An abstract data type (ADT) is the way we look at a data structure, focusing on what it does and ignoring how it does its job. For example, stacks and queues are perfect examples of an ADT. We can implement both these ADTs using an array or a linked list. This demonstrates the ‘abstract’ nature of stacks and queues.
Data type Data type of a variable is the set of values that the variable can take.
Abstract The word ‘abstract’ in the context of data structures means considered apart from the detailed specifications or implementation
In C, an abstract data type can be a structure considered without regard to its implementation. It can be thought of as a ‘description’ of the data in the structure with a list of operations that can be performed on the data within that structure.
The end-user is not concerned about the details of how the methods carry out their tasks. They are only aware of the methods that are available to them and are only concerned about calling those methods and getting the results. They are not concerned about how they work
For example, when we use a stack or a queue, the user is concerned only with the type of data and the operations that can be performed on it. Therefore, the fundamentals of how the data is stored should be invisible to the user. They should not be concerned with how the methods work or what structures are being used to store the data. They should just know that to work with stacks, they have push() and pop() functions available to them. Using these functions, they can manipulate the data (insertion or deletion) stored in the stack
Advantage of using ADTs
In the real world, programs evolve as a result of new requirements or constraints, so a modification to a program commonly requires a change in one or more of its data structures. For example, if you want to add a new field to a student’s record to keep track of more information about each student, then it will be better to replace an array with a linked structure to improve the program’s efficiency. In such a scenario, rewriting every procedure that uses the changed structure is not desirable. Therefore, a better alternative is to separate the use of a data structure from the details of its implementation. This is the principle underlying the use of abstract data types