Final answer:
b) Defining custom data structures or types. Atomic (user-defined) objects are used in programming to define custom data structures or types that make it easier to organize and work with complex data in programs.
Step-by-step explanation:
Atomic (user-defined) objects are typically used in programming to define custom data structures or types. These objects allow programmers to create their own data types that can store and manipulate specific sets of data. For example, if a programmer wants to create a data structure to represent a student, they can define an atomic object called 'Student' that contains attributes such as name, age, and grade. This makes it easier to organize and work with complex data in their programs.