PRACTICES IN THE DESIGN OF HUMAN - COMPUTER INTERACTION: Human - Computer Interaction needs both mental and physical activities.The issues related to the motor actions, such as frequency-of-use, pace-of-interaction, type of interface, interaction style,type of instructions, step-by-step work,all-at-once work,etc.are termed as quantitative factors.On the other hand, the cognitive and perceptual actions associated with using the computer is related to the mental activities.The issues related to cognitive and perceptual actions,such as familiarity,fatigue,monotony,boredom,fear, anxiety,etc.are termed as qualitative factors.The quadratic assignment technique handles the qualitative and quantitative factors effectively in the objective function of the facilities layout problem.The techniques and tools of the quadratic assignment problems are found to be effective in the design of interactive systems for various types of users,viz.,expert,intermittent,and novice users.This work includes the proposed quadratic assignment models to design interactive systems that expected to be user friendly to increase the comfort and reduce the performance time for expert,intermittent&novice users.