Unit #2-02

Learning Outcome

At the end of this lesson, you will be able to:

• understand what a variable is and how to use one

  • create an application that accepts input and saves it into a variable

• understand what a top-down design is and how to create one

Review

• review basic output and formatting

Lesson

• read Top-Down Design, from textbook Computer Based Problem Solving

  • and read Top Down Design in Programming, from textbook Computer Based Problem Solving

• go over what a Top-Down Design is

  • we use square line connectors and rectangular boxes

  • arrows always point down

  • normally left black & white

• go over how to create one using draw.io

  • the new,  easier way is to use VSCode and the Draw.io extension, right from GitHub!

    • just use the Codespace externsion

    •  or just type "period" (.), from any GitHub Repo to get into VSCode web version

  • to get your Top-Down Design into your Google Doc ALWAYS export it as a PNG file

    • the reason is that the resolution of the diagram is kept and even if you need to shrink it to fit nicely on the page, I can zoom in and still see all the text

    • File, Export As, PNG...

    • then insert it into your Google Doc

      • Insert, Image

    • ensure you then center, size and crop the image appropriately so it fits nicely on one (1) page

    • NEVER take a screenshot from Draw.io and paste that in!

• read Variables, from textbook Computer Based Problem Solving

• go over what a variable is

  • different naming conventions:

    • see "Different Naming Conventions" below: ↓

  • we will always use this rule, for Python:

    • lowercase with words separated by underscores as necessary to improve readability

    • ex: area_of_rectangle, time_of_day, number_of_students

  • this "=" IS NOT an equal sign, it is an assignment statement

• go over how to get input from a user

  • we need the "int" to convert the user input which is of "type" string to integer, since we can not do math with strings!

  • python:

    • # just start using a variable right away in Python
      length = int(input("Enter length of the rectangle (mm): "))

  • C

    • // declare the variable first in C
      int length;
      ...
      // then you can use it!
      printf("Enter length of the rectangle (mm): ");
      scanf("%d", &length);

    • NOTE: that we have used &length inside scanf(). It is because &length gets the address of length, and the value entered by the user is stored in that address.

Activity

• nill

Daily Assignment

• create a program that calculates the area and perimeter of a rectangle with dimensions entered by user and show the results to 2 decimal places (see terminal output below: ↓)

  • come up with three (3) test case, BEFORE YOU WRITE THE CODE to ensure you know what the answer should be BEFORE you start coding

    • then write the code and check to ensure your answers are correct!

Extra

• create the same above program in C

• we will always use this rule, for C:

  • lowercase to start, then uppercase, with words NOT separated to improve readability

  • ex: areaOfRectangle, timeOfDay, numberOfStudents

• at the moment we will use scanf to get input

  • I know this is a really bad idea, but we do not have enough skills yet to do it the correct way!