This paper initiates the study of $k$-catalytic branching programs, a nonuniform model of computation that is the counterpart to the uniform catalytic space model of Buhrman, Cleve, Koucky, Loff and Speelman (STOC 2014). A $k$-catalytic branching program computes $k$ boolean functions simultaneously on the same $n$-bit input. Each function has ... more >>>