Modularity

Degree to which system is capable of being assembled and disassembled with multiple parts at reasonable cost

Examples

• Laptop is more modular than cup as harddrive can be replaced which handle of cup is not replaceable.
• Modular software has many components which are independent and replaceable.

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Abstraction

It is act of finding common essential properties among set of objects and also, differentiating that set from other sets.

Examples

• Classifcation of anything e.g. taxonomy in biology
• Defining classes or common set of objects in OO languages

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Encapsulation

Limiting access to private implementation only by public interface

Examples

• In a restaurant, customer has limited access to kitchen via waiter.
• In OO language, data members in class are kept private with public getters/setters as per context

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Polymorphism

Limiting access to multiple different private implementations by single public interface

Examples

• If you learn to drive one car, you learn to drive almost all other cars.
• In OO language, same interface is implemented by multiple classes.

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Hierarchy

Reverse tree like stucture

Examples

• Inheritance tree of classes in OO language
• 'Part of' relationship among parts of composite object