It has been a while since I used my scientific calculator. Most of my assignments and projects for a few semesters only require programming with a simple calculation. I never thought this semester I need to use my calculator again, especially for the logarithm calculation. I pressed the ON button and the screen displayed the cursor and a few modes on top. It takes a few seconds for me to recall back the function for each button. I pressed the log button and entered the value needed. Then, I pressed the SHIFT button, the top-left button and the screen displayed S on the top-left, indicating that I have pressed the particular button. After that, I pressed the fraction button and the screen displayed the improper fraction template. I entered the required value and pressed the equal button to get the answer. The screen then displayed the answer below the equation that I have made before. This case study can be related to one of the fundamental design principles which are Feedback.