для чего используются

using namespace std;
41. #ifndef CART_H
42. #define CART_H
43. #include <string>
44. #include "ApplicationException.h"
45. class ShoppingCartException : public ApplicationException
46. {
public:
48. ShoppingCartException();
49. ShoppingCartException(string errorMsg);
50. ShoppingCartException(char errorMsg[]);
51. };
52. class ShoppingCart
53. {
54. public:
55. ShoppingCart();
56. void addToCart(string itemDesc) throw(ShoppingCartException);
57. void addToCart(char itemDesc[]) throw(ShoppingCartException);
58. string getItem(string itemDesc) throw(ShoppingCartException);
59. string getItem(char itemDesc[]) throw(ShoppingCartException);
60. string getItem(int itemNumber) throw(ShoppingCartException);
61. private:
62. string *cartItems;
63. int numItems;
64. int allocatedItems;
65. void increaseCartAllocation(int count);
66. };
67. #endif
 
 
и 
 
#include <iostream>
72. #include "ShoppingCart.h"
73. using namespace std;
74. const int ALLOCATE_SIZE = 10;
75. // Implementation of the ShoppingCartException class
76. ShoppingCartException::ShoppingCartException(): ApplicationException()
77. { message = "Error Detected in Shopping Cart Class"; }
78. ShoppingCartException::ShoppingCartException(string errorMsg): ApplicationException()
79. { message = errorMsg; }
80. ShoppingCartException::ShoppingCartException(char errorMsg[]): ApplicationException()
81. { message = errorMsg; }
82. // Implementation of the ShoppingCart class
83. ShoppingCart::ShoppingCart()
84. {
85. cartItems = new string[ALLOCATE_SIZE];
86. numItems = 0;
87. allocatedItems = ALLOCATE_SIZE;
88. }
89. void ShoppingCart::addToCart(string item) throw(ShoppingCartException)
90. {
91. if (numItems == allocatedItems)
92. increaseCartAllocation(ALLOCATE_SIZE);
93. numItems++;
cartItems[numItems - 1] = item;
95. }
96. void ShoppingCart::addToCart(char item[]) throw(ShoppingCartException)
97. {
98. if (numItems == allocatedItems)
99. increaseCartAllocation(ALLOCATE_SIZE);
100. numItems++;
101. cartItems[numItems - 1] = item;
102. }
103. string ShoppingCart::getItem(string itemDesc) throw(ShoppingCartException)
104. {
105. for (int i = 0; i < numItems; i++)
106. if (cartItems[i] == itemDesc)
107. return cartItems[i];
108. throw ShoppingCartException("Item " + itemDesc + " is not in Shopping Cart");
109. }
110. string ShoppingCart::getItem(char itemDesc[]) throw(ShoppingCartException)
111. {
112. string temp = itemDesc;
113. for (int i = 0; i < numItems; i++)
114. if (cartItems[i] == temp)
115. return cartItems[i];
116. throw ShoppingCartException("Item is not in Shopping Cart");
117. }
118. string ShoppingCart::getItem(int itemNumber) throw(ShoppingCartException)
119. {
120. if (itemNumber > numItems - 1)
121. {
122. ShoppingCartException temp("Item number is too large");
123. throw temp;
124. }
125. else
126. return cartItems[itemNumber];
127. }
128. void ShoppingCart::increaseCartAllocation(int count)
129. {
130. allocatedItems += count;
131. string *temp = new string[allocatedItems];
132. for (int i = 0; i < numItems; i++)
133. temp[i] = cartItems[i];
134. cartItems = temp;
135. }