piclist 2009\01\30\095124a >
Thread: Agile programming
face picon face BY : Alan B. Pearce email (remove spam text)

>> Anybody have any thoughts on "margin" as it applies
>> to software?
>It's usually pretty good.  The hosting and bandwidth costs
>amortized over a bunch of customer downloads is probably just
>pennies, but you can sell it for 10s or even 100s of $$.
>Bridges don't have anywhere near those kind of margins.

<VBG> Somehow I don't think that is the kind of margin he means ...

When I read the OP post, I had a thought about it, and the programming
equivalent of 'engineering margins' that would be used for verifying load
bearing on structures, is surely program structure and planning. Keeping
programs modular, easily verified, use of Lint type tools, program path
validation, limit checking, etc is the programmers correspondence to
ensuring load bearing capability on a mechanical item.

The term 'margin' doesn't really come into it, unless you think in terms of
maximum numbers you are likely to encounter (both positive and negative) and
ensure that value fields are in an appropriate format and contain a suitable
number of bits, and that the arithmetical routines can calculate with
sufficient accuracy to maintain the end calculation accuracy required. This
may also require an assessment of the order of calculation (as per the
recent discussion on calculator algorithms) so that accuracy is maintained.

On reading over the above I guess items like ensuring that the processor is
fast enough to complete the algorithm in a require time (I am thinking
embedded closed loop control) requires a worst case speed margin as well.

<FB8C927D16AC49E9992970348FA65D70@space.rl.ac.uk> 7bit

In reply to: <001801c982e5$0565d050$660010ac@radianse.com>
See also: www.piclist.com/techref/microchip/devprogs.htm?key=programming
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Subject (change) Agile programming

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