title: error LNK2019: unresolved external symbol "double __cdecl calculateRetail(double,double)"
body: <p>I'm getting this error:
  <code>error LNK2019: unresolved external symbol "double __cdecl calculateRetail(double,double)" (?calculateRetail@@YANNN@Z) referenced in function _main
  1&gt;c:\users\100236744\documents\visual studio 2010\Projects\Item sales price calculator\Debug\Item sales price calculator.exe : fatal error LNK1120: 1 unresolved externals</code></p>
  
  <p>I am very new to c++.</p>
  
  <pre><code>// FILE: Price markup calculator.cpp
  // PROGRAMMER: Karolina Sabat   CPSC 1103   Section: S11
  // Program which calculates the retail cost of an item based on wholesale cost and mark up percentage. 
  // Calculates the total interest paid based on the annual interest rate.
  
  #include &lt;iostream&gt;         // For cin, cout
  #include &lt;iomanip&gt;          // For setw, setprecision
  using namespace std;
  
  // FUNCTION PROTOTYPES
  void getData (double &amp;, double &amp;);          // Receives USER INPUT - Wholesale cost &amp; percentage markup
  double calculateRetail(double, double);     // Calculates retail price
  void Display (double, double, double);      // Displays results: Wholesale cost, markup percentage, retail price
  
  int main ()
  {
  
  // VARIABLES
  double  wholesale_cost = 0;                 // Wholesale item cost - USER INPUT
  double  markup_percent = 0;                 // Markup percentage
  double  retail_price = 0;               // Calculated retail cost
  
  // FUNCTION CALL 1: Wholesale cost - USER INPUT
  getData(wholesale_cost, markup_percent);
  // FUNCTION CALL 2: Retail price - CALCULATION
  calculateRetail(wholesale_cost, markup_percent); 
  // FUNCTION CALL 3: Display Wholesale price, markup percentage, retail price - OUTPUT
  Display(wholesale_cost, markup_percent, retail_price);
  // PROGRAM MADE BY - OUTPUT
  cout &lt;&lt; endl &lt;&lt; endl;
  cout &lt;&lt; " Written by: Karolina Sabat - CPSC 1103 - Section: S11" &lt;&lt; endl &lt;&lt; endl;
   return 0;
   }
  
  // FUNCTION 1: GetData
  void getData (double &amp;wholesale_c, double &amp;markup_p)
  {
  // Wholesale cost - USER INPUT
  cout &lt;&lt; " Please enter the item's wholesale cost: $ ";
  cin &gt;&gt; wholesale_c;
  // Wholesale cost - INVALID ENTRY 
  while (wholesale_c &lt; 0)
  {
      cout &lt;&lt; endl;
      cout &lt;&lt; " Please enter a wholesale cost greater than 0." &lt;&lt; endl;
      cout &lt;&lt; " Item's wholesale cost: $ ";
      // Will clear characters
      cin.clear();
      cin.ignore(numeric_limits&lt;streamsize&gt;::max(), '\n');
      cin &gt;&gt; wholesale_c;
  }
  // Wholesalecost - VALID
  // Markup percentage - USER INPUT
  cout &lt;&lt; "Please enter the markup percentage: % " ;
  cin &gt;&gt; markup_p;
  // Markup percentage - INVALID
  while (markup_p &lt; 0) 
  {
      cout &lt;&lt; " ERROR: INVALID INPUT." &lt;&lt; endl;
      cout &lt;&lt; " Please enter a markup percentage greater than 0." &lt;&lt; endl;
      cout &lt;&lt; " Markup percentage: % ";
      // Will clear characters
      cin.clear();
      cin.ignore(numeric_limits&lt;streamsize&gt;::max(), '\n');
      cin &gt;&gt; markup_p;
  }
  }
  
  // FUNCTION 2: CalculateRetail
  double CalculateRetail (double wholesale_c, double markup_p)
  {
  // VARIABLES
  double markup_amount;
  double retail_price;
  // CALCULATIONS
  markup_amount = (wholesale_c * markup_p) / 100;
  // Markup amount
  retail_price = wholesale_c + markup_amount;
  return retail_price;
  }
  
  // FUNCTION 3: Display
  void Display (double wholesale_cost, double markup_percent, double retail_price)
  {
  // Title - OUTPUT
  cout &lt;&lt; endl;
  cout &lt;&lt; " WHOLESALE COST: " &lt;&lt; setw(10) &lt;&lt; "PRICE MARKUP %: " &lt;&lt; setw(10) &lt;&lt; "RETAIL PRICE" &lt;&lt; endl;
  cout &lt;&lt; " ________________________________________________________________________________" &lt;&lt; endl;
  cout &lt;&lt; endl;
  // NUMBER FORMATING
  cout &lt;&lt; setprecision(2) &lt;&lt; fixed &lt;&lt; showpoint;
  // Results - OUTPUT
  cout &lt;&lt; " " &lt;&lt; wholesale_cost &lt;&lt; setw(10) &lt;&lt; markup_percent &lt;&lt; setw(10) &lt;&lt; retail_price;
  }
  </code></pre>