Computing

Week 1 notes

• Line of Code: A single instruction for the computer to perform.
• Program: An independent collection of lines of code that serves one or more overall functions.
• Input: Data that is fed into a program for it to operate upon.
• Output: What the computer provides in return after running some lines of code.
• Compile: To translate human-readable computer code into instructions the computer can execute. In the programming flow, this functions as a check on the code the user has written to make sure it makes sense to the computer.
  • 不能保证最后结果的正确
  • 分为静态（编译类）和动态（解释类）
• Execution: Running some code and having it actually perform its operations.

• 语言只是前置，了解 computing 的内在联系才是关键

• 所有的内容都是 text

• an output medium that uses more than just text, like forms, buttons, tabs, and more. More programs are graphical user interfaces.

• Computing 指如何 Programming

• Variables
• Functions
• Reserved words
• Input / Output

• High level
  • 更远离底层
  • 更少的依赖平台和操作系统
• Interpreted

• Programming: Writing code through an iterative process of writing lines of code, attempting to execute them, and evaluating the results.

• 一行代码代表一个指令
• 任务可以分解成不同的指令

• code 应该尽量以小单位来组织

• print()，function,自带换行
• python 区分大小写

• Static:
  • the entire program is compiled before it is run
  • prechecking the code for errors
• Dynamic: the lines of code are compiled and run one at a time.

• 像计算器一样工作
• 用于快速测试，获取结果
• intercative mode 下，所有内容都会自动打印

• errors
• incorrect results

• 解决程序出现的 error 或是 incorrect results 的问题

1. 获取足够多的信息
2. 定位问题所在
3. 解决问题

• error 分为：
  • compilation error : Errors that occur during the computer’s read through of the code.
    • syntax errors: 语法错误
    • Name errors: name 不存在
    • Type errors: 类型不匹配
  • runtime error: Errors that arise when trying to actually execute the code.
    • Divide by zero
    • Null errors: name exists but no value
    • Memory Errors: code that surpasses your memory

• NameError:An error that usually occurs when you use a variable name that doesn't yet exist
• TypeError: An error that occurs when we try to perform an operation on an object that doesn't make sense with the operation
• AttributeError:An error occurs when we ask for information about a variable that doesn't make sense, like the happiness of a potato or the GPA of a turnip.
• SyntaxError:An error that occurs when the line of code we've written can't be read by the computer because it doesn't match the computer's expectation for the programming language's grammar.

• Print Debugging：打印信息用于跟踪
• Scope Debugging：缩小跟踪的范围，特别是 variable 在不同时期的状态变化
• Rubber Duck Debugging：自己解释程序的逻辑，目标等，在解释的过程中找出 bug 的存在。

• 在 loop 开始和结束的地方添加开始和完成的信息。
• 通过打印的信息可以确定问题出在第二个 loop。

• 首先确认不是次数的问题
• 其次将累加 loop 的的范围减少为 2 次来查看是否出现了累加的问题

I call this “scope debugging” because the goal is to debug small scopes of your program, rather than trying to debug everything all at once. If you have a 20-line program, for example, you might break it down into four 5-line chunks and say, “Ok, the program has worked through the first five lines, but it breaks in the second five lines…”