In a file allocation system, the following allocation schemes are used: (A) Contiguous allocation, (B) Indexed allocation, (C) Linked allocation. Which allocation scheme(s) will NOT suffer from external fragmentation?

Explanation

External fragmentation arises when free disk space is broken into small, scattered gaps because a file must occupy a contiguous run of blocks — exactly the weakness of contiguous allocation (A), since it needs a sufficiently large free contiguous region. In indexed allocation (B) and linked allocation (C), a file's blocks can be scattered anywhere on disk and are tied together via an index block or in-block pointers respectively, so free space never needs to be contiguous and no external fragmentation results. Hence only B and C avoid external fragmentation, option (iii).