Explain the process of paying with a bank card through a terminal: who are the participants involved and how does the interaction occur between them?

The process of paying with a bank card through a terminal involves several key participants and steps:

1. Participants:

• Cardholder — the customer making the purchase.
• Terminal (POS terminal) — the device in the store that reads the card data.
• Acquirer — the bank or organization servicing the terminal and accepting payments from the merchant.
• Issuer — the bank that issued the card to the cardholder.
• Payment system — for example, Visa, MasterCard, which provides routing and transaction standards.

2. Interaction process:

• The customer inserts or taps the card on the terminal and enters the PIN (if required).
• The terminal reads the card data and forms an authorization request.
• The request is sent to the acquirer, which verifies its correctness and forwards it to the payment system.
• The payment system redirects the request to the issuing bank for balance check and operation confirmation.
• The issuer checks the funds availability and security of the operation, then returns a response (approval or decline).
• The response passes back through the payment system and acquirer to the terminal.
• The terminal displays the operation result to the customer and the merchant.

Thus, the process ensures the security and reliability of the payment, using standardized protocols and interactions between banks and payment systems.