• 들어가기 전에
  : 해당 강좌는 MIT 의 OpenCourseWare 수업을 듣고 내용을 정리한 것이다.
  : 강좌명은 Introduction To Computer Science And Programming In Python, 6.0001 이며 링크는 다음과 같다.
  https://ocw.mit.edu/courses/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/video_galleries/lecture-videos/

배울 내용

• 0. Course Info
• 1. What is computation?
• 2. python basics
• 3. mathmatical operations
• 4. python variables and types

0. Course info

Topics

1. Learning how to program
   • represent knowlege with data structures
   • iteration and recursion as computational metaphors
2. How do you write good code
   • abstraction of procedures and data types
   • organize and modularize systems using object classes and methods
3. Computer science
   • different classes of algorithms, searching and sorting
   • complexity of algorithms

1. What is computation?

What does a computer do?

1. Calculation
   : built-in
   : ones that you define

2. remembers results

3. only know what you tell them

Types of knowlege

• Declarative knowledge : fact
• Imperative knowledge : recipe or "how-to"

What is a recipe?

1. Sequence of simple steps
2. Flow of control
3. A means of determining when to stop

=> 1 + 2 + 3 = Algorithm

Stored Program Computer

• Sequence of instructions stroed inside computer
• Special program (interpreter) executes each instruction in order

Basic Primitives

• In computing, language primitives are the simplest elements available in a programming language. A primitive is the smallest 'unit of processing' available to a programmer of a given machine, or can be an atomic element of an expression in a language. (From Wiki)
• Turing showed that you can compute anything using 6 primitives (move left/right, read, write, scan, do nothing)
• anything computable in one language is computable in any other programming language

Aspects of languages

1. Primitive constructs

2. Syntax
   : Symbol 이 배치되는 구조나 형식

3. (Static) Semantics
   : Syntatically valid strings that have meaning
   : Syntax의 틀에 따라 작성된 언어를 이해하는 방법이나, 의미
   (https://jidoc.tistory.com/895)
   : 예를 들자면

   	3.2 * 5 // syntatically valid
   	3 + "hi" // static semantic error

4. Programming languages have only one meaning but may not be what programmer intended

Where things go wrong

• Syntatic errors
  : common and easily caught

• static semantic errors
  : cause unpredictable behavior

• no semantic errors but different meaning than what programmer intended
  : program crashes, stops running
  : program runs forever
  : program gives an answer but different than expected

2. Python Basics

Objects

• programs manipulate data objects (everything is object)
• objects have type
• scalar (cannot be subdivided) / non-scalar (have internal structure)

Scalar Objects

• int
• float
• bool (True / False)
• NoneType : special and has one value, None
• Can you type() to see teh type of an object

Type conversion

• can convert object of one type to another
• float(3) : integer 3 to float 3.0
• int(3.9) truncates (끝을 자른다) float 3.9 to integer 3

3. Mathmatical Operations

Operations on ints and floats

• i + j / i - j / i * j
  : if both are ints, result is int
  : if either or both are floats, result is float

• i / j
  : result is float

• i % j
  : remainder

• i ** j
  : i to the power of j (i^j)

4. Python variables and types

• type 은 위에서 서술.

Binding Variables and Values

• Equal sign is an assignment

  	pi = 3.14159

  : pi is variable, 3.14159 is value

  pi_approx = 22/7  

• Value stored in computer memory

• Assignment binds name to value

Changing Bindings

• can re-bind variable names using new assignment stastements

pi = 3.14
radius = 2.2
area = pi * (radius**2)
radius = radius + 1

# value of area is not changed

Abstracting Expressions

• Why give names to values of expression?
  : to reuse names instead of values
  : easier to change code later

번외 : Programming vs Math

• Math : solve for x
• Programming : you need to tell the computer exactly how to solve for problem