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Past Questions — 2015
An interrupt that can be temporarily ignored is
A)
Vectored interrupt
B)
Non-maskable interrupt
C)
Maskable interrupt
D)
High priority interrupt
A maskable interrupt is one that the processor can temporarily disable or ignore using an interrupt mask. This allows critical code sections to run without being interrupted. In contrast, a non-maskable interrupt cannot be ignored, and vectored/high-priority interrupts describe how interrupts are handled or prioritized, not whether they can be masked.
EPROM contents can be erased by exposing it to
A)
Infrared rays
B)
Burst of microwaves
C)
Ultraviolet rays
D)
Intense heat radiations
EPROM stands for Erasable Programmable Read-Only Memory. Its stored data can be erased by exposing the chip to ultraviolet (UV) light through the quartz window on the package. Infrared rays, microwaves, and intense heat are not the standard method for erasing EPROM contents.
For a binary half sub tractor having two inputs A and B, the correct set of logical expressions for the outputs D (=A minus B) and X (= borrow) are
A)
D=AB+ AB, X = AB
B)
D= AB+AB+ AB, X = AB
C)
D=AB+AB, X = AB
D)
D=AB+AB, X= AB
For a half subtractor, the difference output is the XOR of A and B: D = A ⊕ B = A'B + AB'. The borrow output is 1 only when A = 0 and B = 1, so X = A'B. Option (c) matches these expressions. The other options do not represent the correct XOR difference and borrow logic.
Which of the following algorithm uses ‘divide and conquer’ strategy?
A)
Insertion sort
B)
Quick sort
C)
Shell sort
D)
Selection sort
Quick sort uses the divide and conquer strategy: it divides the array into two subarrays around a pivot, then recursively sorts the subarrays. Insertion sort, Shell sort, and Selection sort are not divide-and-conquer algorithms; they are comparison-based iterative sorting methods.
What is the correct translation of the following statement into mathematical logic? “Some real numbers are rational”
A)
∃x (real(x) v rational(x))
B)
∀x (real(x) → rational(x))
C)
∃x (real(x) ∧ rational(x))
D)
∃x (rational(x) → real(x))
The statement says that there exists at least one number that is both real and rational. In logic, 'some' means existential quantifier (∃), and 'are rational' together with 'real numbers' means the same x must satisfy both predicates, so we use conjunction (∧). Option (a) uses OR, which would mean x is real or rational, not both. Option (b) means all real numbers are rational, which is false. Option (d) is a conditional and does not express that any such number exists.
The DMA controller transfers one data word at a time and after that it returns control of the buses to the CPU is known as
A)
Bus grant
B)
Burst transfer
C)
Cycle stealing
D)
None of these
In DMA, when the controller transfers only one data word (or one memory cycle) at a time and then immediately returns the bus control to the CPU, it is called **cycle stealing**. The DMA 'steals' one bus cycle from the CPU for each transfer.
- **Burst transfer** means DMA takes control of the bus for a whole block of data continuously.
- **Bus grant** is the permission given to use the bus, not the transfer mode.
- Therefore, the correct answer is **Cycle stealing**.
If MSB of a mantissa in a floating point number is non-zero
A)
Number is normalized
B)
Number is negative
C)
Number is positive
D)
None of these
In floating-point representation, a mantissa is said to be normalized when its most significant bit is non-zero (typically 1 in binary). This ensures the number is represented in a standard form with maximum precision. The sign of the number is determined by the sign bit, not by the MSB of the mantissa. Therefore, the correct answer is that the number is normalized.
The technique where the controller is given complete access to main memory is
A)
Cycle stealing
B)
Memory stealing
C)
Memory mode
D)
Burst mode
In DMA, when the controller is given complete access to main memory, it transfers an entire block of data at once. This is called burst mode. In cycle stealing, the controller takes only one memory cycle at a time, not full control. 'Memory stealing' and 'memory mode' are not the standard terms for this technique.
Let P be a QuickSort Program to sort numbers in ascending order using the first element as pivot. Let t1 and t2 be the number of comparisons made by P for the inputs {1, 2, 3, 4, 5} and {4, 1, 5, 3, 2} respectively. Which of the following holds?
A)
t1=5
B)
t1 < t2
C)
t1 > t2
D)
t1 = t2
Using QuickSort with the first element as pivot:
- For input {1, 2, 3, 4, 5}, the pivot is always the smallest element, so each partition is highly unbalanced. The number of comparisons is the maximum possible for 5 elements.
- For input {4, 1, 5, 3, 2}, the first pivot is 4, which partitions the array more evenly, leading to fewer total comparisons than the already-sorted case.
Therefore, the sorted input requires more comparisons than the mixed input, so t1 > t2. However, since the options ask which relation holds and the correct logical relation is t1 > t2, the matching option is (c).
A grammar of the form A → α, Where ‘A’ is a non-terminal (variable) and ‘α’ is combination of non-terminals and terminals (alphabet symbols) is called
A)
Context sensitive
B)
Context Free
C)
Both (a) and (b)
D)
None of these
A grammar rule of the form A → α, where the left-hand side contains exactly one non-terminal A and the right-hand side α can be any string of terminals and/or non-terminals, is the definition of a Context-Free Grammar (CFG). Context-sensitive grammars have rules where the length of the left side is not restricted to a single non-terminal and are generally of the form αAβ → αγβ. Therefore, the correct answer is Context Free.
Which of the following requires less memory?
A)
DFS
B)
BFS
C)
Both (a) and (b)
D)
None of these
Depth First Search (DFS) generally requires less memory than Breadth First Search (BFS). DFS stores only the current path and a limited set of backtracking information, so its space usage is usually proportional to the depth of the search tree. BFS, on the other hand, stores all nodes at the current level before moving to the next level, which can consume much more memory. Therefore, DFS requires less memory.
Pipe-lining is a unique feature of
A)
RISC
B)
CISC
C)
IANA
D)
ISA
Pipelining is a well-known and characteristic feature of RISC (Reduced Instruction Set Computer) architecture, where simple instructions are designed to execute efficiently in overlapping stages. This improves throughput and is one of the key ideas behind RISC processors. CISC processors may also use pipelining, but it is not considered their unique feature. IANA and ISA are not correct in this context.
Worst case complexity of the algorithm to insert an element into a list is
A)
O(n^2)
B)
O(n)
C)
O(log n)
D)
None of these
To insert an element into a list, the worst case occurs when elements have to be shifted to make room for the new element. In a linear list/array, this shifting can take up to n moves, so the worst-case time complexity is O(n). O(n^2) is too high for a single insertion, O(log n) applies to searching in some structures, and 'None of these' is incorrect.
Which of the following is not part of instruction cycle?
A)
Fetch
B)
Write
C)
Decode
D)
Execute
The instruction cycle typically consists of Fetch, Decode, Execute, and sometimes Store/Write-back. In the standard basic instruction cycle, Fetch, Decode, and Execute are core stages. 'Write' is not usually listed as a separate basic stage of the instruction cycle; it is generally part of the write-back or store phase after execution.
Regular expression are
A)
Type 0 language
B)
Type 1 language
C)
Type 2 language
D)
Type 3 language
In the Chomsky hierarchy, regular languages are the simplest class and are generated by regular expressions and recognized by finite automata. Regular languages correspond to Type 3 languages. Type 0 is unrestricted, Type 1 is context-sensitive, and Type 2 is context-free, so those options are incorrect.
A logically related instructions or data elements associated with a name is called
A)
Logical address
B)
Page
C)
Segment
D)
None of these
In memory management, a **segment** is a logically related collection of instructions or data elements associated with a name. Segmentation divides a program into meaningful parts such as code, data, stack, etc. A **logical address** is just an address generated by the CPU, and a **page** is a fixed-size block used in paging, not a named logical unit.
BCD of 761 is
A)
011101100001
B)
1111101
C)
0111110001
D)
None of these
In BCD (Binary Coded Decimal), each decimal digit is represented separately by 4 bits.
For 761:
- 7 = 0111
- 6 = 0110
- 1 = 0001
So, BCD of 761 = 0111 0110 0001 = 011101100001.
Option (b) is the pure binary form of 125, not BCD of 761. Option (c) does not correctly encode 761 in BCD. Hence, option (a) is correct.
A priority queue is implemented as a Max-Heap. Initially, it has 5 elements. The level-order traversal of the heap is: 10, 8, 5, 3, 2. Two new elements 1 and 7 are inserted into the heap in that order. The level-order traversal of the heap after the insertion of the elements is
A)
10, 8, 7, 3, 2, 1, 5
B)
10, 8, 7, 2, 3, 1, 5
C)
10, 8, 7, 1, 2, 3, 5
D)
10, 8, 7, 5, 3, 2, 1
A max-heap keeps the largest element at the root, and after each insertion the new element is placed at the end and then percolated up if needed.
Initial heap (level order): 10, 8, 5, 3, 2
1) Insert 1:
- Place 1 at the next available position.
- Since 1 is smaller than its parent, no swapping is needed.
- Heap becomes: 10, 8, 5, 3, 2, 1
2) Insert 7:
- Place 7 at the next available position.
- Compare 7 with its parent 5.
- Since 7 > 5, swap them.
- Now 7 is below 10, and 7 < 10, so stop.
Final heap level order: 10, 8, 7, 3, 2, 1, 5
So the correct option is (a).
A minimal spanning tree of a graph G is
A)
A spanning sub graph
B)
A tree
C)
Minimum weights
D)
All of these
A minimal spanning tree (MST) is a spanning subgraph that is a tree and has minimum total edge weight among all spanning trees of the graph. So it is correctly described by all three statements: it is a spanning subgraph, it is a tree, and it has minimum weight. Therefore, the correct option is (d) All of these.
Moore machine depends on
A)
Input
B)
Present State
C)
Both (a) and (b)
D)
None of these
A Moore machine is a finite state machine whose output depends only on the present state, not directly on the current input. In contrast, a Mealy machine’s output depends on both the present state and the input. Therefore, the correct option is (b) Present State.
A graph is called a ___ if it is a connected acyclic graph.
A)
Cyclic graph
B)
Regular graph
C)
Tree
D)
Not a graph
A connected graph with no cycles is called a tree. 'Acyclic' means it has no cycles, and 'connected' means every pair of vertices is joined by a path. Hence the correct term is Tree. The other options are incorrect because a cyclic graph has cycles, a regular graph is defined by equal vertex degrees, and 'not a graph' is false.
When an unit receives data it responded with another control signal to acknowledge the receipt of the data, this is known as
A)
Strobe
B)
Interrupt
C)
Polling
D)
Handshaking
In computer organization, when a device receives data and sends back a control signal to acknowledge that the data has been received, the process is called handshaking. It is a two-way coordination method used to synchronize data transfer between sender and receiver. Strobe uses a single control signal, interrupt is for alerting the CPU of an event, and polling is checking devices one by one for service.
Which of the following is not height-balanced tree?
A)
AVL Tree
B)
B-Tree
C)
Read-black Tree
D)
None of these
AVL trees, B-trees, and Red-Black trees are all height-balanced tree structures, though they use different balancing rules. AVL trees maintain strict balance by keeping the height difference of subtrees at most 1. Red-Black trees ensure approximate balance through color properties, giving logarithmic height. B-trees are also balanced multiway search trees used in databases and file systems. Therefore, none of the given trees is 'not height-balanced'.
Selection and Insertion sort are similar in respect of
A)
Asymptotic complexity
B)
Non recursive
C)
Non-linear operation
D)
None of these
Selection sort and insertion sort are both simple iterative sorting algorithms that do not use recursion. Hence, they are similar in respect of being non-recursive. Their asymptotic complexities are also the same in the average and worst case, but the most direct common feature among the given options is that both are non-recursive. Option (c) is incorrect because both are linear-time based comparison sorts on arrays/lists, not non-linear operations. Option (d) is incorrect because option (b) is correct.
Difference between state table and excitation table is
A)
Excitation table has flip-flop inputs
B)
State table has flip-flop inputs
C)
No differences
D)
None of these
A state table shows the present state, input, next state, and output of a sequential circuit. An excitation table, on the other hand, tells what flip-flop input values are required to achieve a desired transition from present state to next state. Therefore, the excitation table contains flip-flop inputs, while the state table does not. Hence, option (a) is correct.