State of Mind in a Marathon Coding Session

The peak hour itself was tremendously intense, but during the hours before, and even during the hours afterward, a hacker attained a state of pure concentration. When you programmed a computer, you had to be aware of where all the thousands of bits of information were going from one instruction to the next, and be able to predict—and exploit—the effect of all that movement. When you had all that information glued to your cerebral being, it was almost as if your own mind had merged into the environment or the computer. Sometimes it took hours to build up to the point where your thoughts could contain that total picture, and when you did get to that point, it was such a shame to waste it that you tried to sustain it by marathon bursts, alternately working on the computer or poring over the code that you wrote on one of the offline Flexowriters in the Kluge Room. You would sustain that concentration by “wrapping around” to the next day.

There is a point where you have the whole program in your head at once, one with it, and you don't want to let it go, so you keep working in a marathon burst of energy.