A modular wall segment for constructing a wall includes two walling sheets of selected size and shape bonded to the opposite faces of a plurality of contiguously placed aerated concrete blocks. The BIST sub circuit is to generate a row address pattern or a column address pattern of the memory and includes a boundary address generation circuit for alternately generating a top address and a bottom address of the memory for at least one of the row address pattern and the column address pattern. The mobile field computing device includes memory for storing customer order history data and delivery route data downloaded from a server system.