C++ program that simulates a soft drink machine

Drink Machine Simulator
Write a C++ program that simulates a soft drink machine. The program should use a stru cture
that stores the following data:Drink Name
Drink Cost
Number of Drinks in Machine
The program should create an array of five structures. The elements should be initialized
with the following data:

Drink Name                         Cost                           Number in Machine
Cola                                     .75                                       20
Root Beer                             .75                                       20
Lemon-Lime                          .75                                       20
Grape Soda                           .80                                       20
Cream Soda                          .80                                       20

Each rime the program runs, it should enter a loop that performs the following
steps: A list of d rinks is displayed on the screen. The user should be allowed to
either quit the program or pick a drink. 11 the user selects a drink. he or she will
next enter the amount of money that is to be inserted into the drink machine. The
program should display the amount of change that would be returned and subtract
one from the number of that drink left in the machine. If the user selects a drink thar
has sold Out, a message should be displayed. The loop then repeats. When the user
chooses to quit the program it should display the total amount of money the
machine earned.
Input Validation: When the user enters an amount of money, do not accept negative
values, or values greater than $1.00.

Answer:

//  Drink Machine Simiulator
#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <cstring>
using namespace std;

// Constants for arrays
const int NAME_SIZE = 12;
const int NUM_DRINKS = 5;

// Declaration of the Drink structure
struct Drink
{
   char name[NAME_SIZE]; // Drink name
   double price;         // Price of the drink
   int num;              // Number of cans in the machine
};

// Function prototypes
int getChoice(Drink []);
void transaction(Drink [], int, double &);

int main()
{
   // Menu choice
   int choice;
   
   // Drink machine earnings
   double earnings = 0;
   
   // Array of drinks in the machine
   Drink machine[NUM_DRINKS] = {
                       {"Cola     ", 0.75, 20},
                       {"Root Beer", .75, 20},
                       {"Lemon-Lime", .75, 20},
                       {"Grape Soda", .80, 20},
                       {"Cream Soda", .80, 20}};

   // Set the floating-point output formatting.
   cout << fixed << showpoint << setprecision(2);
   
   // Display the menu and process the user's choice.
   choice = getChoice(machine);
   while (choice != 5)
   {
      // Process the transaction.
      transaction(machine, choice, earnings);
      
      // Get the next choice.
      choice = getChoice(machine);
   }
   
   // Display the machine's total earnings
   cout << "Total earnings: $" << earnings << endl;
   return 0;
}

//****************************************************
// Function getChoice                                *
// This function gets the user's choice and returns  *
// that value minus one. This adjustment is made     *
// because the value will be used as a subscript     *
// into the Drink array by the transaction function. *
//****************************************************

int getChoice (Drink m[])
{
   // The user's choice
   int choice;

   cout << endl;
   
   // Display a list of drinks preceded by a number.
   // This will be the menu.
   for (int x = 0; x < NUM_DRINKS; x++)
   {
      cout << (x+1) << ") " << m[x].name << "\t\t";
      cout << m[x].price << endl;
   }
   
   // Display the last menu item, which is to
   // leave the drink machine.
   cout << (NUM_DRINKS + 1) 
        << ") Leave the drink machine\n\n";

   // Get the user's choice.
   cout << "Choose one: "; cin >> choice;
   
   // Validate the choice.
   while (choice < 1 || choice > 6)
   {
      cout << "Bad choice. Choose one: "; cin >> choice;
   }

   // Return the choice, as a subscript into
   // the array of drinks.
   return choice - 1;
}

//****************************************************
// Function transaction                              *
// This function processes the user's choice and     *
// updates the eranings variable.                    *
//****************************************************

void transaction(Drink m[], int choice, double &earnings)
{
   // The amount of money tendered
   double money;

   // If the selected drink is sold out, display a
   // message and get out of this function.
   if (m[choice].num == 0)
   {
      cout << "Sorry, that selection is sold out.\n";
      return;
   }

   // Get some money from the customer.
   cout << "Enter an amount of money: "; cin >> money;

   // Make sure the customer entered at least enough
   // for the selected drink, and no more than $1.00.
   while(money < m[choice].price || money > 1.0)
   {
      cout << "Enter at least " << m[choice].price;
      cout << " and not more than 1 dollar.\n"; cin >> money;
   }
   
   // Process the selection and give back any
   // change that is due.
   if (money >= m[choice].price)
   {
      // Dispense the drink.
      cout << "\nThump, thump, thump, splat!\n"
           << "Enjoy your beverage!\n\n";
           
      // Calculate any change that is due.
      cout << "Change calculated: " 
           << (money - m[choice].price) 
           << endl; // If change is due, give it to the customer. if ((money - m[choice].price)>0)
         cout << "Your change, " << (money - m[choice].price)
              << " has just dropped into the Change Dispenser.\n\n";
      
      // Update our earnings.
      earnings += m[choice].price;
      
      // Decrease the number of cans of the selected
      // drink currently in the machine.
      m[choice].num--;
      
      // Display the number of cans of this drink
      // currently in the machine.
      cout << "There are " << m[choice].num 
           << " drinks of that type left.\n";
   }
}