CS50 2019 哈佛公开课 Lecture 0 Note

Computer Science

Lecture 0

1. How to speak the exponential notation

• for 10^3 in speaking English is ten to the three

2. bit byte transistor

• for binary 二进制 0, 1.

• 2 -> 10 4 ->100 8 ->1000 up to 8, it's called a bit

• 8 bits is called btye

• transistor 晶体管could control millons of switches to store values

3. ASCII Unicode

• for example, Character A is defined in the computer by using number 65, so switch to binary is (01000001). Different computers change this number to deliver their messages.

• Therefore, the world has ASCII /a:ski/ (American Standard Code for Information Interchange, 美国信息交换标准代码) use only 8

• Unicode like a superset (超集)of ASCII, more than 8, 16 and even 32 so on.

• for crying with a smile that face icon (emoji), in Unicode, the decimal number is 128514， change binary (1111101100000010)

• the computer user a series of binary digits to interchange information, like music, video, picture and so forth（means so on）， no matter what media we use to represent information, it all reduces to 0 and 1

4. Algorithms

• Algorithms(算法 ) are just step-by-step instructions for solving some problems.

• reusability (复用)

• computer thinking is important.