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

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. First Program
  • 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. Draw polygon
  • 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