Write a program that welcomes the user to the Payroll Calculator and prompts him to enter an employee first name, an employee last name, an hourly rate of pay, and the number of hours worked. The program should display the employee’s net pay assuming a withholding tax rate of 20% and then ask the user if they would like to enter another employee.

To write a program that accomplishes the task you described, you can use a programming language such as Python. Here's an example program that accomplishes this:

```python
def calculate_net_pay(hourly_rate, hours_worked):
gross_pay = hourly_rate * hours_worked
withholding_tax_rate = 0.20
withholding_tax = gross_pay * withholding_tax_rate
net_pay = gross_pay - withholding_tax
return net_pay

def payroll_calculator():
while True:
print("Welcome to the Payroll Calculator!")

first_name = input("Enter the employee's first name: ")
last_name = input("Enter the employee's last name: ")
hourly_rate = float(input("Enter the hourly rate of pay: "))
hours_worked = float(input("Enter the number of hours worked: "))

net_pay = calculate_net_pay(hourly_rate, hours_worked)
print(f"The employee's net pay is: {net_pay}")

another_employee = input("Would you like to enter another employee? (yes/no): ")
if another_employee.lower() != 'yes':
break

payroll_calculator()
```

Explanation:

1. We define a function named `calculate_net_pay`. This function takes in the hourly rate and the number of hours worked, and calculates the net pay by applying a 20% withholding tax rate.

2. We define the main `payroll_calculator` function that handles the user interaction. Inside this function, we continuously prompt the user for employee details and calculate the net pay until the user chooses not to enter another employee.

3. Inside the `payroll_calculator` function, we use the `input` function to retrieve the employee's first name, last name, hourly rate, and hours worked from the user.

4. We then call the `calculate_net_pay` function, passing in the hourly rate and hours worked, and store the result in the `net_pay` variable.

5. Finally, we print the net pay and ask the user if they would like to enter another employee. If the user responds with anything other than "yes" (case insensitive), we break out of the loop and the program exits.

To run this program, you can save it in a file with a .py extension (e.g., `payroll_calculator.py`) and run it using a Python interpreter.