Chutong, Week 10

Computer at the beginning is just for calculating. The idea of “Augmenting Human Intellect” expanded the ability of computer as well as our understanding of what a machine can do. Now we have the information interaction between human and machine. And we can intuitively (based on physical perceptible images/sound/etc, and human symbolic cognition) understand these interactions through the interface. The inputs and outputs, the sockets, the screens are all parts of interface. 
The section on symbols in the reading reminds me of a website This is a website about the evolution of icons. We can see people use different images to interpret same meanings. 
Example: WeChat
WeChat’s logo is a very typical chat application logo. Compared with iMessage and WhatsApp, they all have this speech bubble (has a long history in inset and comics) inside. 
Understand the icons: 
The main page of WeChat is quite clear even you don’t read Chinese. The first logo below refers to message; second refers to contact list; third refers to exploration Moments (like twitter), this icon looks like a compass ( similarity: logo of Apple browser Safari ); and the forth is for profile setting. Understanding these icons are based on our previous experience and shared cognitive knowledge in our community. For example, why we can distinguish your own profile and contact list is because we usually use three or more lines as an image index of “list”, thus, we can quickly understand why they design the icon that way. 
How we sense all the elements on our screen:
Images that are visible to the human eye need the power of pixels to appear on the screen. Each pixel is made up of three colors, red, green and blue, which are arranged densely on the screen, presenting any graphics with different color values. The screen is made up of a number of pixels, each of which has red, green and blue filters (CRT) behind it. The filter filters the white light from the back of the screen, leaving a single color to pass through. The white light passes through three filters and is broken down into red, green and blue rays that enter the eye. Because a pixel is extremely small and the filters are so close together that when the light passing through them enters the human eye, we cannot distinguish the three beams of light. In other words, the light mixing in the human eye endow a pixel to “have” color.
A complete process from an input device to an interface display information to human eyes goes like this :(application/input device) data and instructions — >CPU — > graphics card driver — > graphics card — > display on your screen — > eyes.
Question 1: 
The reading about touch screen satisfied my curiosity of how touch screen works. Now I can understand why fingers can work well with touch screen while gloves can’t. But I still have questions about it. In a lot of experiments that I’ve done (as a Tap Tap Fish fan, I’ve done a lot of experiments with all kinds of touch-screen materials for saving my time), I’ve found that oranges work, pens don’t, although pen is conductive. And any conductive pointy shape things don’t work. Does this mean that the touchscreen sensor will also be affected by the stressed area? Can I regard this as “the orange on the screen has a large stressed area so it can effectively touch the screen, while the pen is too sharp so it can’t” ? If yes, why Apple Pencil works?
Question 2: 
People always say Apple has closed system, this term appears in the reading as well. And in the reading said the Macintosh PC is “the beginning of black-boxed, closed software systems” (Irvine, p.10). Could you explain more what is the closed system in computer science? Cause if I didn’t study this course, Microsoft PC is also a blackbox for me, for me it is also a closed box with mysteries. 
Crash Course Computer Science: Technical Background on PCs and GUI Interfaces