Ref:

• “Introduction to Computation and Programming using Python” by Guttag.

• MIT OCW pages. Links: Link, Link.

ROUGH NOTES (!)
Updated: 27/4/26

INTRO TO CS AND PROGRAMMING WITH PYTHON

Lec-1

Link to the lecture: Link.

[Types of Knowledge]

• Declarative knowledge is statements of fact.
• Imperative knowledge is a recipe or “how-to”.

Programming is about writing recipes to generate facts.

[Numerical Example]

Square root of a number x is y such that y * y = x.

• Start with a guess g.
• If g * g is close enough to x, stop and say g is the answer.
• Otherwise make a new guess by averaging g and x/g.
• Using the new guess, repeat the process until close enough.

Why does it work?

Here is a pic:

[We have an ALGORITHM]

Checklist for an algorithm:

• Sequence of simple steps.
• Flow of control process that specifies when each step is executed.
• A means of determining when to stop.

Algorithms = Recipes.

[Computers are machines that execute algorithms]

Two things computers do:

• Performs simple operations (100s of billions per second)
• Remembers results (100s of gigabytes of storage)

What kinds of calculations?

• Built in to the machine, eg, +
• Ones that you define as the programmer

A computer will only do what you tell it to do.

[Computers are machines that execute algorithms]

Fixed program computer

• Fixed set of algorithms
• What we had until 1940s

Stored program computer

• Machine stores and executes instructions

Programs are no different from other kinds of data.

[Stored program computer]

The Stored program computer has:

• Sequence of instructions stored inside computer
  • Built from predefined set of primitive instructions: Arithmetic and logical, Simple tests, Moving data.
• Special program (interpreter) executes each instruction in order.
  • Use tests to change flow of control through sequence
  • Stops when it runs out of instructions or executes a halt instruction

Look at slides 17 to 24 here. Link to the slides: Link.

[Basic Primitives]

Turing showed that you can compute anything with a very simple machine with only 6 primitives: left, right, print, scan, erase, no op.

Real programming languages have:

• More convenient set of primitives
• Ways to combine primitives to create new primitives

Anything computable in one language is computable in any other programming language.

[Aspects of Languages]

Primitive constructs: (Analogy)

• English: words
• Programming language: numbers, strings, simple operators

Syntax: (Analogy)

• English: "cat dog boy" is not syntactically valid. "cat hugs boy" is syntactically valid.
• Programming language: "hi"5 is not syntactically valid. "hi"*5 is syntactically valid. (We have object operator object)

Static semantics: which syntactically valid strings have meaning

• English: "I are hungry" is syntactically valid but has static semantic error.
• PL: "hi"+5 is syntactically valid but has static semantic error. (Not valid even though we have object operator object.)

(To do: Syntax and Static Semantics)

[Aspects of Languages]

Semantics: the meaning associated with a syntactically correct string of symbols with no static semantic errors

English: can have many meanings. For eg, "The chicken is ready to eat."

Programs have only one meaning. (But the meaning may not be what programmer intended).