The True Cost of Debugging
When he arrived, he walked around for a few minutes, surveying the presses; then he approached one of the control panels and opened it. He removed a dime from his pocket, turned a screw 1/4 of a turn, and said, “The presses will now work correctly.” After being profusely thanked, he was told to submit a bill for his work.
The bill arrived a few days later, for $10,000.00! Not wanting to pay such a huge amount for so little work, the printer was told to please itemize his charges, with the hope that he would reduce the amount once he had to identify his services. The revised bill arrived: $1.00 for turning the screw; $9,999.00 for knowing which screw to turn.
Commentary: most debugging problems are fixed easily; identifying the location of the problem is hard.