ShoppingCartController - StartCheckout doubt

So, I need to customize some code to manage rental products! But I encountered these lines in the StartCheckout method from the ShoppingCartController:

var anonymousPermissed = _orderSettings.AnonymousCheckoutAllowed
                                     && _customerSettings.UserRegistrationType == UserRegistrationType.Disabled;

            if (anonymousPermissed || !await _customerService.IsGuestAsync(customer))
                return RedirectToRoute("Checkout");

            var cartProductIds = cart.Select(ci => ci.ProductId).ToArray();
            var downloadableProductsRequireRegistration =
                _customerSettings.RequireRegistrationForDownloadableProducts && await _productService.HasAnyDownloadableProductAsync(cartProductIds);

            if (!_orderSettings.AnonymousCheckoutAllowed || downloadableProductsRequireRegistration)
            {
                //verify user identity (it may be facebook login page, or google, or local)
                return Challenge();
            }

My question in here is, why is there the negation sign ! in the conditions to check if the current customer is a guest and to check if the AnonymousCheckoutAllowed option is true? Because if the result is false, for example, If my user is not a guest, here, in the condition, the code is going to return true meaning that I am a guess. So what's the purpose of that code in the conditions?

That code says...

        if  AnonymousCheckoutAllowed OR  NOT Guest
            it's ok to proceed to checkout

Hi,

The ! negotiation sign is actually stands for NOT. The code to which you're reffering to is decoded below:

IF ((Checkout_Allowed_Without_Registration AND Registration_Is_Disabled) AND (Current_Customer_Is_Not_Registered)) THEN
Redirect to checkout page
ELSE
Execute next code..

Hope this helps!

Best regards,
Atul