Unit2-05: Types of Errors

Learning Outcome

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

• A3.2 write subprograms (e.g., functions, procedures) that use parameter passing and appropriate variable scope (e.g., local, global), to perform tasks within programs.

• A4.1 demonstrate the ability to identify and correct syntax, logic, and run-time errors in computer programs; 

• A4.3 demonstrate the ability to interpret error messages displayed by programming tools (e.g., compiler, debugging tool), at different times during the software development process (e.g., writing, compilation, testing) ; 

• A4.4 use a tracing technique to understand pro - gram flow and to identify and correct logic and run-time errors in computer programs; 

• B1.1 use various problem-solving strategies (e.g., stepwise refinement, divide and conquer, working backwards, examples, extreme cases, tables and charts, trial and error) when solving different types of problems; 

• use local and global variables in a program

• find errors in a program and classify the type of error

Quiz Questions

With a pencil and paper, answer the following questions:

1. What does each of the following code output?
   a) print(10-2**3)
   
   b)print("{:.3f}".format(0.462519))

d) print("The remainder of 10/3 is {}.".format(10%3))

e) print ("8 - 4 / 2 = {}". format(8-4/2))

2. Explain the difference between a constant and a variable.

3. Declare a constant called "MAX_LIVES" as an integer with a value of 3 in Python and C++. Make sure to put a comment above the line.

4. Declare a variable called "username" as a string with a value of "Guest" in Python and C++. Make sure to put a comment above the line.

5. Why do we need test cases?

6. Create 1 test case for a program that calculates and displays the area of a triangle (Note: A = base * height / 2). Make sure to include units.

7. What is pseudocode?

8. Create the top-down design, flowchart and pseudocode for a program that asks the user for number of answers they got correct and the total questions asked. It then tells them the percentage they got on the test.

Review

• storyboard, top-down design, flowcharts & pseudocode

• variables vs constants

Lesson

• read "Python Local, Glocal and Nonlocal Variables"

  • watch the video within

  • what are global variables in Python?

    • global variables can be seen throughout the entire program

• go over setting breakpoints and stepping through a program with the debugger

• go over types of errors:

  • syntax error 

    • i.e. mispelling a variable name or function name inPython

    • i.e. forgetting a ";" at the end of a line in C++

  • logical error

    • i.e. calculating the "area" of a rectangle but your program states that it is displaying the "perimeter"

  • run-time error

    • i.e. dividing by 0 in your calculation, which will make your program crash

    • i.e. having an infinite loop in a program that never ends

• from the online book Computer Based Problem Solving by Patrick Coxall, read:

  • Scope of Variables

  • create the program in Python

Daily Assignment

• complete the Daily Assignment section in Hãpara Workspace for this day

  • if Hãpara is not working, make a copy of this document

  • move it to your IMH-ICS folder for this course

Extra

• recreate the program above in C++

  • set breakpoints and step through it with the debugger to understand what is happening