Compiling simple C++ program in linux (first time)

I'm getting an error compiling a simple program using c++ in linux. There are 3 files: Employee.h , Employee.cpp, and Salary.cpp (main). I'm including several system headers in Salary.cpp <iostream>, <fstream>, <string>, <stdio.h>, <stdlib.h> The only reason I'm using is for the itoa() function. I could not get it to compile and read somewhere that '' is sometimes a prerequisite.
The error I get is: 'Salary.cpp:195:47: error: itoa was not declared in this scope

Now, I i've included the headers in the global scope, and itoa() is only used in the file that I include so I don't know why this would happen other than it is not including the correct system headers. Do I need to specify all the system headers in the command line or something? I'm not quite sure what is going on.

Edit: Here is some of the source code...I've only expanded on what is needed to keep it short. The error occurs in the addEmployee() function near the bottom...i'm not sure I know how to put line numbers. It's right after create a new Employee()

#include "Employee.h"

#include <iostream>
#include <fstream>
#include <string>
#include <cstdio>
#include <cstdlib>


void findEmployees(Employee*[], const short);
void addEmployee(Employee*[], short&);
unsigned short parseDataFile(Employee* [], short);
bool insertEmployee(Employee*[], short, Employee*);

int main(int argc, char** argv)
{
    //100 employees max, too lazy to create dynamic container
    Employee* employeeList[100];

    //Parse data file, return the length of the list made
    short listLen = parseDataFile(employeeList, 100);

    //Employee database is built, run query engine
    std::cout << "*************************************************\n";
    std::cout << "This program lets you search for salaries of employees or input new employee information.\n";
    std::cout << "*************************************************\n\n\n";

    char choice = { 0 };
    while (true)
    {
        std::cout << "Please choose an option: \n";
        std::cout << "(1) Search for employee salaries.\n";
        std::cout << "(2) Input new employee data\n";
        std::cout << "(3) Exit\n\n";
        std::cin >> choice;

        switch (choice)
        {

        case '1':
            findEmployees(employeeList, listLen - 1);
            break;

        case '2':
            addEmployee(employeeList, listLen);
            break;

        case '3':
            exit(0);
            break;
        }
    }

    return 0;
}

unsigned short parseDataFile(Employee* empList[], short len)
{
    //Do stuff
}

void findEmployees(Employee* empList[], const short len)
{
    //Do stuff
}

void addEmployee(Employee* empList[], short& len)
{
    char first[32] = "";
    char last[32] = "";
    char salary[32] = "";
    char id[32] = "";
    bool loop = true;

    while (loop)
    {
        std::cout << "Input Last Name:  ";
        std::cin.clear();
        std::cin.sync();
        std::cin.getline(last, 31);
        std::cout << std::endl << std::endl;

        std::cout << "Input First Name:  ";
        //Get user name
        std::cin.clear();
        std::cin.sync();
        std::cin.getline(first, 31);
        std::cout << std::endl << std::endl;

        std::cout << "Input Salary:  $";
        //Get user name
        std::cin.clear();
        std::cin.sync();
        std::cin.getline(salary, 31);
        std::cout << std::endl << std::endl;

        Employee* employee = new Employee();
        employee->setID( itoa((int)len, id, 10) ); //Set id

        employee->setFirstName(first); //Set first name
        employee->setLastName(last); //Set last name
        employee->setSalary(salary); //Set salary

        //Inserts new employee at the end of the list, no real reason to sort the list for this assignment
        //I guess I could have used std::vector to make it easy
        empList[len] = employee;
        ++len; //Increment length of the list

        char yesNo = { 0 };
        std::cout << "Would you like to enter another employee?  (Y, N):  ";
        std::cin >> yesNo;
        std::cout << std::endl << std::endl;
        switch (yesNo)
        {
            case 'Y':
            case 'y':
                //do nothing
            break;

            case 'N':
            case 'n':
                loop = false;
            break;

        }        
    }
}