IAE Academy

PAPERS · ISRO

ISRO Scientist/Engineer Computer Science 2023 question paper

All 95 questions of ISRO's written test for Scientist/Engineer 'SC' (Computer Science), held on 7 January 2024, with ISRO's answer key. ISRO excluded Q.4, Q.5, Q.12, Q.23, Q.28 and Q.46 from evaluation.

Answers from ISRO's revised and final answer key of 16 February 2024.

questions · 100 marks
95questions · 100 marks
Part A: Computer Science
80Part A: Computer Science
Part B: aptitude
15Part B: aptitude

How the paper is marked

  • Part A (Q.1 to Q.80): 1 mark for a correct answer, minus 1/3 for a wrong answer.
  • Part B (Q.81 to Q.95): 1 or 2 marks as printed with each question, 20 marks in all, no negative marking.

Source: ISRO's recruitment advertisement ISRO:ICRB:02(EMC):2023 of 25 May 2023, item 16(b).

ISRO CS 2023 answer key

ISRO's answer key for ISRO Scientist/Engineer Computer Science 2023
QuestionPartMarksAnswer
Q.1A1B
Q.2A1B
Q.3A1A or B
Q.4A1Excluded
Q.5A1Excluded
Q.6A1A
Q.7A1A
Q.8A1C
Q.9A1C
Q.10A1D
Q.11A1B
Q.12A1Excluded
Q.13A1D
Q.14A1C
Q.15A1A
Q.16A1C
Q.17A1A
Q.18A1B
Q.19A1B
Q.20A1B
Q.21A1B
Q.22A1C
Q.23A1Excluded
Q.24A1C
Q.25A1B
Q.26A1D
Q.27A1A
Q.28A1Excluded
Q.29A1A
Q.30A1A
Q.31A1B
Q.32A1C
Q.33A1D
Q.34A1A
Q.35A1A
Q.36A1A
Q.37A1C
Q.38A1D
Q.39A1D
Q.40A1D
Q.41A1C
Q.42A1D
Q.43A1C
Q.44A1A
Q.45A1D
Q.46A1Excluded
Q.47A1C or D
Q.48A1A
Q.49A1C
Q.50A1C
Q.51A1D
Q.52A1B
Q.53A1C
Q.54A1A
Q.55A1A
Q.56A1B
Q.57A1A
Q.58A1D
Q.59A1B
Q.60A1B
Q.61A1C
Q.62A1D
Q.63A1A or B
Q.64A1C
Q.65A1B
Q.66A1A
Q.67A1B
Q.68A1C
Q.69A1A
Q.70A1B
Q.71A1A
Q.72A1A
Q.73A1A
Q.74A1D
Q.75A1C
Q.76A1C
Q.77A1C
Q.78A1B
Q.79A1B or C
Q.80A1A
Q.81B1D
Q.82B1D
Q.83B2B
Q.84B1A
Q.85B1A
Q.86B2A
Q.87B1A
Q.88B1C
Q.89B2C
Q.90B1C
Q.91B1D
Q.92B2D
Q.93B1A
Q.94B1C
Q.95B2A

ISRO excluded Q.4, Q.5, Q.12, Q.23, Q.28 and Q.46 from evaluation.

Part A: Computer Science Q.1 to Q.80

  1. Q.11 markOfficial answer: B
    ISRO CS 2023 question 1: 2Find the minimum spanning distance and the corresponding number of edges for the following graph (a) 10, 3 (b) 11, 4 (c) 15, 4 (d) 28, 7Tap to open full size

    Data Structures and Algorithms › Graph algorithms

    A minimum spanning tree of a connected graph with vertices always has edges. Kruskal's algorithm builds one by taking the lightest edges that do not form a cycle.

    Full solution
  2. Q.21 markOfficial answer: B
    ISRO CS 2023 question 2: 2Match the following : (A) Floyd Warshall (i) shortest path between two vertices (B) Dijkstra (ii) single source shortest path (C) Kruskal’s (iii) Minimum spanning tree (D)…Tap to open full size

    Data Structures and Algorithms › Graph algorithms

    Match each algorithm to its defining problem: Floyd-Warshall solves all pair shortest paths, Kruskal's builds a minimum spanning tree, and Dijkstra and Bellman-Ford are single-source methods. Fix the two unambiguous matches first and use them to eliminate options.

    Full solution
  3. Q.31 markOfficial answer: A or B
    ISRO CS 2023 question 3: 2Time complexity to find the diameter of a binary tree having n nodes is (a) O(n2) (b) O(n) (c) O(1) (d) O(log n)Tap to open full size

    Earlier, ISRO's key gave A.

    Data Structures and Algorithms › Trees & heaps

    Compute subtree heights and the best path through each node in a single post-order traversal, so each node is handled once in constant time.

    Full solution
  4. Q.41 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 4: 2The preorder traversal of a binary search tree is (10, 5, 1, 7, 40, 50). The postorder traversal is (a) (1, 5, 7, 10, 40, 50) (b) (50, 40, 10, 7, 5, 1) (c) (1, 7, 5, 10…Tap to open full size

    Earlier, ISRO's key gave B.

  5. Q.51 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 5Tap to open full size

    Earlier, ISRO's key gave B.

  6. Q.61 markOfficial answer: A
    ISRO CS 2023 question 6: 2Maximum number of Simple graphs possible with n vertices (a) 2n(n–1)/2 (b) 2(n–1)/2 (c) 2(n(n+1)/2) (d) 2n(n+1)Tap to open full size

    Probability and Statistics › Counting & axioms

    A simple graph on labelled vertices is fixed by choosing, for each of the vertex pairs, whether the edge is present, giving graphs.

    Full solution
  7. Q.71 markOfficial answer: A
    ISRO CS 2023 question 7Tap to open full size

    Compiler Design › Lexical analysis

    Read an NFA as a regular expression piece by piece. An alternation is two parallel branches joined by -edges. An -edge from the join back to an earlier final state is a Kleene star. The edge before that state is a prefix that appears only once.

    Full solution
  8. Q.81 markOfficial answer: C
    ISRO CS 2023 question 8Tap to open full size

    Theory of Computation › CFG & PDA

    Count parse trees by choosing the root production, which fixes which operator is applied last. Then count the trees of the two sub-strings. With no precedence in the grammar, each operator can be the root.

    Full solution
  9. Q.91 markOfficial answer: C
    ISRO CS 2023 question 9: 2Which of the following heap memory allocation strategies is likely to exploit spatial locality of memory accesses in a program, the most?Tap to open full size

    Operating Systems › Memory management

    Next Fit continues searching from the point of the last allocation, so consecutive requests are placed in adjacent memory. Data allocated together sits together, which is spatial locality.

    Full solution
  10. Q.101 markOfficial answer: D
    ISRO CS 2023 question 10: 2Which sequence below best describes the order in which the phases of a compiler typically work?Tap to open full size

    Compiler Design › Lexical analysis

    Each compiler phase takes the output of the one before it. Tokens come before the parse tree, the parse tree before semantic checks, and the checked tree before intermediate code. Optimization works on that intermediate code, so it comes after it.

    Full solution
  11. Q.111 markOfficial answer: B
    ISRO CS 2023 question 11: 2In the context of parsing techniques, LL(1) refers to: (a) Grammars that parse the input from left to right, produce a rightmost derivation, with a lookahead of 1 symbol.Tap to open full size

    Compiler Design › Parsing

    Read LL(k) as: first L = Left-to-right scan of the input, second L = Leftmost derivation, k = number of lookahead symbols. LR parsers instead give a Rightmost derivation in reverse.

    Full solution
  12. Q.121 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 12: 2A host in one organisation is connected to another host in other organisation using 1 Gbps link with 25m sec RTT.Tap to open full size

    Earlier, ISRO's key gave C.

  13. Q.131 markOfficial answer: D
    ISRO CS 2023 question 13: 2In a computer network using CSMA/CD, the minimum frame size for data transfer is 1500 bytes. What will be the data transfer speed in this network over 1 Km cable, if the…Tap to open full size

    Computer Networks › Data link & MAC

    CSMA/CD requires , so the rate that fits the minimum frame to the round trip exactly (and is the highest allowed) is .

    Full solution
  14. Q.141 markOfficial answer: C
    ISRO CS 2023 question 14: 2For internal data communication through computer network, a 5 layer protocol hierarchy is proposed. Applications to be used in this network generate 270 bytes long messages.Tap to open full size

    Computer Networks › Layering & switching

    Every layer adds its own header, so the overhead is (number of layers x header size). Wasted bandwidth is that overhead divided by the total bytes transmitted (payload plus headers).

    Full solution
  15. Q.151 markOfficial answer: A
    ISRO CS 2023 question 15: 2Match the following : Versions of 802.11 Speed of Wireless LAN (i) 802.11ac (P) 7 Gbps (ii) 802.11 a/g (Q) 11 Mbps (iii) 802.11 ad (R) 54 Mbps (iv) 802.11 b (S) 3.5 Gbps…Tap to open full size

    Computer Networks › Data link & MAC

    Remember the peak rate of each 802.11 amendment: b = 11 Mbps, a/g = 54 Mbps, ac = about 3.5 Gbps in the usual textbook figure, ad = about 7 Gbps. Fix the three firm ones first and the last pair follows.

    Full solution
  16. Q.161 markOfficial answer: C
    ISRO CS 2023 question 16: 2Which of the following is true? (a) Both Parity and Cyclic Redundancy Check are error correcting codes (b) Both Parity and Low Density Parity Check Code are error…Tap to open full size

    Computer Networks › Data link & MAC

    Parity and CRC only detect errors. Reed-Solomon and LDPC carry enough structured redundancy to correct them.

    Full solution
  17. Q.171 markOfficial answer: A
    ISRO CS 2023 question 17: 2In Reverse Polish notation, expression A*B+C*D is written as (a) AB*CD*+ (b) A*BCD*+ (c) AB*CD+* (d) A*B*CD+Tap to open full size

    Data Structures and Algorithms › Linear structures

    Apply precedence first, then place every operator after its two operands: the two products are converted separately and the + goes last.

    Full solution
  18. Q.181 markOfficial answer: B
    ISRO CS 2023 question 18: 2In a vectored interrupt (a) The branch address is assigned to a fixed location in memory (b) The interrupting source supplies the branch information to the processor (c)…Tap to open full size

    Computer Organization and Architecture › I/O, interrupts & DMA

    In a vectored interrupt the device sends the vector, which tells the processor where its service routine is, so no polling is needed.

    Full solution
  19. Q.191 markOfficial answer: B
    ISRO CS 2023 question 19: 2For a given finite number of instructions to be executed, which architecture of the processor provides fastest execution?Tap to open full size

    Computer Organization and Architecture › Pipelining

    Execution time is . A super-scalar design issues several instructions per cycle, which lowers CPI below 1 and shortens the run for the same instruction count.

    Full solution
  20. Q.201 markOfficial answer: B
    ISRO CS 2023 question 20: 2An instruction pipeline can be implemented by means of (a) LIFO buffer (b) FIFO buffer (c) Stack (d) None of the aboveTap to open full size

    Computer Organization and Architecture › Pipelining

    Instructions flow through a pipeline in program order, so the buffer holding them between stages must be first-in, first-out (an instruction prefetch queue).

    Full solution
  21. Q.211 markOfficial answer: B
    ISRO CS 2023 question 21: 2The operation executed on data stored in registers is called (a) Macro-operation (b) Micro-operation (c) Bit-operation (d) Byte-operationTap to open full size

    Computer Organization and Architecture › ALU & control unit

    An operation performed on data held in registers is a micro-operation. Each machine instruction is carried out as a sequence of such micro-operations.

    Full solution
  22. Q.221 markOfficial answer: C
    ISRO CS 2023 question 22: 2Which of the following methods is used to detect double errors? (a) Odd Parity (b) Even Parity (c) Checksum (CRC) (d) Checksum (XOR)Tap to open full size

    Computer Networks › Data link & MAC

    Parity and XOR checks are blind to certain even-numbered error patterns, while a CRC with a suitably chosen generator polynomial detects every double-bit error within a frame shorter than the generator's period.

    Full solution
  23. Q.231 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 23: 2The prefix expression is –+abc+d*ef. Evaluate the expression for a = 10,b = 2, c = 5, d = 3, e = 4, f = 1 (a) 3 (b) 4 (c) 10 (d) 6Tap to open full size

    Earlier, ISRO's key gave A.

  24. Q.241 markOfficial answer: C
    ISRO CS 2023 question 24: 2The asymptotic complexity of 4 functions f1, f2, f3, f4 are f1(n) = 2n f2(n) = n(3/2) f3(n) = n log n f4(n) = n(log n) Arrange them in increasing order of complexity (a)…Tap to open full size

    Data Structures and Algorithms › Complexity

    Compare growth rates by dividing out common factors or by taking logarithms: is smaller than any power , a function is super-polynomial but still below because .

    Full solution
  25. Q.251 markOfficial answer: B
    ISRO CS 2023 question 25: 2What is the maximum number of comparisons needed to sort 6 items using radix sort, if each number is a 3-digit decimal number? (a) 120 (b) 180 (c) 210 (d) 360Tap to open full size

    Data Structures and Algorithms › Sorting & hashing

    Radix sort makes one pass per digit, and each pass handles every item against the possible digit values, so the count is with , , .

    Full solution
  26. Q.261 markOfficial answer: D
    ISRO CS 2023 question 26Tap to open full size

    Data Structures and Algorithms › Trees & heaps

    If a node has a left subtree, its inorder predecessor is the rightmost (largest) node of that left subtree: go left once, then right as far as possible.

    Full solution
  27. Q.271 markOfficial answer: A
    ISRO CS 2023 question 27: 2Pointer p to an array of integers (of size 2 Bytes) is initialised to 200. What is the value of p+3? (a) 206 (b) 203 (c) 212 (d) 204Tap to open full size

    Programming in C › Pointers & arrays

    Adding to a pointer advances it by elements, so the address changes by (element type) bytes.

    Full solution
  28. Q.281 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 28: 2In a priority queue, insertion and deletion can be done at (a) Front (b) Back (c) Middle (d) Any positionTap to open full size

    Earlier, ISRO's key gave D.

  29. Q.291 markOfficial answer: A
    ISRO CS 2023 question 29: 2Worst case time complexity of heap sort for n elements (a) O(nlogn) (b) O(logn) (c) O(n2) (d) O(n)Tap to open full size

    Data Structures and Algorithms › Sorting & hashing

    Heap sort builds the heap in and then performs extractions, each a sift-down of at most levels. The total is for every input, and it needs no extra array.

    Full solution
  30. Q.301 markOfficial answer: A
    ISRO CS 2023 question 30: 2Consider a database table T containing two columns X and Y each of type Integer. After the creation of the table, one record (X=1, Y=1) is inserted in the table.Tap to open full size

    Database Management and Warehousing › SQL

    Each new row is built from the current maxima, which always belong to the latest row. So the values follow , giving , while .

    Full solution
  31. Q.311 markOfficial answer: B
    ISRO CS 2023 question 31: 2In SQL the statement select * from R, S is equivalent to (a) Select * from R natural join S (b) Select * from R cross join S (c) Select * from R outer join S (d) Select *…Tap to open full size

    Database Management and Warehousing › SQL

    A comma-separated list of tables in FROM with no condition is the Cartesian product, which is what CROSS JOIN means.

    Full solution
  32. Q.321 markOfficial answer: C
    ISRO CS 2023 question 32: 2Which of the following SQL query deletes all tuples in the teacher relation for those teachers associated with a department located in the building with name CSE and which…Tap to open full size

    Database Management and Warehousing › SQL

    When the condition for a DELETE depends on another table, delete from the target table and filter it with IN (SELECT ...) on the related table.

    Full solution
  33. Q.331 markOfficial answer: D
    ISRO CS 2023 question 33: 2Amongst the ACID properties of a transaction, the 'Durability' property requires that the changes made to the database by a successful transaction persist (a) Except in…Tap to open full size
  34. Q.341 markOfficial answer: A
    ISRO CS 2023 question 34: 2Fifth Normal form is concerned with (a) Join dependency (b) Domain-key (c) Multivalued dependency (d) Functional dependencyTap to open full size

    Database Management and Warehousing › Normal forms

    Each normal form is tied to a kind of dependency. Functional dependencies lead to 2NF, 3NF and BCNF. Multivalued dependencies lead to 4NF. Join dependencies lead to 5NF, also called Project-Join Normal Form.

    Full solution
  35. Q.351 markOfficial answer: A
    ISRO CS 2023 question 35: 2Which of the following definitions is true (i) A digital multiplexer takes one input from many inputs and outputs the selected one (ii) Four select lines are required for…Tap to open full size

    Digital Electronics › Combinational

    A multiplexer picks one of many inputs. A 1-to- demultiplexer needs select lines. An -to- encoder needs only OR gates, one per output bit.

    Full solution
  36. Q.361 markOfficial answer: A
    ISRO CS 2023 question 36: 2The time delay obtained through an 8 bit serial register with 400 MHz clock is : (a) 20 ns (b) 2.5 µs (c) 20 µs (d) 2.5 nsTap to open full size

    Digital Electronics › Sequential

    A serial shift register delays data by one clock period per stage, so total delay = (number of bits) × (clock period).

    Full solution
  37. Q.371 markOfficial answer: C
    ISRO CS 2023 question 37: 2A full adder circuit requires (a) two inputs and two outputs (b) two inputs and three outputs (c) three inputs and two outputs (d) three inputs and one outputTap to open full size

    Digital Electronics › Combinational

    A full adder adds three bits (two operands plus carry-in) and gives a two-bit result: sum and carry-out. A half adder has only two inputs because it has no carry-in.

    Full solution
  38. Q.381 markOfficial answer: D
    ISRO CS 2023 question 38: 2The logical operation of the following circuit is (a) XOR (b) NAND (c) AND (d) OR Y A B YTap to open full size

    Digital Electronics › Boolean logic

    A NAND gate with its inputs tied together is an inverter. A NAND of two inverted signals is an OR gate, by De Morgan's theorem.

    Full solution
  39. Q.391 markOfficial answer: D
    ISRO CS 2023 question 39: 2A logic circuit that provides a LOW output when both inputs are HIGH or both inputs are LOW is (a) AND (b) NAND (c) XNOR (d) XORTap to open full size

    Earlier, ISRO's key gave C.

    Digital Electronics › Boolean logic

    XOR outputs LOW when its two inputs are equal and HIGH when they differ. XNOR is the opposite: HIGH when the inputs are equal.

    Full solution
  40. Q.401 markOfficial answer: D
    ISRO CS 2023 question 40: 2The resulting logic circuit obtained when both inputs of NOR and NAND gates are connected together is: (a) AND (b) XOR (c) OR (d) NOTTap to open full size

    Digital Electronics › Boolean logic

    Joining both inputs of a NAND or NOR gate gives a single-input gate. Because and , the output is , an inverter.

    Full solution
  41. Q.411 markOfficial answer: C
    ISRO CS 2023 question 41Tap to open full size

    Linear Algebra › Eigenvalues

    If one row of a square matrix is a scalar multiple of another, the rows are linearly dependent, the matrix is singular and its determinant is . Look for such a relation before expanding.

    Full solution
  42. Q.421 markOfficial answer: D
    ISRO CS 2023 question 42: 2Which of the following are true? (i) In a graph G with ‘n’ vertices and ‘e’ edges, sum of degrees of vertices = 2*e (ii) Eccentricity of a connected graph can never be…Tap to open full size

    Discrete Mathematics › Graph theory

    Handshaking lemma gives degree sum ; the radius is the smallest eccentricity, so some vertex always attains it; girth is the number of edges in the shortest cycle; equal degrees mean a regular graph, not a multigraph.

    Full solution
  43. Q.431 markOfficial answer: C
    ISRO CS 2023 question 43: 2If there are five faces and nine vertices in an undirected planar graph, then number of edges is (a) 14 (b) 16 (c) 12 (d) None of the aboveTap to open full size

    Discrete Mathematics › Graph theory

    Euler's formula for a connected planar graph, , gives the missing count when two of the three are known. The outer (unbounded) region counts as a face.

    Full solution
  44. Q.441 markOfficial answer: A
    ISRO CS 2023 question 44Tap to open full size

    Probability and Statistics › Counting & axioms

    With equally likely outcomes, probability is favourable count over total count. "Not white" can be counted directly (10 of 15) or found as 1 minus the probability of white.

    Full solution
  45. Q.451 markOfficial answer: D
    ISRO CS 2023 question 45: 2The complexity of matrix multiplication of two matrices A and B whose orders are n m × and p n × respectively is (a) O(m × p) (b) O(m × n2 × p) (c) O(m × n × p2) (d) O(m ×…Tap to open full size

    Data Structures and Algorithms › Complexity

    Count the entries of the result () and multiply by the length of the inner sum for each entry (): three nested loops, each running once over its own dimension.

    Full solution
  46. Q.461 markExcluded from evaluation by ISRO
    ISRO CS 2023 question 46: 2From a character string of length m, the number of sub-strings of all lengths that can be formed are: (a) m2 (b) m (c) m(m+1)/2 (d) m(log m)Tap to open full size

    Earlier, ISRO's key gave C.

  47. Q.471 markOfficial answer: C or D
    ISRO CS 2023 question 47: 2A truth table will need how many rows if there are n variables. (a) 2 *n (b) n (c) 2n (d) None of the aboveTap to open full size

    Earlier, ISRO's key gave C.

    Discrete Mathematics › Mathematical logic

    Every variable doubles the number of possible assignments, so variables give rows.

    Full solution
  48. Q.481 markOfficial answer: A
    ISRO CS 2023 question 48: 2Which of the following multithreading model is followed in Linux OS? (a) One User Thread mapping to One Kernel Thread (b) Many User Threads mapping to One Kernel Thread…Tap to open full size

    Operating Systems › Processes & threads

    Linux creates every thread with clone(), and each thread is a separate kernel task that the scheduler sees. That makes the threading model one-to-one.

    Full solution
  49. Q.491 markOfficial answer: C
    ISRO CS 2023 question 49: 2Purpose of priority inheritance protocol in synchronization mechanisms is (a) To prevent priority inversion in systems having two or lesser priorities for a resource (b)…Tap to open full size

    Operating Systems › Synchronisation

    A lock holder temporarily inherits the priority of the highest-priority task waiting for the lock, so a medium-priority task cannot preempt it and delay the waiter indefinitely.

    Full solution
  50. Q.501 markOfficial answer: C
    ISRO CS 2023 question 50: 2As part of segmentation memory allocation strategy, which of the following assigns segment numbers for various segments of a program like code segment and data segment?Tap to open full size

    Operating Systems › Memory management

    A segment number is an index into the process's segment table. The compiler decides what the segments are (code, data, stack, and so on). The loader builds the segment table when the program is loaded, so it is the loader that numbers the segments and fills in each one's base and limit.

    The question and its official answer
  51. Q.511 markOfficial answer: D
    ISRO CS 2023 question 51: 2Which of the following is false about interrupts ? (a) Interrupts can be triggered by a hardware or by a software (b) Hardware interrupts may be triggered by sending a…Tap to open full size

    Computer Organization and Architecture › I/O, interrupts & DMA

    Hardware interrupts are asynchronous and come from external devices. Traps, exceptions and system calls are synchronous and are raised by the running program (software).

    Full solution
  52. Q.521 markOfficial answer: B
    ISRO CS 2023 question 52: 2 Process Scheduler type Activity (i) Long term scheduler (P) executes much faster to reduce wastage of CPU time (ii) Medium term scheduler (Q) controls degree of multipro…Tap to open full size

    Operating Systems › CPU scheduling

    Long term scheduler: admits jobs and so controls the degree of multiprogramming. Medium term scheduler: swaps processes in and out. Short term scheduler: runs most often, so it must be the fastest.

    Full solution
  53. Q.531 markOfficial answer: C
    ISRO CS 2023 question 53: 2In a producer-consumer scenario also known as Bounded-Buffer Problem, what would be the most appropriate synchronization primitive to ensure that the consumer waits when…Tap to open full size

    Operating Systems › Synchronisation

    A counting semaphore both counts filled slots and blocks or wakes threads, so wait(full) makes the consumer sleep on an empty buffer and signal(full) from the producer wakes it.

    Full solution
  54. Q.541 markOfficial answer: A
    ISRO CS 2023 question 54: 2Any attempt by a process to access memory allocated to OS or process of other user results into (a) Trap to OS (b) Context Switching (c) Page fault (d) Invocation to…Tap to open full size

    Operating Systems › Memory management

    Memory protection hardware catches any access outside a process's own allowed memory and raises a trap, which hands control to the OS in kernel mode.

    Full solution
  55. Q.551 markOfficial answer: A
    ISRO CS 2023 question 55Tap to open full size

    Theory of Computation › Finite automata

    Identify the dead state, then follow the only path that avoids it. Here that path is one from the start, followed by any number of 's looping on the final state.

    Full solution
  56. Q.561 markOfficial answer: B
    ISRO CS 2023 question 56: 2Consider the Nondeterministic Finite- State Automaton (NFA) below. States with a small incoming arrow are initial states, while a double circle state denotes a final state.Tap to open full size

    Theory of Computation › Finite automata

    The NFA accepts strings whose second-to-last symbol is , so a DFA must remember the last two symbols, which gives distinguishable states (Myhill-Nerode).

    Full solution
  57. Q.571 markOfficial answer: A
    ISRO CS 2023 question 57Tap to open full size

    Theory of Computation › CFG & PDA

    Split the grammar into its two parts. generates with , and wraps it with matching pairs of and . So the number of 's exceeds the number of 's by exactly .

    Full solution
  58. Q.581 markOfficial answer: D
    ISRO CS 2023 question 58: 2Which of the following statements is NOT true? (a) If a language is recursive its complement is recursive (b) If a language is recursive its complement is recursively…Tap to open full size

    Theory of Computation › Turing machines

    Recursive languages are closed under complement. A language is recursive exactly when both it and its complement are recursively enumerable. Recursively enumerable languages are not closed under complement.

    Full solution
  59. Q.591 markOfficial answer: B
    ISRO CS 2023 question 59Tap to open full size

    Theory of Computation › Context-free languages

    Context-free languages are closed under union and under intersection with a regular language (product of a PDA and a DFA). The result of that intersection is context-free in general, not regular.

    Full solution
  60. Q.601 markOfficial answer: B
    ISRO CS 2023 question 60Tap to open full size

    Theory of Computation › CFG & PDA

    Unroll the grammar to get a closed form. The rule pairs two 's with one , and gives one followed by any number of 's. So , which has an odd number of 's, all 's first, and at least 's.

    Full solution
  61. Q.611 markOfficial answer: C
    ISRO CS 2023 question 61: 2Which of the following is not a connective of First Order Logic with reference to AI (Artificial Intelligence)? (a) ∧ (b) ∨ (c) <> (d) ¬Tap to open full size

    Artificial Intelligence › Logic

    The connectives of First Order Logic are , , , and . Any other symbol, such as <>, is not one.

    Full solution
  62. Q.621 markOfficial answer: D
    ISRO CS 2023 question 62: 2A hybrid Bayesian network contains (a) Only continuous variables (b) Only discrete variables (c) Both discrete and discontinuous variables (d) Both continuous and discrete…Tap to open full size

    Artificial Intelligence › Uncertainty

    "Hybrid" means the network mixes the two variable types: continuous nodes (often Gaussian) and discrete nodes, linked by conditional distributions such as conditional Gaussians or threshold models.

    Full solution
  63. Q.631 markOfficial answer: A or B
    ISRO CS 2023 question 63: 2Which of the following scenario may not be a good fit for HDFS in Big data paradigm? (a) HDFS is not suitable for scenarios requiring multiple/simultaneous writes to the…Tap to open full size

    Earlier, ISRO's key gave A.

  64. Q.641 markOfficial answer: C
    ISRO CS 2023 question 64: 2A standard Java API for monitoring and managing applications is (a) JVM (b) JVN (c) JMX (d) JMYTap to open full size
  65. Q.651 markOfficial answer: B
    ISRO CS 2023 question 65: 2Which of the following clustering technique is used by K- Means Algorithm: (a) Hierarchical Technique (b) Partitional technique (c) Divisive (d) AgglomerativeTap to open full size

    Machine Learning › Clustering

    Clustering methods are either partitional (one flat set of disjoint clusters, as in K-Means) or hierarchical (a nested tree, built top-down by divisive or bottom-up by agglomerative methods).

    Full solution
  66. Q.661 markOfficial answer: A
    ISRO CS 2023 question 66: 2Which type of data storage system Cassandra is? (a) Distributed (b) Centralized (c) Parallel (d) DumbTap to open full size
  67. Q.671 markOfficial answer: B
    ISRO CS 2023 question 67: 2The cloud infrastructure solely for a single organisation within its premises is (a) public cloud (b) private cloud (c) common cloud (d) hybrid cloudTap to open full size
  68. Q.681 markOfficial answer: C
    ISRO CS 2023 question 68: 2Temporarily renting the capacity to handle spikes in load is called (a) Cloud sharing (b) Cloud computing (c) Cloud bursting (d) Cloud loadingTap to open full size
  69. Q.691 markOfficial answer: A
    ISRO CS 2023 question 69: 2State whether true or false : (i) Virtualisation facilitates multiple OS simultaneously on the same hardware (ii) In dual boot, multiple OS can run simultaneously (a) (i)…Tap to open full size
  70. Q.701 markOfficial answer: B
    ISRO CS 2023 question 70: 2In which of the virtualization techniques, hypervisor modifies the guest OS? (a) Full virtualization (b) Para virtualization (c) Both (a) and (b) (d) None of the aboveTap to open full size
  71. Q.711 markOfficial answer: A
    ISRO CS 2023 question 71: 2Which of the following is the cause of Ping of death issue related to ICMP packets? (a) Buffer overflow (b) Divide by ZERO (c) Missing input sanitisation (d) Privilege…Tap to open full size
  72. Q.721 markOfficial answer: A
    ISRO CS 2023 question 72: 2Match the following and select the correct option: (i) Encryption (P) Manipulation of identification of a host (through NIC identifier) (ii) MAC Cloning (Q) Determining…Tap to open full size
  73. Q.731 markOfficial answer: A
    ISRO CS 2023 question 73: 2Match the following in the context of Information Security which are closely associated (i) Ingress filtering (P) Data leakage prevention (ii) Egress filtering (Q) Hiding…Tap to open full size
  74. Q.741 markOfficial answer: D
    ISRO CS 2023 question 74: 2Asymmetric encryption is not suitable for (a) Confidentiality (b) Authentication (c) Key Exchange (d) Prevention of Denial of ServiceTap to open full size
  75. Q.751 markOfficial answer: C
    ISRO CS 2023 question 75: 2CAPTCHA is used to provide protection from (a) Zero day attack (b) Buffer overflow (c) Automated scripted attack (d) Man in the middle attackTap to open full size
  76. Q.761 markOfficial answer: C
    ISRO CS 2023 question 76: 2The MCDC software testing technique stands for (a) Multiple Conditions Decision Coverage (b) Multiple Coverage Decision Conditions (c) Modified Condition Decision Coverage…Tap to open full size
  77. Q.771 markOfficial answer: C
    ISRO CS 2023 question 77: 2Regression testing focuses on validating (a) module structure (b) module interfaces (c) software changes (d) None of the aboveTap to open full size
  78. Q.781 markOfficial answer: B
    ISRO CS 2023 question 78: 2HIPO chart is also known as (a) UML diagram (b) Structure chart (c) DFD (d) None of the aboveTap to open full size
  79. Q.791 markOfficial answer: B or C
    ISRO CS 2023 question 79: 2McCabe’s cyclomatic complexity number of a program control graph ‘G’ with e edges, n nodes and p disconnected paths is defined as (a) n – e + 2p (b) e – n + 2 + p (c) e…Tap to open full size

    Earlier, ISRO's key gave C.

  80. Q.801 markOfficial answer: A
    ISRO CS 2023 question 80: 2Entity Relationship model shows the (a) Static view (b) Functional view (c) Dynamic view (d) All of the aboveTap to open full size

    Database Management and Warehousing › ER model

    An E-R model captures structure: entities, attributes and relationships. It is a static view. Processes (functional view) and behaviour over time (dynamic view) are modelled with other diagrams.

    Full solution

Part B: Aptitude Q.81 to Q.95

Part B is the same aptitude test as in the ISRO Scientist/Engineer Electronics 2023 paper, held the same day, with the same question numbers. Its solutions are listed under ISRO EC 2023.

  1. Q.811 markOfficial answer: D
    ISRO CS 2023 question 81Tap to open full size

    General Aptitude › Reasoning

    In picture analogies, find the relation in the complete row (material to the tool that applies it) and carry the same relation to the incomplete row.

    Full solution
  2. Q.821 markOfficial answer: D
    ISRO CS 2023 question 82: Which option replaces the question mark? (1 Mark) (a) A (b) B (c) C (d) DTap to open full size

    Earlier, ISRO's key gave B.

    General Aptitude › Spatial

    In a figure analogy, list every change in the example pair separately (outline shape, shading direction, small symbol's fill, orientation and corner) and apply each one exactly as drawn, not as you expect it to behave.

    The question and its official answer
  3. Q.832 marksOfficial answer: B
    ISRO CS 2023 question 83: Which option replaces the question mark? (2 Marks) (a) A (b) B (c) C (d) DTap to open full size

    General Aptitude › Spatial

    Work out which item each operator acts on. Both operators here change only the 1st item, so the 2nd and 3rd items pass through untouched.

    Full solution
  4. Q.841 markOfficial answer: A
    ISRO CS 2023 question 84: You are a retail clerk who typically works Monday through Friday. You arrive at work and notice the new schedule is posted, and your manager has given you a Saturday shift.Tap to open full size
  5. Q.851 markOfficial answer: A
    ISRO CS 2023 question 85: Which of the following best completes the passage below? In a survey of job applicants, two-fifths admitted to being at least a little dishonest.Tap to open full size

    General Aptitude › Reasoning

    To show a survey underestimates a group, find the option that moves members of that group out of the reported count (here, dishonest people who reported being honest). Anything that adds people to the count, or only changes the degree of those already in it, cannot cause an underestimate.

    Full solution
  6. Q.862 marksOfficial answer: A
    ISRO CS 2023 question 86Tap to open full size

    General Aptitude › Reasoning

    In a circular seating puzzle, fix one person, number the seats, and decide which way a person's right hand points from the direction they face (towards the anticlockwise side when facing the centre). Then place people with the direct conditions and test each possible position for the others against the negative conditions.

    Full solution
  7. Q.871 markOfficial answer: A
    ISRO CS 2023 question 87Tap to open full size

    General Aptitude › Reasoning

    The three groups of dominoes alternate between counting down and counting up. The last group must count down again, so with at its end the missing dominoes are and .

    Full solution
  8. Q.881 markOfficial answer: C
    ISRO CS 2023 question 88: Which one will replace the question mark? (1 Mark) (a) 45 (b) 8 (c) 38 (d) 48Tap to open full size

    General Aptitude › Reasoning

    In number-figure puzzles, test the simplest relation first: the sum of the outer numbers compared with the centre. Confirm that one rule fits every complete figure before applying it to the incomplete one.

    Full solution
  9. Q.892 marksOfficial answer: C
    ISRO CS 2023 question 89: Which option replaces the question mark? (2 Marks) (a) A (b) B (c) C (d) DTap to open full size

    General Aptitude › Spatial

    Assign one operation to each symbol using the chains where it appears together with symbols already decoded. Then apply the operations to the query tile in order. Track three things separately: colour, the direction of the diagonal, and the position of the straight line.

    The question and its official answer
  10. Q.901 markOfficial answer: C
    ISRO CS 2023 question 90: Fact 1 : Pictures can tell a story. Fact 2 : All storybooks have pictures. Fact 3 : Some storybooks have words.Tap to open full size

    General Aptitude › Reasoning

    Combine an "all" statement with a "some" statement. The members picked out by "some" also fall under the "all" group, which gives a new "some" statement. A conclusion that brings in an idea the facts never mention (such as "better" or "simple") is not forced.

    Full solution
  11. Q.911 markOfficial answer: D
    ISRO CS 2023 question 91Tap to open full size

    General Aptitude › Reasoning

    A course of action must be a sensible, proportionate response to the problem in the statement. An unverified allegation calls for an inquiry, not punishment, and the regulator's directive is not the thing at fault.

    Full solution
  12. Q.922 marksOfficial answer: D
    ISRO CS 2023 question 92: Find out the wrong number in the series. 7, 8, 18, 57, 228, 1165, 6996 (2 Marks) (a) 7 (b) 8 (c) 6996 (d) 228Tap to open full size

    General Aptitude › Numerical

    When each term is a multiple of the previous one plus a growing amount, find the rule from the early terms, then test whether the later terms continue from it. The wrong term is the one that fails while the terms after it still agree with the rule applied to the correct value.

    Full solution
  13. Q.931 markOfficial answer: A
    ISRO CS 2023 question 93: Directions : The graph given below represents the variations in earnings in rupees over a week. Study the graph and answer questions given below (1 Mark) The difference in…Tap to open full size

    General Aptitude › Data interpretation

    Read each point off the line graph, take the absolute difference for each pair of consecutive days given, and compare. A steep segment of the line marks a large change.

    Full solution
  14. Q.941 markOfficial answer: C
    ISRO CS 2023 question 94Tap to open full size

    General Aptitude › Data interpretation

    Percentage change is the change divided by the starting value, times 100. Here the starting year is 1983.

    Full solution
  15. Q.952 marksOfficial answer: A
    ISRO CS 2023 question 95: What is the maximum area of the rectangle with perimeter 620 mm? (2 Marks) (a) 24,025 mm2 (b) 22,725 mm2 (c) 24,000 mm2 (d) 24,075 mm2Tap to open full size

    General Aptitude › Geometry

    For a fixed perimeter, the rectangle of largest area is a square: with fixed, .

    Full solution