What does 'Error LNK2019: unresolved external symbol' mean?
<p>I'm trying to run a program but it won't compile, I get errors. I have changed things, but doesn't seem to work. The code is this:</p>

<pre><code>#include &lt;iostream&gt;
#include &lt;string&gt;
#include "StackLS.h"
using namespace std;


 int main()
   {
int answer;
char symbol;
char n, N;
StackLS stack;
bool balenced = true;

      do {
    cout &lt;&lt; " ********** MENU ********** " &lt;&lt; endl;
    cout &lt;&lt; " 1. Basic Brackets () " &lt;&lt; endl;
    cout &lt;&lt; " 2. Standard Brackets ()[]{} " &lt;&lt; endl;
    cout &lt;&lt; " 3. User-Defined brackets " &lt;&lt; endl;
    cout &lt;&lt; " Please enter your choice: " &lt;&lt; endl;

switch (answer){
case 1: 
    cout &lt;&lt; "Current Setting: () " &lt;&lt; endl;
    cout &lt;&lt; "Enter your expression followed by a ; : " &lt;&lt; endl;
    cin &gt;&gt; symbol;

    do {    

      if (symbol = '(')
    stack.push( '(' );
      else 
      if (symbol = ')' )
      {
      if (stack.isEmpty())
        balenced = false;
            else {
              symbol = stack.top();
        stack.pop();
    }
if (balenced)
    cout &lt;&lt; "Expression is well-formed" &lt;&lt; endl;
else
    cout &lt;&lt; "Expression is not well-formed" &lt;&lt; endl;
       }
           }
    while (symbol != ';' &amp;&amp; balenced);
    stack.pop();

        }
       }
      while (answer != 'n' || 'N');

    } // end main
</code></pre>

<p>I haven't finished the program. I wanted to make sure that what I have so far will compile before I move on to the next case. Now I will post the errors I am getting. They are:</p>

<ol>
<li><p>1>e:\c++ language 2\well-formed expression checker solution\well-formed expression checker project\main.cpp(11): warning C4101: 'n' : unreferenced local variable</p></li>
<li><p>1>e:\c++ language 2\well-formed expression checker solution\well-formed expression checker project\main.cpp(11): warning C4101: 'N' : unreferenced local variable</p></li>
<li><p>1>e:\c++ language 2\well-formed expression checker solution\well-formed expression checker project\main.cpp(22): warning C4700: uninitialized local variable 'answer' used</p></li>
</ol>

<p>1>ManifestResourceCompile:
1>  All outputs are up-to-date.</p>

<ol>
<li><p>1>main.obj : error LNK2019: unresolved external symbol "public: int __thiscall StackLS::top(void)const " (?top@StackLS@@QBEHXZ) referenced in function _main</p></li>
<li><p>1>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall StackLS::push(int const &amp;)" (?push@StackLS@@QAEXABH@Z) referenced in function _main</p></li>
<li><p>1>E:\C++ language 2\Well-Form ed Expression Checker Solution\Debug\Well-Formed Expression Checker Project.exe : fatal error LNK1120: 2 unresolved externals</p></li>
</ol>

<p>Thanks for the help.</p>
