Cards were often numbered for finished programs, but during development any change or refactoring would invalidate the numbers and the diagonal lines drawn on t

Cards were often numbered for finished programs, but during development any change or refactoring would invalidate the numbers and the diagonal lines drawn on the side of a deck of cards. Some of the larger comp centers had data processing equipment that would number a stack of cards by punching the card number in the reserved columns 73-80. Card sorters could then sort a mixed up deck using a radix sort in a few passes. See my nearby comments.