Likely the diagram of the multiphase multi-tape sort diagram that was a foldout in the first edition of TAoCP. As tape fades from memory and usage, the diagram

Likely the diagram of the multiphase multi-tape sort diagram that was a foldout in the first edition of TAoCP. As tape fades from memory and usage, the diagram has been removed. It is a sentimental favorite of mine as tape was important in the early part of my career.