error LNK2001: unresolved external symbol

[SUPERFLY]

I am unable to figure out why exactly this error keeps occuring, I have tried adding libraries with no prevail.

error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Box::sAlphabet" (?sAlphabet@Box@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A)
fatal error LNK1120: 1 unresolved externals

#include <iostream>
#include <string>
#include <iomanip>
#include <ctime>
#include <cmath>
#include <cstdio>
#include <conio.h>
#include <windows.h>
#include <stdio.h>
using namespace std;

class Box
{
private:
int mX, mY, mSize, mColor, mDirection;
char mLetter[1];
static string sAlphabet;
public:

Box()
{
int alphaIdx;
mSize = 1 + rand() % 4;
mX = mSize + rand() % 76;
mY = mSize + rand() % 21;

do
{
alphaIdx = rand() % sAlphabet.length();
}while(sAlphabet[alphaIdx] == '*');
mLetter[0] = sAlphabet[alphaIdx];
sAlphabet[alphaIdx] = '*';
mColor = rand() % 14 + 1;
mDirection = rand() % 4;
}

void Display()
{
SetColor(mColor);
for(int x = mX; x < mSize + mX; x++)
for(int y = mY; y < mSize + mY; y++)
ConPrintAt(x, y, mLetter, 1);
}
// Program continues

[andywestken]

The linker error is nothing to do with libraries. It's because you have declared but not defined your static member sAlphabet

Add the following at file scope.

string Box::sAlphabet;

Andy