Branching programs are computation models
measuring the space of (Turing machine) computations.
Read-once branching programs (BP1s) are the
most general model where each graph-theoretical path is the computation
path for some input. Exponential lower bounds on the size of read-once
branching programs are known since a long time. Nevertheless, there are only
few functions where the BP1 size is asymptotically known exactly.
In this paper, the exact BP1 size of a fundamental function, the
direct storage access function, is determined.