What is meant by data abstraction An example that would be used in a program?

Answer 1

Data abstraction simply describes the difference between an object's concrete implementation and its abstract interface. Clients do not need to know how an object works in order to use it, they only need to know what it does. As a real world example, a user does not need to understand how electrical energy can be transformed into light energy, they only need to know that flicking a switch will turn the light on and off. That is, the switch provides the interface; everything the user needs to know in order to use the light. The implementation details are not important to the user.

In a computer program, we use data abstraction in order to simplify an object's physical representation, exposing only what we need to expose (no more and no less) through an abstract interface whilst keeping the actual implementation details safely tucked away.

As an example, a variable-length array requires at least three pieces of information: the start address of the array, the number of used elements in the array and the number of unused elements in the array. When the programmer wants to add a new element, they must first check to see if there are any unused elements. If not, the array must be reallocated with a new reserve. Then the programmer can add the new element, increment the used element count and decrement the unused element count. And they must do that every time they add a new element.

But these implementation details are not important to the programmer; they simply want to add a new element. The array itself should be responsible for the underlying implementation, not the programmer. And that's where data abstraction comes in. In object oriented programming we use vectors rather than variable length arrays. They both do exactly the same job equally efficiently, but vectors are much easier to work with. The programmer can concentrate on actually using the object rather than concerning themselves with the mundane, repetitive and error-prone activities related to the object's underlying memory management. Those implementation details are safely abstracted away behind the object's interface.