Storage and DrRacket

         As usual, I find the hardware part of this course is harder for me than the operation of DrRacket. The lecture in this week is about hardware architecture. Our professor explained how different hardware saves data in their storage. I took some time to understand the load instruction by recalling the carry-in and carry-out principle in the previous class. However, I didn't really get the storage of hard drive. The only thing I got was the speed of hard drive is a major shortage compared to the other types of hardware. After class, I read over the extra notes online. It is helpful, and explains everything in a detailed way. 

         Regarding DrRacket, it is the second time to use the "cond" command. The first time was when the professor did the animation of clock in class. He used the "cond" command to define different keys of stopping the clock. I checked the file of the clock again in order to have a better understanding about how the "cond" command works. The "cond" command means that I can create some simple rules to let computers work with. So the computers can produce something particular or something else according to the rules.