To answer directly the first question asked, I made a second pass to demonstrate the feasibility of making a second pass through a set of data records stored on disk.

Oooh. You can read a file twice. N't alota pe'ple know tha'.

The point is, regardless of the "model problem" you chose,

• if you do not store the data from the first pass, then the second pass is useless because you have nothing from the first pass to compare against.
• And if you do store the data from the first pass, the second pass is unnecessary and pointless.

As for your clarification, it's meaningless.