Technical Quiz R1

What is virtual inheritance in C++?

• C++ technique to enhance multiple inheritance

• C++ technique to ensure that a private member of the base class can be accessed somehow

• C++ technique to avoid multiple inheritances of classes

• C++ technique to avoid multiple copies of the base class

  into children/derived class

Answer explanation

Virtual inheritance in C++ is a technique used to prevent multiple copies of a base class when using multiple inheritance. This ensures that derived classes share a single instance of the base class, avoiding ambiguity and redundancy.

Which sorting algorithm is the most efficient for large datasets?

• Bubble Sort

• Insertion Sort

• Quick Sort

• Selection Sort

Answer explanation

Quick Sort is the most efficient for large datasets due to its average time complexity of O(n log n), making it faster than Bubble Sort, Insertion Sort, and Selection Sort, which have worse average performance.

What is the difference between delete and delete[] in C++

• delete is syntactically correct but delete[] is wrong and hence will give an error if used in any case

• delete is used to delete normal objects whereas delete[]

• delete is a keyword whereas delete[] is an identifier

• delete is used to delete single object whereas delete[] is used to multiple(array/pointer of) objects

Answer explanation

The correct choice states that 'delete' is used for a single object, while 'delete[]' is for multiple objects (arrays). Using 'delete[]' on a single object or 'delete' on an array can lead to undefined behavior, making this distinction crucial.

In a relational database, which key uniquely identifies a record in a table?

• Foreign Key

• Candidate Key

• Primary Key

• Composite Key

Answer explanation

The Primary Key uniquely identifies each record in a table, ensuring that no two records have the same key value. Other keys like Foreign Key and Composite Key serve different purposes in relational databases.

Which of these statements is incorrect about Thread?

• start() method is used to begin execution of the thread

• run() method is used to begin execution of a thread before start() method in special cases

• A thread can be formed by implementing Runnable interface only

• A thread can be formed by a class that extends Thread class

Answer explanation

The statement about the run() method is incorrect because the run() method does not start a thread; it is executed when the thread is started using the start() method. The start() method is essential for thread execution.

What is Truncation in Java?

• Floating-point value assigned to a Floating type

• Floating-point value assigned to an integer type

• Integer value assigned to floating type

• Integer value assigned to floating type

Answer explanation

Truncation in Java occurs when a floating-point value is assigned to an integer type, resulting in the loss of the decimal part. This is why the correct answer is 'Floating-point value assigned to an integer type'.

Which of these is not a correct statement?

• Every class containing abstract method must be declared abstract

• Abstract class defines only the structure of the class not its implementation

• Abstract class can be initiated by new operator

• Abstract class can be inherited

Answer explanation

The statement 'Abstract class can be initiated by new operator' is incorrect. Abstract classes cannot be instantiated directly; they must be subclassed and the subclass can be instantiated.

In E-R model, Y is the dominant entity and X is subordinate entity

• If X is deleted, then Y is also deleted

• If Y is deleted, then X is also deleted

• If Y is deleted, then X is not deleted

• None of the above

Answer explanation

In an E-R model, if Y is the dominant entity, deleting Y will also delete the subordinate entity X, as X's existence depends on Y. Therefore, the correct choice is: If Y is deleted, then X is also deleted.

The relation schemas R1 and R2 form a Lossless join decomposition of R if and only if: (a) R1 0 R2 (R1-R2)

• (a) and (b) happens

• (a) and (d) happens

• (a) and (c) happens

• (b) and (c) happens

Answer explanation

The relation schemas R1 and R2 form a Lossless join decomposition if (a) R1 ∩ R2 = R1 - R2 and (c) R1 ∩ R2 = R2 - R1. Thus, the correct choice is (a) and (c) happens.

Which of the following statements is FALSE about weak entity set?

• Weak entities can be deleted automatically when their stro ng entity is deleted.

• Weak entity set avoids the data duplication and consequen t possible inconsistencies caused by duplicating the key of the strong entity.

• A weak entity set has no primary keys unless attributes of t he strong entity set on which it depends are included

• Tuples in a weak entity set are not partitioned according to their relationship with tuples in a strong entity set.

Answer explanation

The statement about weak entity sets not being partitioned according to their relationship with strong entities is false. Weak entities are defined by their dependence on strong entities, which influences their organization.