title: LNK2019 - Unresolved External Symbol C++
body: <p>I am new to C++ and have no idea where to look exactly. My program seems to be getting an error labeled as LNK2019 - Unresolved External Symbol.</p>
  
  <p>Exact Message is:
  "error LNK2019: unresolved external symbol "double_cdecl computeSTD(double*const, int)" (?computeSTD@@YANQANH@Z) referenced in function_main)"</p>
  
  <p>If you can provide any advice on how I might learn to fix these types of errors I would be most grateful!</p>
  
  <p>Provided below is a copy of my source code.</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;iomanip&gt; // for Setprecision
  #include &lt;cmath&gt; // for pow and sqrt
  
  using namespace std;
  
  //Prototypes
  void programInformation();
  void inputArrayValues (double array[], int SIZE, int &amp;count);
  void printListOriginal (double array[], int count);
  void sortAscending (double array[], int count);
  double computeAverage (double array[], int count);
  double computeMedian (double array[], int count);
  double computeSTD (double array[], int count);
  void printCalculations (double average, double median, double std);
  
  int main()
  {
      // Declare Local Variables
      const int SIZE=30.0;
      double array[SIZE];
      double average;
      double median;
      double std;
      int count = 0;
  
      // Set Precision for Decimal Points
      cout &lt;&lt; setprecision(1) &lt;&lt; fixed &lt;&lt;showpoint;
  
      // Module Call for Program Infomation
      programInformation();
  
      // Module/Function Calls
      inputArrayValues (array, SIZE, count);
      printListOriginal (array, count);
      sortAscending (array, count);
      average = computeAverage (array, count);
      median = computeMedian (array, count);
      std = computeSTD (array, count);
      printCalculations (average, median, std);
      return 0;
  }
  
  //Module: programInformation
  //Description: Provide the user with the author, title of the program, and its function.
  void programInformation()
  {
      cout &lt;&lt; "*********************************************" &lt;&lt; endl;
      cout &lt;&lt; "***           Author: -                   ***" &lt;&lt; endl; 
      cout &lt;&lt; "***         Statistical Calculator           ***" &lt;&lt; endl;
      cout &lt;&lt; "*********************************************" &lt;&lt; endl;
  }
  
  //Module: inputArrayValues
  //Description: Ask the user to input values between 3 and 30 elements for the array to hold. Also validates that the user inputs a total of values between 3 and 30.
  void inputArrayValues (double array[], int SIZE, int &amp;count)
  {
      double number = 0;
      // Basic information about what the user can input. Does not repeat.
      cout &lt;&lt; "Please enter values one at a time." &lt;&lt;endl;
      cout &lt;&lt; "Up to a maximum of 30 values and a minimum of 3 values." &lt;&lt; endl;
      cout &lt;&lt; "Only positive values are accepted or the program will not work." &lt;&lt; endl;
      cout &lt;&lt; "With the exception, please enter the value -1.0 to stop entering values." &lt;&lt; endl;
  
      // Do-While Loop
      // Variable count is counting how many values the user inputs for later calculation
      while (number != 1.0)
      {
          for (int i = 0; i &lt; SIZE; i++)
          {
              cout &lt;&lt; "Please enter a value or enter -1.0 to stop entering values" &lt;&lt; endl;
              cin &gt;&gt; number;
              array[i] = number;
              if (number != 1.0)
              {
                  count++;
              }
  
          }
      }
  
      if (count &lt; 3 || count &gt; SIZE)
      {
          cout &lt;&lt; "Invalid total number of values." &lt;&lt; endl;
          cout &lt;&lt; "The total number of values must between 3 and 30 values." &lt;&lt;endl;
          cout &lt;&lt; "This program will now close..." &lt;&lt; endl;
          cout &lt;&lt; "Thank you for using this program." &lt;&lt; endl;
      }
  }
  //Module: printListOriginal
  //Description: Prints out the values that the user entered 5 values per line
  void printListOriginal (double array[], int count)
  {
      int i = 0;
      while (i &lt; count)
      {
          cout &lt;&lt;array[i] &lt;&lt; " ";
          i++;
          if (i &gt; 5)
          {
              cout &lt;&lt; endl;
              i= 0;
          }
      }
  }
  //Module: sortAscending
  //Description: Sorts the given inputs in Ascending Order and Displays the sorted list.
  void sortAscending (double array[], int count)
  {
      int i;
      int j = 0;
      double temp;
      for (i = 0; i &lt; count; i++)
      {
          if (array[j+1] &lt; array[j])
          {
              temp = array[j];
              array[j] = array[j+1];
              array [j+1] = temp;
          }
      }
      int k = 0;
      while (k &lt; count)
      {
          cout &lt;&lt;array[k] &lt;&lt; " ";
          k++;
          if (k &gt; 5)
          {
              cout &lt;&lt; endl;
              k= 0;
          }
      }
  }
  //Function: comupteAverage
  //Description: Computes the average of the given inputs.
  double computeAverage (double array[], int count)
  {
      double sum = 0.0;
      double resultA;
      for (int i =0; i &lt; count; i++)
      {
          sum = sum + array[i];
      }
      resultA = sum / count;
      return resultA;
  }
  //Function: computeMedian
  //Description: Computes the Median of the given inputs.
  double computeMedian (double array[], int count)
  {
      double resultM;
      if ((count % 2) == 0)
      {
          resultM = (array[count/2] + (array[count/2] -1.0) /2.0);
      }
      else
          resultM = array[count/2];
      return resultM;
  }
  //Function: computeSTD
  //Description: Computes the Standard Deviation of the given inputs.
  double computeSTD (double array[], int count, double average)
  {
      double temp;
      double sum = 0;
      double resultV;
      for(int i = 0; i &lt; count; i++)
      {
          temp = pow((array[i] - average), 2);
          sum = sum + temp;
      }
      //Account for Sample Standard Deviation N-1
      resultV = sqrt(sum/(count -1));
      return resultV;
  }
  //Module: printCalculations
  //Description: Prints the Average, Median, and Standard Deviation
  void printCalculations (double average, double median, double std)
  {
      cout &lt;&lt; "The average is: " &lt;&lt; average &lt;&lt; endl;
      cout &lt;&lt; "The median is: " &lt;&lt; median &lt;&lt; endl;
      cout &lt;&lt; "The Standard Deviation is: " &lt;&lt; std &lt;&lt; endl;
  }
  </code></pre>