Abstract Data Types (ADT)

The interface layer between logic and implementation

What is an ADT?

An Abstract Data Type (ADT) is a mathematical model for data types defined by its behavior (operations), not its implementation. It separateswhat a data structure does from how it does it.

Think of an ADT as a contract: it defines what operations are available and what they do, leaving the implementation details to concrete data structures.

ADT Examples

Stack ADT — implemented via Array or Linked List
Queue ADT — implemented via Array or Linked List
List ADT — implemented via Array or Doubly Linked List
Map ADT — implemented via Hash Table or BST
Priority Queue ADT — implemented via Heap

ADT vs Data Structure

ADT (Abstract)

• Defines operations (push, pop, peek)
• Specifies behavior, not implementation
• Language-independent concept
• The "what"

Data Structure (Concrete)

• Defines storage and algorithms
• Memory layout decisions
• Language-specific implementation
• The "how"

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