Too busy to read?

delay at this point has unusually severe financial, as well as psychological, repercussions. The project is fully staffed, and cost-per-day is maximum. More seriously, the software is to support other business effort (shipping of computers, operation of new facilities, etc.) and the secondary costs of delaying these are very high, for it is almost time for software shipment. Indeed, these secondary costs may far outweigh all others. It is therefore very important to allow enough system test time in the original schedule.

Failure to allow enough time for system test, in particular, is peculiarly disastrous. Since the delay comes at the end of the schedule, no one is aware of schedule trouble until almost the delivery date.

Practice is the best of all instructors. --PUBLILIUS

When a task cannot be partitioned because of sequential constraints, the application of more effort has no effect on the schedule (Fig. 2.2). The bearing of a child takes nine months, no matter how many women are assigned.

I have earlier suggested ratios that seem to apply to planning time, coding, component test, and system test. First, one must say that one does not estimate the entire task by estimating the coding portion only and then applying the ratios. The coding is only one-sixth or so of the problem, and errors in its estimate or in the ratios could lead to ridiculous results.

For some years I have been successfully using the following rule of thumb for scheduling a software task: 1/3 planning 1/6 coding 1/4 component test and early system test 1/4 system test, all components in hand.

Because of optimism, we usually expect the number of bugs to be smaller than it turns out to be. Therefore testing is usually the most mis-scheduled part of programming.

our techniques of estimating are poorly developed. More seriously, they reflect an unvoiced assumption which is quite untrue, i.e., that all will go well.

Oversimplifying outrageously, we state Brooks's Law: Adding manpower to a late software project makes it later.

[A ship on the beach is a lighthouse to the sea.] --DUTCH PROVERB