Prefixes of a substring

The prefix of a string $S$ is any string of the form $S[\mathrm{1..}k]$, k \leq \text{size}(S) ($\text{size}(S)$ is the length of a string). Prefix can be either empty or match the string itself. If prefix is not empty and does not match with the string $S$, it is called the proper prefix of string $S$. Print the number of prefixes and all proper prefixes of substring $S[i..j]$ in the increasing order of their lengths.