What is a permuted index?

Question

I am reading Accelerated C++. I don\'t understand Exercise 5-1:

Design and implement a program to produce a permuted index from the following input. A per

Answer 1

You can find a 'live' example of a permuted index in the 7th Edition UNIX™ Programmer's Reference Manual, Vol 1 (dating back to 1979). A fragment of it (from the PDF files) is:

If you look for 'account', you can find a number of related entries together. You probably wouldn't think to look for sa(1) as well as ac(1), not to mention acct(2) or acct(5) unless they were grouped together. This is the benefit of a permuted index; you can look up the key word and see it in a bigger context.

You could also look at the man page entry for the ptx(1) command in the same 7th Edition manual.