Payment Application

Payment systems are now available everywhere and everyone interacts with these systems every day.

There are different types of transactions you can make, SALE, REFUND, Pre-Authorization, and VOID.

SALE: means to buy something and its price will be deducted from your bank account. REFUND: this means that you will return something and wants your money back to your bank account. Pre-Authorization: means holding an amount of money from your account, e.g Hotel reservation. VOID: this means canceling the transaction, e.g if the seller entered the wrong amount.

This project implements the SALE transaction only by simulating the card, terminal(ATM), and the server.

Application Flowchart

Modules

Card Module Functions

• getCardHolderName(): This function will ask for the cardholder's name and store it into card data.
• getCardExpiryDate(): This function will ask for the card expiry date and store it in card data.
• getCardPAN(): This function will ask for the card's Primary Account Number and store it in card data.

Terminal Module Functions

• getTransactionDate(): This function will get the system's current date and store it into terminal data.
• isCardExpired(): This function compares the card expiry date with the transaction date.
• getTransactionAmount(): This function asks for the transaction amount and saves it into terminal data.
• setMaxAmount(): This function sets the maximum allowed amount into terminal data.
• isBelowMaxAmount(): This function compares the transaction amount with the terminal max amount.
• isValidCardPAN(): This function checks if the PAN is a Luhn number or not.

Server Module Functions

• retrieveAccountsDatabase(): This function will fill in the global array of ST_accountsDB_t with the valid accounts database.
• updateAccountsDatabase(): This function will update in the global array of ST_accountsDB_t with the valid accounts database.
• recieveTransactionData(): This function will take all transaction data and validate its data.
• isValidAccount(): This function will take card data and validate the PAN.
• isAmountAvailable(): This function will take terminal data and validate the amount.
• saveTransaction(): This function will save all transaction data into the transactions database.

Application Module Functions

• appStart(): This function will start the application.
• main(): This is the main function which runs the application forever.