Computer Science Previous Year Questions (page 11)

Explanation

In flowcharts a parallelogram shows input/output, a rectangle shows processing, an oval marks start/end and a diamond marks decisions.

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Machine language is hard to read and modify because it is pure binary and machine-dependent. So "easier to modify" is false.

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Breaking the grammar rules of a language (e.g., a missing semicolon or misspelt keyword) causes syntax errors, which the compiler or interpreter reports.

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Supercomputer speed is measured in FLOPS (floating-point operations per second), e.g., petaFLOPS.

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Form.StartPosition sets where the form first appears when it opens (e.g., CenterScreen or Manual), that is, its initial position.

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The Break All button pauses (breaks) execution of the running program so it can be debugged. It does not delete items.

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Control names must be one word made of letters, digits and underscores. "txtFirst+Last Name" contains a + sign and a space, so it is invalid.

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IDE means Integrated Development Environment: the editor, designer, compiler and debugger combined in one tool.

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In the Visual Studio/VB.NET debugger, F10 is Step Over (it runs a procedure call as one step), F11 is Step Into and F9 toggles a breakpoint.

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The Immediate window shows/evaluates current variable values, the Properties window shows the selected object's properties, Project Explorer lists forms and modules, and the Design window is where the form is designed.

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Object-oriented programming is organised around objects. Procedural programming is built on procedures, functional programming on functions, and logic programming on facts and rules.

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Modular programming breaks a problem into smaller, independent modules that are developed and tested separately.

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Breaking a program into modules makes it easier to use and maintain, and lets the modules be reused in other programs.

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Objects communicate by message passing, that is, one object calls another object's methods.

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A class is a blueprint, and an object is an instance of that class created in memory.

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A class created from an existing class by inheritance is called a derived class (subclass). The existing class is the base class.

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Inheritance, abstraction, polymorphism and encapsulation are OOP features. Abduction is a form of logical reasoning, not an OOP feature.

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Python is case sensitive (Name and name are different variables), so "case insensitive" is not one of its features. It is high-level, interpreted and portable.

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>>> is the prompt of Python's interactive interpreter (shell), meaning it is ready to accept a statement.

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Curly braces holding key : value pairs create a dictionary (dict) in Python.

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Statement II is true: assignment creates a variable and binds a value. Statement I is treated as not true because a variable can only be rebound; values of immutable objects such as strings and tuples cannot be changed in place.

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x //= y is floor division: 125 // 13 = 9 (13 × 9 = 117, remainder 8), so x becomes 9.

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The event queue holds incoming events and decides the order (sequence) in which they are dispatched and handled.

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'All the Best' has 12 characters, so index −3 is index 9. Indexes 8-11 are B, e, s, t, so str1[-3] is 'e'.

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In any binary tree, the number of leaf nodes is one more than the number of nodes with two children, so n leaves means n − 1 nodes of degree 2.

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Start→Next is the node holding 140, and its Next is the node holding 128, so the Info is 128.

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In a 1-based circular queue of size N, it is full (overflow) when Front = 1 and Rear = N, or when Front = Rear + 1 (rear has wrapped round to just behind front).

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In-order traversal of any binary search tree visits the keys in ascending sorted order: 10, 20, ..., 100.

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In an AVL tree, the heights of the left and right subtrees of every node differ by at most 1: |h(TL) − h(TR)| ≤ 1.

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If the item is equally likely to be at any position, the average number of comparisons is (1 + 2 + ... + n)/n = (n + 1)/2.

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For large n the growth order is log n < n < n log n < n² < 2ⁿ.

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Row-major with 1-based indexes, rows before row i hold 3(i−1) − 1 elements, and (i, j) is the (j − i + 2)th element of row i. Total = 3i − 4 + j − i + 2 = 2i + j − 2.

Explanation

The number of distinct BSTs on n keys is the Catalan number C(n) = (2n)!/((n+1)! n!). For n = 6 this is 132.

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Binary search needs at most ⌈log₂(n+1)⌉ comparisons. 2²⁰ = 1,048,576 ≥ 10,00,000, so the maximum is 20.

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177 mod 57 = 177 − 171 = 6 and 197 mod 57 = 197 − 171 = 26.

Explanation

The root is B (last in postorder). Left subtree {E,I,C,F} has root C, with E (right child I) and F. Right subtree {G,D,J,H,K} has root D, with left G and right H (J, K). Preorder: B, C, E, I, F, D, G, H, J, K.

Explanation

Pass 1 merges pairs: (200,470)(80,150)(40,90)(300,400)(70,120). Pass 2 merges runs of two into fours: 80,150,200,470 | 40,90,300,400 | 70,120.

Explanation

Selection sort always makes about n²/2 comparisons, scanning the unsorted part for the minimum on each of n passes, so it is O(n²) in every case.

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A namespace defines a named scope for identifiers, so names such as std::cout do not clash with the same names elsewhere.

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>> with cin is the extraction (get from) operator, and << with cout is the insertion (put to) operator.

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void is used as the return type of a function that returns nothing, and as in f(void) it shows an empty argument list.

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bool holds only two values: true and false.

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A function prototype states the return type, the function name, and the number and types of its arguments.

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The assignment operator is = and it associates right to left, so a = b = c assigns c to b first, then b to a.

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A static member function can access only static members of its class, and it can be called with the class name (Class::f()). So only I is correct.

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The ternary operator ?: is one of the C++ operators that cannot be overloaded, along with ::, . and .*. The other statements about it are true.

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In C++, class members are private by default, while struct members are public by default.

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Overriding redefines an inherited method in a derived class, overloading gives one function or operator several definitions, and a destructor releases memory/resources when an object is destroyed.