The document discusses designing a two-floor elevator using digital logic. It defines variables to represent the present floor, last selected floor, an up command, down command, and open door command. Based on these variables, it derives Boolean expressions for the up, down, and open door commands using a truth table and K-map. The key variables are P for present floor, L for last selected floor, U for up command, D for down command, and OP for open door command.