B) Explain following term: i) Persistent objects ii) Files

I. Introduction

In the context of Object Oriented Technology, two important concepts are Persistent Objects and Files. Both are used for data storage and retrieval, but they have different characteristics and uses. Understanding these concepts is crucial for effective programming and data management in an object-oriented environment.

II. Persistent Objects

A. Definition

Persistent objects are objects that retain their state or data even after the program that created them has ended. They are stored in a persistent storage medium, such as a database or a file system, and can be retrieved and used by other programs or instances of the same program at a later time.

B. Detailed Explanation

In Object Oriented Programming, objects are instances of classes and they hold data in their fields. However, the data in these objects is typically volatile, meaning it is lost when the program ends or the object is no longer in use. Persistent objects, on the other hand, are designed to retain their data, making it persistent. This is achieved by storing the object's state in a persistent storage medium.

C. Examples

An example of a persistent object could be a User object in a web application. The User object would hold data such as the user's ID, username, and password. This object would be stored in a database, making it persistent. Even if the web application is restarted, the User object's data can be retrieved from the database.

D. Technical Properties

Persistent objects have several technical properties. They can be stored and retrieved from a persistent storage medium, they have longevity (their data is not lost when the program ends), and they maintain their state (the data in their fields).

III. Files

A. Definition

A file is a container in a computer system for storing information. Files are used to store data in a non-volatile storage medium, such as a hard disk or an SSD.

B. Detailed Explanation

Files can hold various types of data, including text, images, audio, and binary data. They are a fundamental component of most operating systems and applications. Files can be read from and written to, allowing data to be retrieved and stored.

C. Examples

Examples of files include a text file that holds a document, a binary file that holds the executable code for a program, or a JPEG file that holds an image.

D. Technical Properties

Files have several technical properties. They have a size (the amount of data they hold), a format (which determines how the data is structured and how it can be read), and they can be read from and written to.

IV. Comparison between Persistent Objects and Files

V. Conclusion

In conclusion, both persistent objects and files are crucial concepts in Object Oriented Technology. They are used for storing and retrieving data, but they have different characteristics and uses. Understanding these concepts is essential for effective programming and data management in an object-oriented environment.

Diagram: Not necessary.

Summary

Persistent objects are objects that retain their state or data even after the program that created them has ended. They are stored in a persistent storage medium, such as a database or a file system, and can be retrieved and used by other programs or instances of the same program at a later time. Files, on the other hand, are containers in a computer system for storing information. They are used to store data in a non-volatile storage medium, such as a hard disk or an SSD. Both persistent objects and files are crucial concepts in Object Oriented Technology and understanding them is essential for effective programming and data management.

Analogy

Persistent objects are like a diary that retains its contents even after the writer has finished writing, while files are like folders that store various types of documents.