Source Code (Python)

# coding=utf-8

"""
    Simple Calculator
    Performs basic arithmetic operations
"""


def add(num1, num2):
    return num1 + num2


def subtract(num1, num2):
    return num1 - num2


def multiply(num1, num2):
    return num1 * num2


def divide(num1, num2):
    if num2 == 0:
        return "Error: Division by zero is not allowed"
    return num1 / num2


if __name__ == '__main__':
    print("""
    1 - Addition (+)
    2 - Subtraction (-)
    3 - Multiplication (×)
    4 - Division (÷)
    """)
    
    choice = int(input("Select operation (1-4): "))
    num1 = float(input("Enter first number: "))
    num2 = float(input("Enter second number: "))
    
    if choice == 1:
        result = add(num1, num2)
        print("Result: {} + {} = {}".format(num1, num2, result))
    
    elif choice == 2:
        result = subtract(num1, num2)
        print("Result: {} - {} = {}".format(num1, num2, result))
    
    elif choice == 3:
        result = multiply(num1, num2)
        print("Result: {} × {} = {}".format(num1, num2, result))
    
    elif choice == 4:
        result = divide(num1, num2)
        if isinstance(result, str):
            print(result)
        else:
            print("Result: {} ÷ {} = {}".format(num1, num2, result))
    
    else:
        print("Please enter only one of the specified numbers.")