Abstract Data Types

Definitions

• Abstract data types or ADTs are a mathematical specification of a set of data and the set of operations that can be performed on the data.
• We think of an abstract data type as a type defined in terms of its behavior rather than its implementation.
• Technically, we define an abstract data type as a mathematical object and the operations on that object.

Example :

Strings

ADT

A string is a group of characters that are thought of as a single object.

The operations on strings include :

• finding its length
• concatenation
• copying one string into another
• comparing two strings for equality or for alphabetic ordering
• etc.

Implementation of a string:

A string in C is an array of characters that is pointed to by a pointer whose variable name is the name of the array. The string can be indexed like other arrays. A string is special, because its last character has to be the null terminator.

Strings have many operations on them. Those operations have been written for us and are found in the string library.