What Is an Abstract Data Type in C++?


Larry Thompson

An Abstract Data Type (ADT) is a high-level description of a set of operations that can be performed on a data type, without specifying how the operations are implemented. In C++, an ADT provides a way to encapsulate data and define the operations that can be performed on that data.

Defining an ADT

To define an ADT in C++, you typically create a class. The class serves as a blueprint for creating objects that represent instances of the ADT. The data members of the class define the state of the objects, while the member functions define the operations that can be performed on those objects.


class Stack {
        // Member function declarations
        void push(int value);
        int pop();
        bool isEmpty();
        // Data member declaration
        int stack[100];
        int top;

In this example, we defined an ADT for a stack. The stack class has three member functions: push(), pop(), and isEmpty().

These functions represent the operations that can be performed on a stack. The class also has two data members: stack, which is an array to store the elements of the stack, and top, which keeps track of the top element in the stack.

The Advantages of Using ADTs

The use of ADTs provides several advantages:

  • Data Abstraction: ADTs allow you to abstract away the implementation details and focus on how to use them. This abstraction simplifies code maintenance and modification as you only need to update the ADT’s implementation, without affecting the code that uses it.
  • Code Reusability: ADTs promote code reusability by encapsulating data and operations in a single entity.

    Once an ADT is implemented, it can be used in different programs without having to rewrite the same functionality.

  • Modularity: ADTs promote modularity by dividing a complex problem into smaller, more manageable parts. Each ADT encapsulates a specific set of data and operations, which can be combined to solve larger problems.

Implementing an ADT

To implement an ADT, you define the member functions of the class. Each function should perform the necessary operations on the data members to achieve the desired behavior.


void Stack::push(int value) {
    if (top < 100) {
        stack[top++] = value;

int Stack::pop() {
    if (!isEmpty()) {
        return stack[--top];
    return -1; // Error: Stack is empty

bool Stack::isEmpty() {
    return top == 0;

In this example, we implemented the three member functions of the stack class. The push() function adds an element to the top of the stack if there is space available.

The pop() function removes and returns the top element from the stack if it is not empty. The isEmpty() function checks whether the stack is empty or not.

Using an ADT

To use an ADT, you need to create objects of that class and call its member functions to perform operations on those objects.


Stack myStack;
cout << myStack.pop(); // Output: 30

In this example, we created an object of the stack class called myStack. We pushed three values onto the stack and then popped the top value, which was 30.


An Abstract Data Type (ADT) in C++ allows you to encapsulate data and define the operations that can be performed on that data. By using ADTs, you can abstract away implementation details, promote code reusability, and enhance modularity in your programs. Understanding ADTs is essential for designing and implementing efficient and organized code.

Discord Server - Web Server - Private Server - DNS Server - Object-Oriented Programming - Scripting - Data Types - Data Structures

Privacy Policy