I don't see a huge benefit in nailing down a precise definition of what is, and what is not, a magic number. We don't have hard and fast rules about magic numbers at work. Zero and one, for example, will usually survive a code review (though perhaps not if used with bools). There is room for common sense, negotiation and programmer discretion. The focus is on simplicity, clarity and maintainability.

For example, a magic number like 7.4269 that may change in the future being sprinkled all over the place would not survive the review; you'd be asked to choose a meaningful name for it, $customer_interest_rate for example. Even if the number is PI, and so won't ever change, the code will usually be clearer if you use $pi rather than 3.14159.

To be honest, I don't feel strongly about magic numbers and can't ever remember them being a big issue during a code review. There are bigger fish to fry, things like:

• Is the component testable in isolation?
• Is the component interface well-designed?
• Has the programmer gone berserk with unnecessary cleverness?
• Is there a coherent error handling policy?
• Are there gaping security violations?
• Is the program easy to support and troubleshoot remotely?

Obligatory references:

• magic number (wikipedia)
• magic number (stack overflow question)

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