Creating a basic calculator program can be done in many different programming languages. Here's an example of a simple calculator program in Python:

# Function to add two numbers
def add(x, y):
    return x + y

# Function to subtract two numbers
def subtract(x, y):
    return x - y

# Function to multiply two numbers
def multiply(x, y):
    return x * y

# Function to divide two numbers
def divide(x, y):
    return x / y

print("Select operation:")
print("1. Add")
print("2. Subtract")
print("3. Multiply")
print("4. Divide")

choice = input("Enter choice(1/2/3/4): ")

num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))

if choice == '1':
    print(num1, "+", num2, "=", add(num1, num2))

elif choice == '2':
    print(num1, "-", num2, "=", subtract(num1, num2))

elif choice == '3':
    print(num1, "*", num2, "=", multiply(num1, num2))

elif choice == '4':
    if num2 == 0:
        print("Error! Cannot divide by zero.")
    else:
        print(num1, "/", num2, "=", divide(num1, num2))

else:
    print("Invalid input")

You can run this code in a Python environment to create a simple command-line calculator program. Keep in mind that this is just a basic example and can be further enhanced with error handling, input validation, and a graphical user interface depending on your requirements.