It wasn't simply the complexity that was a problem, it was the entire concept of the batch process. Students would prepare their programs on punch cards or paper tape, submit them to the computer operators, and then at some future point receive their output, often to find there was an error and the entire process had to be repeated. As they later put it, "If it takes on the order of 1 day for one try, the student will either lose interest or forget what the problems were. At best, he will waste time standing around waiting for the day's results to appear."