dc

Can someone break down what this `dc` command does?

I'm trying to understand the piece of code: `echo '[q]sa[ln0=aln256%Pln256/snlbx]sb5567320342535949633984860024054390510049758475925810612727383477870370412074937779308150930912981042snlbxq'|dc`. What exactly is happening here?