4-4 Boolean Analysis of Logic Circuits 3. Truth table(真值表) Constructing the truth table from a logic expression (1) Determine the number of the input and output variables, and the number of the input variable possible ble combinations 2)Draw the truth table frame according to the input and output variables4 4-4 Boolean Analysis of Logic Circuits 3. Truth Table （真值表）  Constructing the truth table from a logic expression. (1) Determine the number of the input and output variables, and the number of the input variable possible combinations. (2) Draw the truth table frame according to the input and output variables