[Dev-C++] Error problems

After compiling the following program and getting no errors, I tried to build 
an executable and received external errors.  Can anyone help me?

//T7AppE08.cpp - displays employee's name, FWT, FICA tax, and net pay

#include <iostream>
#include <string>
using namespace std;

//function prototypes
void getInput(string, float&);
float calcFwt(float, float);
float calcFica(float, float);
float calcNetPay(float, float, float);
void displayInfo(string, float, float, float, float);

int main()
{   
    const float FWT_RATE = float(.2);
    const float FICA_RATE = float(.08);

    string name   = "";
    float salary  = 0.0;
    float fwtTax  = 0.0; 
    float ficaTax = 0.0;
    float netPay  = 0.0;
    
    //enter input items
    getInput(name, salary);

    //calculate taxes
    calcFwt(salary, FWT_RATE);
    calcFica(salary, FICA_RATE);

    //calculate net pay
    calcNetPay(salary, fwtTax, ficaTax);

    //display name, gross, taxes, and net
    displayInfo(name, salary, fwtTax, ficaTax, netPay);

    return 0;
}   //end of main function

//*****program-defined functions*****
void getInput(string name, float salary)
{
    cout << "Enter employee name: ";
    getline(cin, name);
    cout << "Enter weekly salary: ";
    cin >> salary;
}   //end of getInput function

float calcFwt(float salary, const float FWT_RATE, float fwtTax)
{
    fwtTax = salary * FWT_RATE;
    return fwtTax;
}   //end of calcFwt function

float calcFica(float &salary, const float FICA_RATE, float ficaTax)
{
    ficaTax = salary * FICA_RATE;
    return ficaTax;
}   //end of calcFica function

float calcNetPay(float salary, float fwtTax, float ficaTax, float netPay)
{
    netPay = salary - (fwtTax + ficaTax);
    return netPay;
}   //end of calcNetPay function

void displayInfo(string &name, float salary, float fwtTax, float ficaTax, 
float netPay)
{
    cout << fixed;
    cout.precision(2);
    cout << "Employee name: " << name << endl;
    cout << "Gross pay: $" << salary << endl;
    cout << "FWT tax: $" << fwtTax << endl;
    cout << "FICA tax: $" << ficaTax << endl;
    cout << "Net pay: $" << netPay << endl;

}   //end of displayInfo function