Introduction 1. programming language
Low-level language: -------- internal computer machine language only accept binary code, it is represented by 1 or 0 instruction is referred to as machine instructions, machine instructions constituting entire machine language of the computer.
-------- assembly language machine language with substantially the same, are operating directly on the hardware, but uses a command identifier abbreviation is easier to recognize and remember.
Advantages: lowest level language, fast.
Cons: too complex; the lowest development efficiency.
High-level language: the atmosphere by two types of conversion mode
---------- refers compiled class before performing the source application, source code will be "translated" into object code (machine language).
Advantages: does not require source code is executed when the program is not dependent language environment; fast execution.
Disadvantages: need to be recompiled every time you modify the source code; cross-platform poor.
---------- explained based application source code while "translated" by the corresponding language interpreter as object code (machine language), i.e. translate and execute.
Pros: good cross-platform; can be modified at any time.
Disadvantages: low operating efficiency; plaintext code.
Which, python is an interpreted language, want to run the code must be executed by an interpreter.
2. Variable
Definition: the intermediate results of the program operation is temporarily stored into memory, the code continues to prepare for call back.
Naming rules:
Variable names can only be arbitrary letters, numbers, underscores combination
Beginning of the first character can not be a number
Keywords can not declare variables
Which it noted that: generally considered all uppercase called constants.