tcsh (/ˌtiːˈsiːʃɛl/ "tee-cee-shell", /ˈtiːʃɛl/ "tee-shell", or as an acronym "tee cee ess aitch") is a Unix shell based on and compatible with the C shell (csh). It is essentially the C shell with programmable command-line completion, command-line editing, and a few other features.