# Lecture 1 - What is computation ?

Computers does 2 things only:
- Calculate
- Remember Calculations

Computational problem solving & Computational complexities

From Ambigous problem statement to computational formulation of a method

Declarative vs Imperative Knowledge
Declarative: Like an axiom - Statement of Facts
Imperative: Like an algorithm - Sequence & Flow control - Computations

John Von Newmann & Alan Turing
Fixed program computer(Arithmetic logic Unit) - 1941 - Atanasoff & Berry
Manchester Mark 1 - University of Manchester
Stored program computer
Interpreter for instrutions - Now computers can program themselves

Flow control, Flowcharts
Programming Langs

Church-Turing Thesis - Defines the concept of Computability - The Nature of Computation
Lambda calculus - Computable and effectivelly calculable
if solvable by algo solvable by turing machine and vice versa
Universality of Computation

Halting problem - if you can prove a program will run forever or not ? no said Turing

Low lvl vs High lvl
Interpreted vs Compiled

Syntax, Static sementics (syntatical validity), Sementics(meaning)

Turing: We can compute anything using 6 primitives
Read, Write, Move Left, Move Right, Scan, Do nothing

Using Tape he showed can compute anything
modern langs evolved from primitives

primitives -> expressions -> values ->  meaning

Primitve constructs:
- English: Words
- Prog langs: Numbers, Strings, Simple operators

Static Sementics (Invalidity):
- English: I are hungry
- Prog langs: 3+"hi"

Sementics
- English: more than one meaning
- Prog langs: only one meaning

Everything in Python is an object:
- Scalar(int,float,bool(true/false),None)
- non-scalar(type())

<expr> = <var>

x % y = Remainder when x/y
x ** y = x to power of y

# Lecture 2 - Branching and Iteration