Which kind of class pattern allows only one object of the class to be created throughout the program's lifetime? Identify the design that enforces single-instance control.

Introduction:Sometimes an application needs exactly one global access point to a resource—logging, configuration, or a device manager. This question targets the standard design pattern that enforces a single instance for a class.

Given Data / Assumptions:

• We need at most one instance.
• Global, controlled access is desired.
• Language: C++.

Concept / Approach:The Singleton pattern ensures only one object exists by controlling construction and providing a global accessor. Typical elements include a private constructor, a deleted copy/move, and a static function that returns a reference to the unique instance, often implemented as a function-local static for thread-safe initialization.

Step-by-Step Solution:1) Make constructors private or protected.2) Delete copy/move operations to prevent cloning.3) Provide static T& instance() { static T obj; return obj; }4) Access via T::instance() and never via direct construction.

Verification / Alternative check:Attempts to create additional instances should fail to compile or link; all users obtain the same object reference from the accessor.

Why Other Options Are Wrong:Virtual class: C++ has virtual inheritance, not “virtual classes.”Abstract class: prevents instantiation altogether unless derived and completed.Friend class: an access control tool, not a single-instance mechanism.

Common Pitfalls:Overusing singletons creates hidden dependencies and hinders testing. Prefer dependency injection; use a singleton only when global uniqueness is genuinely required.

Final Answer:Singleton class