The string type holds a sequence of characters. Its operations include the >>, <<, and == operators to read, write, and compare strings, respectively. With this knowledge we can write the code to read the first transaction

double price = 0; // price per book, used to calculate total revenue
// read the first transactions: ISBN, number of books sold, price per book
std::cin >> data1.bookNo >> data1.units_sold >> price;
// calculate total revenue from price and units_sold
data1.revenue = data1.units_sold * price;