority, I3 lowest. What is the possible range of time for I3 to be executed?

  • A. 24.5 microseconds to 39.5 microseconds
  • B. 24.5 microseconds to 93.5 microseconds
  • C. 4.5 microseconds to 24.5 microseconds
  • D. 29.5 microseconds 93.5 microseconds

Answer: B. 24.5 microseconds to 93.5 microseconds

Explanation: Min time (no other interrupts): 4.5 (response) + 20 (exec) = 24.5. Max time (I1 and I2 occur): 4.5 + 25 (I1) + 4.5 + 35 (I2) + 4.5 + 20 (I3) = 93.5.

Question 23

The process of organizing the memory into two banks to allow 8 and 16 bit data operation is called

  • A. Bank switching
  • B. Indexed mapping
  • C. Two-way memory interleaving
  • D. Memory segmentation

Answer: C. Two-way memory interleaving

Explanation: Interleaving allows simultaneous access to adjacent memory locations (banks), supporting different data widths efficiently.

Question 24

Suppose the numbers 7, 5, 1, 8, 3, 6, 0, 9, 4, 2 are inserted in that order into an initially empty binary search tree. What is the in-order traversal sequence of the resultant tree?

  • A. 7 5 1 0 3 2 4 6 8 9
  • B. 0 2 4 3 1 6 5 9 8 7
  • C. 0 1 2 3 4 5 6 7 8 9
  • D. 9 8 6 4 2 3 0 1 5 7

Answer: C. 0 1 2 3 4 5 6 7 8 9

Explanation: The in-order traversal of a binary search tree always yields the sorted sequence of the inserted elements.

Question 25

A data structure is required for storing a set of integers such that operations 'deletion of smallest' and 'insertion' can be done in log n time. Which data structure is best?

  • A. A heap can be used but not a balanced binary search tree
  • B. A balanced binary search tree can be used but not a heap
  • C. Both balanced binary search tree and heap can be used
  • D. Neither balanced search tree nor heap can be used

Answer: B. A balanced binary search tree can be used but not a heap

Explanation: Heaps support efficient find-min/delete-min but checking 'if element is not already present' (search) is O(n). Balanced BSTs support search, insert, and delete-min all in O(log n).

Question 26

The following numbers are inserted into an empty binary search tree in the given order: 10, 1, 3, 5, 15, 12, 16. What is the height of the binary search tree?

  • A. 2
  • B. 3
  • C. 4
  • D. 6

Answer: B. 3

Explanation: Tree: 10 -> (L: 1 -> R: 3 -> R: 5) and (R: 15 -> L: 12, R: 16). Path 10-1-3-5 has 3 edges. Height = 3.

Question 27

Assume that the operators +, -, x are left associative and ^ is right associative. The postfix expression corresponding to a + b x c - d ^ e ^ f is

  • A. abc x + def ^ ^ -
  • B. abc x + de ^ f ^ -
  • C. ab + c x d - e ^ f ^
  • D. - + a x bc ^ ^ def -

Answer: A. abc x + def ^ ^ -

Explanation: Precedence: ^ > x > +,-. Right assoc of ^ means d^e^f is d^(e^f). Steps: a + (b*c) - (d^(e^f)) -> abc*+ def^^ -.

Question 28

The infix expression A + (B - C)*D is correctly represented in prefix notation as

  • A. A + B - C * D
  • B. + A * - B C D
  • C. A B C - D * +
  • D. A + BC - D *

Answer: B. + A * - B C D

Explanation: A + ((B-C)*D) -> A + (* - B C D) -> + A * - B C D.

Question 29

A one dimensional array A has indices 1 ... 75. Each element is a string and takes up three memory words. The array is stored location 1120 decimal. The starting address of A[49] is

  • A. 1267
  • B. 1164
  • C. 1264
  • D. 1169

Answer: C. 1264

Explanation: Addr(A[i]) = Base + (i - Lower) * Size. Addr = 1120 + (49 - 1) * 3 = 1120 + 144 = 1264.

Question 30

The five items: A, B, C, D, and E are pushed in a stack... popped four times... inserted in queue... two deleted from queue... pushed back on stack... one popped. The popped item is

  • A. A
  • B. B
  • C. C
  • D. D

Answer: D. D

Explanation: Stack: [ABCDE]. Pop 4: E,D,C,B. Queue: E,D,C,B. Delete 2: E, D. Stack: [A, E, D]. Pop 1: D.

Question 31

A full binary tree with n leaves contains

  • A. n nodes
  • B. log2 n nodes
  • C. 2n - 1
  • D. 2^n nodes

Answer: C. 2n - 1

Explanation: In a full binary tree (where every node has 0 or 2 children), if there are L leaves, the total number of nodes N = 2L - 1.

Question 32

The expression 1 * 2 ^ 3 * 4 ^ 5 * 6 will be evaluated as

  • A. 32^30
  • B. 162^30
  • C. 49152
  • D. 173458

Answer: C. 49152

Explanation: Precedence: ^ > *. 2^3 = 8. 4^5 = 1024. Expression: 1 * 8 * 1024 * 6 = 49152.

Question 33

The feature in object-oriented programming that allows the same operation to be carried out differently, depending on the object, is

  • A. Inheritance
  • B. Polymorphism
  • C. Over functioning
  • D. Overriding

Answer: B. Polymorphism

Explanation: Polymorphism allows objects of different classes to respond to the same method call in their own way.

Question 34

The microinstructions stored in the control memory of a processor have a width of 26 bits... micro op 13 bits... X field... Y field... 8 status bits... size of control memory?

  • A. 10, 3, 1024
  • B. 8, 5, 256
  • C. 5, 8, 2048
  • D. 10, 3, 512

Answer: A. 10, 3, 1024

Explanation: Total 26 bits. Op 13. Status bits 8 -> MUX select Y needs 3 bits. Next addr X = 26-13-3=10 bits. Address space 2^10 = 1024 words.

Question 35

A CPU has 24-bit instructions. A program starts at address 300 (in decimal). Which of the following is a legal program counter (all values in decimal)?

  • A. 400
  • B. 500
  • C. 600
  • D. 700

Answer: C. 600

Explanation: Instructions are 24 bits = 3 bytes long. PC addresses must be multiples of 3 relative to start (300). 600-300=300 (divisible by 3). 400, 500, 700 are not.

Question 36

Consider a disk pack with 16 surfaces, 128 tracks per surface and 256 sectors per track. 512 bytes of data... Capacity and bits for address?

  • A. 256 Mbyte, 19 bits
  • B. 256 Mbyte, 28 bits
  • C. 512 Mbyte, 20 bits
  • D. 64 Gbyte, 28 bits

Answer: A. 256 Mbyte, 19 bits

Explanation: Capacity = 16 * 128 * 256 * 512 = 256 MB. Address bits = log2(16)+log2(128)+log2(256) = 4+7+8 = 19 bits.

Question 37

Consider a pipelined processor with the following four stages... Operand forwarding is used... Number of clock cycles for 3 instructions (ADD, MUL, SUB)?

  • A. 7
  • B. 8
  • C. 10
  • D. 14

Answer: B. 8

Explanation: With operand forwarding, stalls are minimized. ADD (1 cycle exec), MUL (3 cycles exec), SUB (1 cycle). MUL depends on ADD (no stall with forwarding). SUB depends on MUL (stall until MUL finishes). Timeline analysis yields 8 cycles.

Question 38

The use of multiple register windows with overlap causes a reduction in the number of memory accesses for

  • A. Function locals and parameters
  • B. Register saves and restores
  • C. Instruction fetches
  • D. 1 only
  • E. 2 only
  • F. 3 only
  • G. 1, 2 and 3

Answer: D. 1 only

Explanation: Register windows reduce memory traffic for passing parameters and saving local variables during function calls. (Question format in image slightly confusing, answer is 1).

Question 39

A processor that has carry, overflow and sign flag bits... addition of 01001101 and 11101001... status of flags?

  • A. 1, 1, 0
  • B. 1, 0, 0
  • C. 0, 1, 0
  • D. 1, 0, 1

Answer: B. 1, 0, 0

Explanation: 77 + (-23) = 54. 01001101 + 11101001 = 1 00110110. Carry=1. Sign=0. Overflow=0 (Pos+Neg never overflows).

Question 40

The two numbers given below are multiplied using the Booth's algorithm... How many additions/subtractions are required?

  • A. 6
  • B. 8
  • C. 10
  • D. 12

Answer: B. 8

Explanation: Counting transitions in the multiplier (0111011110111101) including implicit LSB 0. There are 8 transitions (0-1 or 1-0).

Question 41

The addition of 4-bit, two's complement, binary numbers 1101 and 0100 results in

  • A. 0001 and an overflow
  • B. 1001 and no overflow
  • C. 0001 and no overflow
  • D. 1001 and an overflow

Answer: C. 0001 and no overflow

Explanation: (-3) + (4) = 1. 1101 + 0100 = (1)0001. Result is 1. No overflow (signs different).

Question 42

Which of the following statements about relative addressing mode is FALSE?

  • A. It enables reduced instruction size
  • B. It allows indexing of array element with same instruction
  • C. It enables easy relocation of data
  • D. It enables faster address calculation than absolute addressing

Answer: D. It enables faster address calculation than absolute addressing

Explanation: Relative addressing requires an addition (PC + Offset), whereas absolute addressing requires no calculation (Address is in instruction).

Question 43

Substitution of values for names (whose values are constants) is done in

  • A. Local optimization
  • B. Loop optimization
  • C. Constant folding
  • D. Strength reduction

Answer: C. Constant folding

Explanation: Constant folding is the process of recognizing and evaluating constant expressions at compile time.

Question 44

A root alpha of equation f(x) = 0 can be computed to any degree of accuracy if a 'good' initial approximation x0 is chosen for which

  • A. f(x0) > 0
  • B. f(x0) f''(x0) > 0
  • C. f(x0) f''(x0) < 0
  • D. f''(x0) > 0

Answer: B. f(x0) f''(x0) > 0

Explanation: Convergence of Newton-Raphson is guaranteed if f(x0) * f''(x0) > 0.

Question 45

Which of the following statement is correct (Difference operator)

  • A. Delta(uk vk) = uk Delta vk + vk Delta uk
  • B. Delta(uk vk) = vk+1 Delta uk + uk Delta vk
  • C. Delta(uk vk) = vk+1 Delta uk + uk+1 Delta vk
  • D. Delta(uk vk) = uk+1 Delta vk + vk Delta uk

Answer: B. Delta(uk vk) = vk+1 Delta uk + uk Delta vk

Explanation: The product rule for finite differences is Delta(uv) = u Delta v + v(k+1) Delta u. (Or equivalent forms).

Question 46

The shift operator E is defined as E[f(xi)] = f(xi + h) and E^-1[f(xi)] = f(xi - h). Then Delta (forward difference) in terms of E is

  • A. E - 1
  • B. E
  • C. 1 - E^-1
  • D. 1 - E

Answer: A. E - 1

Explanation: Delta f(x) = f(x+h) - f(x) = E f(x) - f(x) = (E-1) f(x).

Question 47

The formula int y dx approx h/12 (...) is called

  • A. Simpson rule
  • B. Trapezoidal rule
  • C. Romberg's rule
  • D. Gregory's formula

Answer: D. Gregory's formula

Explanation: The formula involving correction terms with deltas/nablas is Gregory's integration formula.

Question 48

The cubic polynomial y(x) which takes the following values: y(0)=1, y(1)=0, y(2)=1 and y(3)=10 is

  • A. x³ + 2x^2 + 1
  • B. x³ + 3x^2 - 1
  • C. x³ + 1
  • D. x³ - 2x^2 + 1

Answer: D. x³ - 2x^2 + 1

Explanation: Testing options: At x=1, y=0. (d) 1 - 2 + 1 = 0. Matches.

Question 49

x = a cos(t), y = b sin(t) is the parametric form of

  • A. Ellipse
  • B. Hyperbola
  • C. Circle
  • D. Parabola

Answer: A. Ellipse

Explanation: (x/a)^2 + (y/b)^2 = cos² t + sin² t = 1. Equation of an ellipse.

Question 50

The value of x at which y is minimum for y = x² - 3x + 1 is

  • A. -3/2
  • B. 3/2
  • C. 0
  • D. -5/4

Answer: B. 3/2

Explanation: dy/dx = 2x - 3 = 0 => x = 1.5 (3/2).

Question 51

The formula Pk = ... is

  • A. Newton's backward formula
  • B. Gauss forward formula
  • C. Gauss backward formula
  • D. Stirling's formula

Answer: A. Newton's backward formula

Explanation: Standard ISRO key indicates Newton's backward formula.

Question 52

If G is a graph with e edges and n vertices the sum of the degrees of all vertices in G is

  • A. e
  • B. e/2
  • C. e²
  • D. 2 e

Answer: D. 2 e

Explanation: Handshaking lemma: Sum of degrees = 2 * number of edges.

Question 53

Let G be an arbitrary graph with n nodes and k components. If a vertex is removed from G, the number of components in the resultant graph must necessarily lie down between

  • A. k and n
  • B. k - 1 and k + 1
  • C. k - 1 and n
  • D. k + 1 and n - k

Answer: C. k - 1 and n

Explanation: Removing a vertex can reduce components by 1 (if isolated) or increase them (if cut vertex). Max components is n-1.

Question 54

A graph in which all nodes are of equal degree is known as

  • A. Multigraph
  • B. Non regular graph
  • C. Regular graph
  • D. Complete graph

Answer: C. Regular graph

Explanation: In a k-regular graph, every vertex has degree k.

Question 55

In a graph G there is one and only one path between every pair of vertices then G is a

  • A. Path
  • B. Walk
  • C. Tree
  • D. Circuit

Answer: C. Tree

Explanation: A tree is a connected graph with no cycles, ensuring a unique path between any two nodes.

Question 56

A simple graph (a graph without parallel edge or loops) with n vertices and k components can have at most

  • A. n edges
  • B. n - k edges
  • C. (n - k)(n - k + 1)
  • D. (n - k)(n - k + 1)/2 edges

Answer: D. (n - k)(n - k + 1)/2 edges

Explanation: Max edges occur when one component is a complete graph of n-k+1 vertices and rest are isolated.

Question 57

Consider the polynomial p(x) = a0 + a1x + a2x^2 + a3x^3, where ai != 0. The minimum number of multiplications needed to evaluate p on an input x is

  • A. 3
  • B. 4
  • C. 6
  • D. 9

Answer: A. 3

Explanation: Using Horner's method: a0 + x(a1 + x(a2 + x(a3))). 3 multiplications.

Question 58

Consider the following code written in a pass-by-reference language... subroutine swap(ix, iy)... call swap(ia, ib+5)... print ia, ib

  • A. 13, 8
  • B. 8, 3
  • C. 13, 3
  • D. 8, 13

Answer: A. 13, 8

Explanation: With pass-by-reference, the expression 'ib+5' evaluates to 8 (temp location). Swap exchanges ia (3) and temp (8). ia becomes 8? Wait. \nia=3, ib=8. Call swap(ia, 13). ix refers to ia, iy refers to temp(13). \nSwap: ia becomes 13, temp becomes 3. \nResult: ia=13, ib=8. (ib is not changed). Output 13, 8.

Question 59

A square matrix A is called orthogonal if A'A =

  • A. I
  • B. A
  • C. -A
  • D. -I

Answer: A. I

Explanation: Definition of orthogonal matrix.

Question 60

If two adjacent rows of a determinant are interchanged, the value of the determinant

  • A. becomes zero
  • B. remains unaltered
  • C. becomes infinite
  • D. becomes negative of its original value

Answer: D. becomes negative of its original value

Explanation: Property of determinants.

Question 61

If determinant of [[3, 3], [x, 5]] = 3, the value of x is

  • A. 2
  • B. 3
  • C. 4
  • D. 5

Answer: C. 4

Explanation: 15 - 3x = 3 => 3x = 12 => x = 4.

Question 62

If A, B, C are any three matrices, then A' + B' + C' is equal to

  • A. a null matrix
  • B. A + B + C
  • C. (A + B + C)'
  • D. -(A + B + C)

Answer: C. (A + B + C)'

Explanation: Transpose of sum is sum of transposes.

Question 63

Determinant of [[265, 240, 219], [240, 225, 198], [219, 198, 181]] =

  • A. 779
  • B. 679
  • C. 0
  • D. 256

Answer: C. 0

Explanation: The rows are linearly dependent (or differences are consistent), resulting in zero determinant.

Question 64

Let f(x) be the continuous probability density function of a random variable x, the probability that a < x <= b is

  • A. f(b-a)
  • B. f(b) - f(a)
  • C. integral from a to b of f(x)dx
  • D. integral from a to b of xf(x)dx

Answer: C. integral from a to b of f(x)dx

Explanation: Probability is the area under the PDF curve.

Question 65

If the mean of a normal frequency distribution of 1000 items is 25 and its standard deviation is 2.5, then its maximum ordinate is

  • A. 1000 e^-25 / $\sqrt{2pi}$
  • B. 1000 / $\sqrt{2pi}$
  • C. 1000 e^-2.5 / $\sqrt{2pi}$
  • D. 400 / $\sqrt{2pi}$

Answer: D. 400 / $\sqrt{2pi}$

Explanation: Max ordinate is at mean. Value = N / (sigma * $\sqrt{2pi}$). 1000 / (2.5 * $\sqrt{2pi}$) = 400 / $\sqrt{2pi}$.

Question 66

If the pdf of a Poisson distribution is given by f(x) = e^-2 2^x / x! then its mean is

  • A. 2^x
  • B. 2
  • C. -2
  • D. 1

Answer: B. 2

Explanation: For Poisson, mean = lambda. Here lambda = 2.

Question 67

Activities which ensure that the software that has been build, is traceable to customer requirement is covered as part of

  • A. Verification
  • B. Validation
  • C. Maintenance
  • D. Modeling

Answer: B. Validation

Explanation: Validation ensures 'Are we building the right product?' (Customer requirements).

Question 68

A testing method which is normally used as the acceptance test for a software system, is

  • A. Regression Testing
  • B. Validation
  • C. Unit Testing
  • D. System Testing

Answer: B. Validation

Explanation: Acceptance testing is a form of Validation (often called Beta testing or UAT). Note: ISRO key sometimes points to 'Regression' or 'System', but Validation is the best fit.

Question 69

The 'command' used to change contents of one database using the contents of another database by linking them on a common key field?

  • A. Replace
  • B. Join
  • C. Change
  • D. Update

Answer: D. Update

Explanation: SQL UPDATE command with JOIN logic.

Question 70

A locked database file can be

  • A. Accessed by only one user
  • B. Modified by users with the correct password
  • C. Used to hide sensitive information
  • D. Updated by more than one user

Answer: A. Accessed by only one user

Explanation: Locking prevents concurrent access to maintain consistency.

Question 71

Which of the following contains complete record of all activity that affected the contents of a database during a certain period of time?

  • A. Transaction log
  • B. Query language
  • C. Report writer
  • D. Data manipulation language

Answer: A. Transaction log

Explanation: The log records all modifications for recovery purposes.

Question 72

Purpose of 'Foreign Key' in a table is to ensure

  • A. Null Integrity
  • B. Referential Integrity
  • C. Domain Integrity
  • D. Null and Domain Integrity

Answer: B. Referential Integrity

Explanation: Foreign keys ensure that relationships between tables remain consistent.

Question 73

Which of the following scenarios may lead to an irrecoverable error in a database system?

  • A. A transaction writes a data item after it is read by an uncommitted transaction
  • B. A transaction reads a data item after it is read by an uncommitted transaction
  • C. A transaction reads a data item after it is written by an committed transaction
  • D. A transaction reads a data item after it is written by an uncommitted transaction

Answer: D. A transaction reads a data item after it is written by an uncommitted transaction

Explanation: This is a dirty read. If the uncommitted transaction aborts, the reading transaction has invalid data and might have committed, making it irrecoverable.

Question 74

Use of IPSEC in tunnel mode results in

  • A. IP packet with same header
  • B. IP packet with new header
  • C. IP packet without header
  • D. No changes in IP packet

Answer: B. IP packet with new header

Explanation: Tunnel mode encapsulates the entire original IP packet and adds a new IP header.

Question 75

Special software to create a job queue is called a

  • A. Driver
  • B. Spooler
  • C. Interpreter
  • D. Linkage editor

Answer: B. Spooler

Explanation: Spooling (Simultaneous Peripheral Operations On-Line) buffers jobs (like print jobs) in a queue.

Question 76

Process is

  • A. A program in high level language kept on disk
  • B. Contents of main memory
  • C. A program in execution
  • D. A job in secondary memory

Answer: C. A program in execution

Explanation: Standard definition of a process.

Question 77

When a process is rolled back as a result of deadlock the difficulty which arises is

  • A. Starvation
  • B. System throughput
  • C. Low device utilization
  • D. Cycle stealing

Answer: A. Starvation

Explanation: If the same process is always picked for rollback, it may never complete (starvation).

Question 78

On receiving an interrupt from an I/O device, the CPU

  • A. Halts for a predetermined time
  • B. Branches off to the interrupt service routine after completion of the current instruction
  • C. Branches off to the interrupt service routine immediately
  • D. Hands over control of address bus and data bus to the interrupting device

Answer: B. Branches off to the interrupt service routine after completion of the current instruction

Explanation: The CPU completes the current instruction cycle before acknowledging the interrupt and branching.

Question 79

Compared to CISC processors, RISC processors contain

  • A. More register and smaller instruction set
  • B. larger instruction set and less registers
  • C. less registers and smaller instruction set
  • D. more transistor elements

Answer: A. More register and smaller instruction set

Explanation: RISC architectures use simple instructions and a large register file.

Question 80

Which of the following is/are true of the auto-increment addressing mode? 1. It is useful in creating self-relocating code 2. If it is included in an Instruction set architecture, then an additional ALU is required for effective calculations 3. The amount of increment depends on the size of the data item accessed

  • A. 1 only
  • B. 2 only
  • C. 3 only
  • D. 2 and 3 only

Answer: C. 3 only

Explanation: Auto-increment advances the pointer by the size of the data element accessed (e.g., 2 for word, 4 for double).