Reading a Stream of Fields

---

The previous demonstration shows the insertion operator overloading. Operator overloading can be applied to extraction operator, too. This demonstration performs the following tasks:

• Check whether or not the pair of SSN and ISBN is already in the file buys.txt.
• If it is, overwrite that record.
• If it is not, append the record “SSN|ISBN|quantity” to the end of the file buys.txt.

Purchase Books.
	User's SSN:   Book's ISBN:   Quantity:
Password:

This demonstration shows how to implement the interface by:

• overloading the extraction operator (operator>>) that reads the stream of bytes from the file buys.txt,
• breaking the stream into fields and storing it as a Purchase object,
• copy the values entered from the Web to the Purchase object's values, and
• overloading the insertion operator (operator<<) that writes the Purchase object back to the file.