functional and non-functional requirments ?

Question

Hi. I found this case of study here about a game. I am studying a software engineering course, and we learned about the functional and non-functional requirements but what could be possible requirements? Any ideas ?

the document is here Video Games and Software Engineering: A Case Study.

Answer 1

Functional requirements are requirements that can be identified with some specific stimulus and its associated response. So, in a game, the requirement that your POV in a first-person shooter turn right when the right cursor arrow is pressed is a functional requirement.

Non-functional requirements are requirements that don't apply to a specific stimulus and response, but to the system overall. So a non-functional requirement would be that your game needs to support 10 players simultaneously, or that it needs to support a list of different graphics cards.

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Hre are some more examples:

Functional

• Player chooses a weapon from the weapons they are carrying.
• Combat opponent hits player's character; character loses hit points
• Player hits opponent; compute hit probability
• Player fires current weapon; compute impact point
• if response from server ≥ 2 second, post a "waiting..." notice in display
• if password entered doesn't meet 3-4 rule, don't accept, make user retry

Nonfunctional

• Game start up ≤ 30 seconds
• Game should respond to key inputs in ≤ 100 msec
• Server should respond to update location in ≤ 500 msec
• Redraw frame rate ≤ 15 fps
• All passwords must follow a "3 out of 4" rule (ie, must contain characters from at least three of [a-z][A-Z][0-9] and symbols).

Notice the last pair: there's a nonfunctional requirement about password strength; that translates to a functional requirement about what passwords are acceptable. It's useful and important to state both; one specifies how some chunk of software should be built; the other says no part of the software dealing with passwords should violate the rule. So in a sense, the functional requirement is a liveness property: you say what good thing must happen. The nonfunctional requirement is a safety property: you're saying that a particular bad thing must not happen.

Answer 2

There are a lot of places in the document where it mentions functional requirements: e.g. on page 1, it's clear that part of the functionality required is to be able to generate drum-like noises via keyboard input.

The first place which mentioned some non-functional requirements was at the bottom of the left-hand column on page 2, where it says, "With the project time and cost well established from the beginning, the quality etc.": I think that "project time" and "cost" are some examples of non-functional requirements.