In this paper, we are concerned with finite p-s-composed codes, that i
s with codes obtained by composition of finite prefix and suffix codes
. We give a method to decompose a finite prefix-suffix composed code i
n a minimal number of prefix and suffix codes. Using this method, we e
stablish that every prefix-suffix composed n-word code (n greater than
or equal to 3) can be expressed as the composition of at most 2n - 3
prefix and suffix codes. We show that for all n, this limit is reached
, that is, there exists a ps-composed n-word code that cannot be expre
ssed as the composition of less than 2n - 3 prefix and suffix codes. T
hen we give an example of a three-word code which is not prefix-suffix
composed, refuting a conjecture proposed by Restive et al. in 1989.