From Beyond the Blue Event Horizon (1980) by Frederik Pohl:
Of course, even Albert did not use all sixty billion gigabits all the time. For one thing, they were not all shared. Even the shared stores were occupied by tens of thousands of programs as subtle and complicated as Albert, and by tens of millions of duller ones. The program called “Albert Einstein” slipped through and among the thousands and the millions without interference. Traffic signals warned him away from occupied circuits. Guideposts led him to subroutines and libraries needed to fulfill his functions. His path was never a straight line. It was a tree of branching decision points, a lightning-stroke of zigzag turns and reverses. It was not truly a “path,” either; Albert never moved. He was never in a specific place to move from. It is at least arguable whether Albert “was” anything at all. He had no continuous existence. When Robin Broadhead was through with him and turned him off he ceased to be, and his subroutines picked up other tasks. When he was turned on again he recreated himself from whatever circuits were idle, according to the program S. Ya. had written. He was no more real than an equation, and no less so than God.