
It is a very humbling experience to make a multimillion-dollar mistake, but it
is also very memorable.  I vividly recall the night we decided how to organize
the actual writing of external specifications for OS/360.  The manager of
architecture, the manager of control program implementation, and I were
threshing out the plan, schedule, and division of responsibilities.

The architecture manager had 10 good men.  He asserted that they could write
the specifications and do it right.  It would take ten months, three more
than the schedule allowed.

The control program manager had 150 men.  He asserted that they could prepare
the specifications, with the architecture team coordinating; it would be 
well-done and practical, and he could do it on schedule.  Futhermore, if
the architecture team did it, his 150 men would sit twiddling their thumbs
for ten months.

To this the architecture manager responded that if I gave the control program
team the responsibility, the result would not in fact be on time, but would
also be three months late, and of much lower quality.  I did, and it was.  He
was right on both counts.  Moreover, the lack of conceptual integrity made
the system far more costly to build and change, and I would estimate that it
added a year to debugging time.
- Frederick Brooks Jr., "The Mythical Man Month" 
