NOC22 - CS42: An Introduction to Programming Through C++

• Notes and pointers for the NPTEL Course by Abhiram Ranade
• This repository will be in accordance with the run of January 2022 - April 2022

Week 1

Lecture 1: Introduction

• Computers are everywhere!
• Computer is defined as a giant electrical circuit that can receive data from external world, perform the calculations and send data to external world.
• Calculations depend on the program
• Program: a precise description of calculations we want the computer to perform
• C++: Developed by Bjarne Stroustrup in 1985, evolved out of C programming language
• Programming environment provided by SimpleCPP developed by IITB for beginners to programming
• The recommended textbook is written by the author of the course, Dr. Abhiram Ranade
• Introduction to C++ programs using SimpleCPP: Turtle Simulator inspired by the Logo software created by Seymour Pappert et al. to introduce children to programming.
• To run this program:
  • s++ <fileName>.cpp
  • ./a.out
• repeat statement: used to avoid redundant work by including the iterative work as the body of this statement. Each execution is called iteration. Syntax: repeat(x) { yyy }. The repeat statement causes the statements yyy in {} to be repeated x times.
• left(A): turn left A degrees. Equivalent to right(-A)
• sqrt(x): square root of x
• sine(x), cosine(x), tangent(x): x should be in degrees
• sin(x), cos(x), tan(x): x should be in radians
• penUp(), penDown(): Causes the pen to be raised, lowered; drawing happens only if the turtle moves while the pen is low
• cin and cout: used to accept input and produce output respectively
• Statement/command terminated by ;
• Commands are executed from top to bottom. and left to right
• Arguments: additional data needed by command to do its work
• Syntax: Grammatical rules indicating how commands must be written
• Comments: Ignored by compiler, read by people
  • /* This is a multiline comment */
  • // Single line comment until end of line
• Indentation: Spacing that allows human readers to read code more elegantly, if "X" inside "Y", then we give two spaces in before the start of "Y"
• Nested repeat statements:
  • repeat(x) { yyy } : execute yyy x times
  • If yyy contains repeat(w) { zzz }, then the zzz is executed w times in each execution of yyy
• Control is at statement w: Computer is currently executing statement w.
• Control flow: The order in which statements get executed. Generally, top to bottom, gets retraced if repeat statement.
• Variable: region of memory designated for storing some value you need.

Lecture 2: Problem Solving using Computer

• Modelling real life problems as mathematical problems on a high level overview basis

• Remember: Computers are for computations

• Computer Vision/Image Processing: Converting an black-white image into a sequence 0s and 1s

  • Grey scale: We denote each pixel using "grey"ness values of 0.1 to 1.0
  • Colored: We represent each pixel using red, blue and green component to obtain the required mix

• Weather prediction: Used to divide the surface of the earth into small regions. Each region is represented using pressure, temperature and humidity

• Language/text representation using numbers: Each character is mapped to a number. For example, a traditional system that is followed is the ASCII (American Standard Code for Information Interchange)

• Historical remark: Computers are used to solve problems, but problem solving is not new, humans have been solving numerical problems for millenia