Page 35 - The Art of Designing Embedded Systems

22 THE ART OF DESIGNING EMBEDDED SYSTEMS

What does it cost to inspect code? We do inspections because
they have a significant net negative cost. Yet sometimes manage-
ment is not so sanguine; it helps to show the total cost of an inspec-
tion assuming there’s no savings from downstream debugging.
The inspection includes four people: the Moderator, Reader,
Recorder, and Author. Assume (for the sake of discussion) that these
folks average a $60,000 salary, and overhead at your company is
100%. Then:
One person costs: $120,000 = $60,000 x
2 (overhead)
One person costs: $58/hr = $120,000/2080 work
hours /year
Four people cost: $232/hr = $58/hr x 4
Inspection cost/line: $1.54 = $232 per hour/l50 lines
inspected per hour
Since we know code costs $20-50 per line to produce, this
$1.54 cost is obviously in the noise.

For more information on inspections, check out Soware Inspection,
Tom Gilb and Dorothy Graham, 1993, TJ Press (London), ISBN 0-201-
63 18 1-4, and Software Inspection-An Industry Best Practice, David
Wheeler, Bill Brykczynski, and Reginald Meeson, 1996 by IEEE Com-
puter Society Press (CA), ISBN 0-8 186-7340-0.

Step 4: Create a Quiet Work Znvironment
For my money the most important work on software productivity in
the last 20 years is DeMarco and Lister’s Peopleware (1987, Dorset House
Publishing, New York). Read this slender volume, then read it again, and
then get your boss to read it.
For a decade the authors conducted coding wars at a number of dif-
ferent companies, pitting teams against each other on a standard set of
software problems. The results showed that, using any measure of per-
formance (speed, defects, etc.), the average of those in the first quartile
outperformed the average in the fourth quartile by a factor of 2.6. Surpris-
ingly, none of the factors you’d expect to matter correlated to the best and
worst performers. Even experience mattered little, as long as the program-
mers had been working for at least 6 months.