01 What is the esoteric programming language Deadfish?

Deadfish – Esolang (esolangs.org)

Deadfish belongs to the esoteric programming languages and was developed by Jonathan Todd Skinner. It uses the characters i, d, s and o or alternatively the characters x, d, k and c.

Deadfish is difficult to read, cumbersome and inefficient, and intended more as a joke or feasibility study.