On March 31, 2009, Yansong Bai gave a speech at Yale University. He shared the Chinese dream behind his personal story with true feelings, and condensed the profound changes in china-us relations over the past four decades.
In his opening speech, Yansong Bai mentioned that the three presidents of the United States all graduated from Yale University, pointing out that Yale is a very excellent university. He also humorously said that the graduates’ qualities of Yale University are uneven. This interaction attracted audience’s attention. Next, Yansong Bai clearly stated the theme: my story and the Chinese dream behind it, creating a grand but not heavy atmosphere.
In 1968, Martin Luther King’s words “I have a dream” stood up all over the world. However, at that time, it was difficult for Chinese people to have their own dreams, because the problem of food and clothing had not been solved. With sincere, equal attitude and objective language, Yansong Bai clearly presents the life in China in 1968 to his audience. He mentioned the cultural revolution, saying he was put in a cowshed with his parents and his grandfather had to fight with the guards to deliver milk. He conveyed information in humor and expressed heavy topics in non-heavy language, so that the audience could understand the life of China at that time while laughing.
Later, by sincerely telling the story of what happened to him when he was ten, Yansong Bai brought the audience into the life of the poor family in 1978. In 1988, Yansong Bai passed the college entrance exam and came to Beijing. By mentioning American imperialism, Coca-Cola and Chinese medicine, as well as Michael Jackson, he provided a clear picture of the transformation of the relationship between China and the United States: the United States is no longer out of reach, but has become the details of life.
By mentioning “in 1998, when I was 30 years old, I had become a news program host of CCTV”, Yansong Bai naturally introduced his identity. He then referred to 2008 as the year when the American dream and the Chinese dream developed together. “I had my fortieth birthday during the Beijing Olympics. I was filled with emotion on that day, because when the time came to my birthday, I was broadcasting a wonderful game. Twenty-four hours later, when it’s time to go out of my birthday, I’m still on air. Then I realized the Chinese dream behind my story.” From the rapid development of China in the past 40 years, audience could understand the opportunity that the Chinese dream gives to every Chinese.
Throughout the whole article, Yansong Bai gave the speech with a sharing attitude. His full text focuses on his own personal experience as well as the difference and connection between the United States and China. While keep interacting with the audience, he also conveyed a lot of information about China. In addition, Yansong Bai always used the first person in his speech to emphasize his Chinese characteristics. The use of associated words is also a highlight of this speech. “But” “although” “not only” emphasize the logical relationship between sentences, magnify the effect of humor.
Computer systems are binary systems that use sequences of bits to represent data. A binary digit (bit) is the basic unit of information in computer systems and can have only two values: wither 1 or 0. Eight bits form a byte.
1 Byte = 8 bits
A bit is denoted by the small letter b, whereas a Byte is denoted by the capital letter B. Thus, 1B=8b.
>> decimal number system
The decimal number system is a positional system that uses ten digits (0,1,2,3,4,5,6,7,8,9,) to represent any number. The decimal number system (or base-10) has ten as its base and it is the most widely-used number system. Since base-10 is a positional system, the position of each digit within a number provides the multiplier by which that digit is multiplied.
Figure 1: Initial place values in the decimal number system (from CORE COMPUTER SCIENCE)
>> binary number system
The binary number system is a positional system that uses two digits (0 and 1) to represent any number.
Figure 2: initial place values in the binary number system (from CORE COMPUTER SCIENCE) Figure 3: convert decimal number into binary number (from CORE COMPUTER SCIENCE)
Two’s complement is the way most modern computers represent signed binary numbers. The main advantage of this representations is that addition, subtraction and multiplication are carried out easily. suppose we want to find -28 28 in an 8-bit register is 00011100. fist, we invert the digits, so all ones become zeros and all zeros become ones. We get 11100011. Then we add 1, and the output is 11100100. So this is -28 in two’s complement representation.
In binary system the radix point is used to separate the fractional from the whole part. Fixed point representation method is the method using 4 bits for the integer part and 4 bits for the fractional part.
The hexadecimal number system is a positional system that uses 16 digits (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E and F) to represent any number. Digits A to F represent quantities from 10 to 15, thus A=10, B=11, C=12,D=13.E=14,F=15.
II. Data representation
>>Integers
We can use one byte to represent 256 different integer numbers. This would allow us to represent all the unsigned positive integers from 0 to 255.
We can also use sign-and-magnitude number representation. The left-most bit is set to 0 for a positive number or 1 for a negative number. This allows for numbers -127 to +127 to be represented.
>>Characters
The American Standard Code for Information Interchange (ASCII) is a character-encoding scheme originally based on the English alphabet. ASCII uses 7 bits to represent each character, which means that it can achieve 128 different representations.
>>Colors
Monitors use pixels to display information and have a specific display resolution, such as 1024 x 768 has a width of 1024 pixels and a height of 768 pixels. One way to store color in pixels is the hexadecimal RGB color values. Each color value is represented by values from 00 to FF, so a six-digit hexadecimal number is need such as 70EF5A.
Figure 6: color representation (from CORE COMPUTER SCIENCE)
An operating system (OS) is a set of software that controls the computer’s hardware resources and provides services for computer programs. It is a very important part of a computer system since it acts as an intermediary between software applications and the computer hardware.
Figure 1: User, application, OS and hardware (from CORE COMPUTER SCIENCE)
In a computer system, a user would interact with an application that has been designed to meet the user’s need. This application would require an operating system in order to function. This operating system would allow the application to interact with the hardware of the computer system.
The main services that an operating system provides are listed below: > Peripheral communication > Memory management > Resource monitoring and multitasking > Networking > Disk access and data management > Security
Figure 2: Security (from CORE COMPUTER SCIENCE)
II. Software application
Application software are programs designed for the end-user that enable the completion of various tasks in order to increase productivity. The main software applications that may be installed on such computer system include: > Word processors > Spreadsheets > Database management systems > Web browsers > Email > Computer Aided Design (CAD) > Graphic processing software
Software applications typically include a graphical user interface (GUI) to allow the user to interact with them in a number of ways. A GUI includes components such as graphical icons and visual indicators, as well as toolbars, menus, and dialogue boxes. These allow the interaction between the user and the software application to be performed more smoothly.
> Toolbar A toolbar is a GUI element on which buttons, icons, menus, or other input or output elements are placed. > Menu A menu is a GUI element that displays a list of commands that can be chosen by the user to perform various functions. > Dialogue A dialogue box is a GUI element that is used to communicate information to the user and allow him/her to respond by choosing an option form a list of specific choices.
Figure 4: A dialogue box (from CORE COMPUTER SCIENCE)
Software applications have improved greatly over the years. Early software applications operated with commands that had to be typed in, which we call command line interfaces (CLIs). Later ones took advantage of GUIs.
Figure 5: Pros and Cons of CLIs and GUIs (from CORE COMPUTER SCIENCE)
Secondary memory (a.k.a. secondary or auxiliary storage) is a relatively slow memory that may be written to but is also non-volatile. What’s more, secondary memory has a relatively high capacity to hold data compared to the primary memory.
Figure 1: CPU, primary and secondary memory ( from CORE COMPUTER SCIENCE)
When the computer stars-up the RAM is empty. Instructions and data need to be copied from secondary memory into the RAM in order for the computer system to run. This is very important since if secondary memory did not exist a computer system would be unable to store instructions and data persistently.
There are numbers of different secondary memory storage devices: > Hard drive (hard disk) > CD-RW, DVD-RW > USB Flash drive > SD (secure digital) or CF (compact flash) card > zip disk > Floppy disk > Magnetic tape
Figure 2: Hard drive (from CORE COMPUTER SCIENCE)
Figure 3: USB Flash drive ( from CORE COMPUTER SCIENCE)
Figure 4: A loaded DVD drive ( from CORE COMPUTER SCIENCE)
As secondary memory is obviously crucial to computer systems, it becomes apparent that advances in the technology surrounding secondary memory are beneficial to computer system as a whole. New technologies and existing ones strive to become more efficient, robust, and faster, as well as to hold more data than before.
I.The central processing unit (CPU) and its elements
Computer systems follow the concept of the input, process, output and storage model.
Figure 1: The input, process and output model (from CORE COMPUTER SCIENCE)
Data or instructions are processed by the central processing unit (CPU), which is a hardware component of a computer system and can perform basic arithmetic, logical or input/output operations, in order to process data from input devices into useful information. The CPU is the brain of a computer system and can process data very quickly, but it cannot think for itself (it can only process data by following instructions).
The CPU contains: > control unit (CU) > arithmetic logic unit (ALU) > memory address register (MAR) > memory data register (MDR)
The CU controls the retrieval of instructions from the primary memory as well as the sequence of their execution. The ALU performs all the basic arithmetic, logical or input/output operations. The MAR holds the memory address of the data to be used in ALU, so that ALU can fetch the corresponding content from the memory. The MAR may also hold the memory address of where data will need to be stored. In order for the MAR to communicate with the primary memory, a connection is necessary (Memory (Address) Bus). The MDR holds the data that is to be used by the ALU and then saved to the RAM.
Figure 2: CPU block diagram ( from CORE COMPUTER SCIENCE)
II. The RAM and ROM
The primary memory is the only storage that is directly accessible by the CPU. The primary memory consist of two types of memory:
Random Access Memory (RAM)is a general-purpose storage area, so the data stored can be over-written. However, RAM is volatile, which means that whenever power is lost the contents of its memory are wiped clean.
On the other hand, Read Only Memory (ROM) is used to store instructions and data that cannot be over-written, and it is considered non-volatile. ROM is much smaller than RAM.
III. The cache memory
RAM has two main types: >Dynamic RAM (DRAM) >Static RAM (SRAM) SRAM is faster but more expensive than DRAM, and as such DRAM is preferred for the main RAM. However, a small amount of SRAM is placed between the main RAM and the processor and it is called cache. Cache holds the information from the RAM that is most actively used, and accessed most frequently. The computer system will run faster as the slower main memory will need to be accessed less frequently. There are two types of cache. L1 cache is placed on the microprocessor itself whereas L2 cache is placed between the primary memory and the microprocessor.
IV. The machine instruction cycle
fetch instruction from primary memory to control unit
My first month in grade 11 was great. We studied topic 2 (computer organization) in CORE COMPUTER SCIENCE, which was really interesting. I became more clear about how computers work. Here are the five main areas we have learned:
Last few weeks we finished our flowchart poster presentation and learnt a lot about software. We leant its hierarchy, we defined it, and we leant different types of software (mainly categorize to system software and application software). Some interesting activities were done, too: watching videos about library softwares and translators, and in pair discussing about utility software. I heard a lot about software before but I do not know its true meaning until I finished these classes. I found software pretty interesting!
Flowchart poster
We were divided into pairs randomly to create a scenario using flowchart and pseudocode. I was with Adam and our scenario is about how to review for final exam. It is a really easy algorithm and is very useful, as it can be used not only for this semester’s final exam, but also for future final exams.
In our algorithm, we ask the user to input today’s date, which we recorded as BEG, and we ask when is the exam, recorded as END. Also there is an output “how many subject you need to prepare?” , and the input is NUM. Then we will calculate the day for one subject, using end-beg/num. For example, the beg is May 20 and the end is June 15th, and you need to review 8 subjects. It is 26/8=3. Then we created a loop to determine the review order. After that it goes to the second round of review.
The core idea of our algorithm is that we have two round of review and we review our most difficult subject first. So it let us to have much subjectivity. No matter how many days are remain and no matter how many subjects you have to prepare, you can use this algorithm to get a plan. Also, this algorithm is pretty simple and doesn’t get into details, because we all know that less is more. We don’t need to spend hours to elaborate a perfect detailed plan.
Software
layers of a computing system
First, from the view of layers, we learnt that programming, operating systems, and applications layers are softwares.
software hierarchy
system software
System software is a software designed to operate the computer hardware and to provide a platform for running application software. It contains system management program and developing software.
system management program: First, it is operating systems, a set of programs that make computer hardware conveniently available to the user. It hides the complexities of the computer’s operation in order to not disturb the user. For example, ios, apple, linux, and windows are all operating systems.
IOS
Second, library programs are also important. It is a set of commpiled routines that other programs can use. Comouter game developers often use graphical libraries to speed up development. We also watched a video about it, and I’m very surprised that designing a computer game include so many steps. We need to create characters( how they look like, how they perform the action and their voices), backgrounds (colors and textures), and story line. Abstract and concrete thinking are involved. After that we need to conduct experiments to find and repair bugs. It can also apply to our daily lives: after we finished our prorams/homeworks/anything, we need to examine it carefully.
Utility softwares are programs that perform a very specific task related to working with computers. They are tiny but powerful programs with a limited capability, and are used to maintain a smooth running of the computer system. I discussed 7-zip with Mr. Shao and we thought it is an untility software. After everybody shared their examples (include virus scanner, desk cleaner, and file managers), I found that 7-zip is an overlap, for it has some specific purposes, too.
Developing software: The most important one is translator software. It is a software that allows new programs to be written and run on computers, by converting source code (java/python/C++) into machine code (binary language).
There are three types: Assembler is a program that translates low level programming language into machine code. We watched an interesitng video to see the difference between compiler and interpreter: Compiler is a program that takes a program in a high-level language and translates it into object code all at once. It is pretty fast and some apps on our phones use it. Interpreter analyses and executes a high-level language program line by line, so it is easy for us to correct mistakes. “Inter” means between the programs and the mechanics.
application software
Application software allows users to perform non-computer tasks. It is a software designed to help the user to perform specific tasks, such as writing a letter or processing orders. It can be further divided into:
General purpose application software
General-purpose software is a type of software that can be used for many different tasks. It is not limited to one particular function. For example: word processors allow us to write articles, make poster, and create tables.
use word to take notes
Special purpose application software
It is a type of software that created to execute one specific task. For example: A camera application on your phone will only allow you to take and share pictures. A chess game would only allow you to play chess.
Bespoke application software
Bespoke software is tailor made for a specific user and purpose. It is the opposite to “off the shelf” (for regular people). For example: BNDS may want a software for students to give their suggestions. Since the software need to consider the conditions in BNDS, it would have to be specially built for the task. Other examples: software for the military operations, software for hospitals and software for banks.
We learn different types of softwares in this week, and for each type we not only defined it but also give specific examples to better understand it. We watched video and discussed in pairs. It is a little bit difficult since we need to memory and distinguish these softwares, but by doing these we can immprove our abstract and concrete skills (there are big and small categories).
Last few weeks we learnt a lot about algorithm. We defined it, leant its properties and studied how to design an algorithm. Some interesting activities were done, too: role playing, magic show, route planning and robot game. I found algorithm so common and important, but it is a little bit difficult for me to memorizing so much things.
Some Basic Information
The first question is obvious: what is an algorithm? After some discussion, we got a perfect definition of it: a set of step-by-step clear instructions to solve a problem in a definite amount of time with the best effeiciency possible.
Then, by sharing some examples, we found out that algorithm has five properties. First, finiteness is important. That means an algorithm must end in a finite number of steps, because we can’t wait for years. Second, definiteness: each step of an algorithm must be precisely defined, so the computer can operate the same way as you expect. What’s more, an algorithm must has input and output. Finally, all of the operations in the algorithm need to be basic enough, so the computer can understand it. Also, people want to save time and space, so algorithms are always very “clever”, that it use the best way to solve a problem. That property is called effectiveness.
ALgorithem is also a critical part of computational thinking, which include decomposition, abstraction, pattern recognition and algorithm.
Algorithem Magic
We were divided into four groups to conduct four magic shows about algorithm. I was with Tiger, Lucy, Elizabeth and Adam, doing Australian Magician’s Dream. Unfortunately, we did the same show as group two. It really gave us a lesson: we should check before we start. Also, I found that gourp two’s presentation involved computational thinking, which I didn’t think about. They related decomposition and abstraction with the magic. I thought we both did a great job.
This trick is about finding the 16th card, and all we did is divide them into two piles and repeat the process. When group two was explaining, one of them said the total number of the cards chosen should be less than thiry-two. I didn’t think so, because if a magic show has so many uncertainties, it can not be called a magic show. Smart magician can handle situations, for example, if it is more than thirty-two, we can change the card we pick, that’s all.
My part was to expain the link to computer science. The magic show is the exact algorithm for computers to find data. I used sixteen cards which all have binary numbers written at the top, and some holes indicating their numbers. If we want to find sixteen, which is 10000 in binary, we can just use a toothpick respectively pass through the last four zeroes. After the first round, all the odd number cards go, because I shake out all the cards that have one as last number in binary. We keep that and finally only number sixteen remain.
Other groups showed us The Intelligent Piece Of Paper and The Red Black Mind Meld. When Jerry was explaining different situations of the game, I thought he was wrong so I interupped him. But after his explaination, I realized I was wrong. At that moment I was a little embarrased, for I thought I’m not very polite and I’m stupid. I should think deeper before asking. But I also think I gain more by asking this question, for I realized a blind point of my logical deduction.
Other Interesting Activities
Video
We watched an really beneficial video-“The Secret Rules of Modern Living: Algorithms“. I’m very surprised that algorithm is everywhere. It is not just a term in computer science, it hinds quietly behind all things and rules our lives. An intersting example of it is a mathematical game, in which there are thirty cards in a box and two players who can only take away 1-3 cards at once. In order to win the game, the beginning person can just take away two cards, and then every round make sure the sum of the card took away is equal to four, so after seven rounds the person will win. Another example is a mathcing algorithm which can apply to marriage assigning, college admission, roomates choosing and so on. As for college admission, the first step is that all students propose their dream school and then the school reject extra students whom they like least according to their principles. After enough rounds there will be a stable outcome.
We did a homework about designing the route for a robot to light the squares. The game is on lightbot.com/flash.html. At first, it is pretty easy. Decomposition is really impoortant in designing the route, for we need to light the square one by one so we need to split the problem into small pieces. Then, in order to be more efficient, we are asked to repeat some procudures.
This is a very difficult one
I think smart repetition can also save our time and energy in daily life. For instance, I want to improve my English. Instead of read a short paragraph one day and listen to English songs another day, which require me to think what to do everyday, I can just read an English book. Everyday I can read one chapter and then read it aloud to practice my speaking, so I can get used to it and thus can follow this perfect plan everyday.
Design An Algorithm
We also leant how to design an algorithm. There are two main areas to look at: the big picture (what is the final goal?) and the individual stages (what barriers need to be overcome on the way?)
Understanding the problem is important. We can ask ourselves some questions to help check if we understand the problem thoroughly. For instance: What are the inputs(what do I alrealy have) and outputs(what result do I want) of this problem? What do I need more? What decisions need to be made in the problem? Are any areas of the problem repeated? In what order do instructions need to be carried out? Take brushing teeth as an example. If you do not conduct it in the right order, which means you brush your teeth before putting toothpast on your toothbrush, the effect will not be as good as that of a right order.
Then, we learn four expressions of algorithm. First, it is Natural Language. It means simple english and is always too verbose and ambiguous. Flow Chart, a formalized graphic representation, is another expression of algorithm. Pseudocode is another form. It is a generic artificial language, and has some naming conventions. For example, while means a loop, variable names are all capital, and == means compare. Finally, programming language is also useful. It is an artificial language to communicate with computer system.
An example of flow chart
The magic and wisdom behind algorithm really fancinates me, and I’m a little overwhelmed with so many things: definition, properties, examples, designing and expressions. Really looking forward to new cs knowledge and intriguing class activities!
This week we’ve learnt a lot: what is a binary number system, how does a computer work, as well as ASCII and unicode. Things get more complicated and more innteresting, and we also did some activities to better illustrate these abstract concepts about computers.
Binary number system
First, we learnt binary number system. Computer converts data, which is stored and transmitted as a series of zeros and ones, into information.
I wondered why we only let computers using zeros and ones, for the binary number system need more space than decimalism. By searching on internet, I understood that binary system is easy to achive, since we can let “close the circuit” to be zero and “break the circuit” to be one. What’s more, it is easy to calculate.
So how to convert decimal to binary? First, split the number into the sum of the power of 2. For example, 7=2^2+2^1+2^0. Second, find the length of the binary number. The length is the biggest power plus one. In this case, it’s 2+1=3. Finally, fill the space: fill one on each power+1’s space (counting from right) and then fill the remain space zero. So 7=111. If we want to convert binary to decimal, just plus each 2^(place-1) for every place that contains one. For instance, 111=2^0+2^1+2^2+7.
That’s interesting! We also had an activity that five volunteers respectively represented 1, 2, 4, 8, and 16. We counted from 1 to 31 by combinding these numbers. I found the idea of “combinding/rearranging things we already have to form new things/to convey information” really interesting and useful. In our life, for instance, we use English which have only 26 letters. It is so helpful, just because we arrange letters in different ways! We also did a worksheet to practice our skills.
How does a computer work
In order to understand how does a computer work, we fist looked at some important terms: CPU, CU, ALU, Register, and Bus. CPU, the central processing unit, is like the brain of a computer. It is where computers execute instructions form memory. Basically there are four parts in the CPU: CU, ALU, Register and Bus. As for CU, control unit, it makes decisions and sends signals to other parts of the computer. Arithmetic Logic Unit (ALU) is the place to do calculations and it can also deals with logic. Register can store information temporarily. Bus‘s function is to carry information to other parts of the CPU.
Then we watched a cute video in which we all became “electrons” and had a wonderful tour inside of the computer. We surprisingly known that there are so many steps between a click and the final display. Sometimes we ignore and despise little things like these and consider them as “very easy stuff”, but only if we do it oulselves we can find out the truth.
So here is my understanding of how does a computer work: When the computer receives instruction (input) from the user, the CPU begins to execute these information at once. CU get information from memory and send them to ALU and register through bus. Bus also carries infromation from CU to display. Finally we can get our output shown in display.
We were also divided into groups to experience this, and our group got a strange pattern (it is supposed to be a heart). The error may occur in any of us: CU(me), ALU(Hania), display(Catherine), and I realized in a team we need everybody perform well, otherwise we can’t get a good result.
ASCII and UNICODE
ASCII, American Standard Code for Information Interchange, is a standard that assigns letters, numbers,and other characters in the 256 slots available in the 8-bit code. For example, lowercase i would be represented in the ASCII encoding by binary 01101001.
Unicode is a standard for the consistent encoding, representation, and handling of text expressed in most of the world’s writing systems.
There are many differences between them:
• Unicode is an expedition of Unicode Consortium to encode every possible languages but ASCII only used for frequent American English encoding. For example, ASCII does not use symbol of pound or umlaut.
• Unicode require more space than ASCII.
• ASCII only supports 256 characters while Unicode supports much more characters.
In conclusion, this week we had a glimpse at the inside of our computers: we learnt their language (binary system), how they work and some smart ways letting they work (ASCII and unicode). I had a feeling that some of the students really known a lot about computers and I’m very new to it. Nevermind, I’m sure I will get more fimiliar with my friend–Mr. Computer!
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