1. Tonga Institute of Higher Education
Debugging
Tonga Institute of Higher Education

2. Fixing Errors Bug – An error in a program
Debug - To find and remove errors (bugs) from a software program.
When an error occurs, try to understand the error
Try to fix the error yourself before asking for help.
If you ask for help, be able to describe what's going on
The more experience you have with errors, the better you will be able to fix them in the future

3. Compile Errors, Runtime Errors and Logical Errors
Compile Errors – Errors that are found during the compilation of a program
Your program is unable to compile
Runtime Errors – Errors that cause an abnormal termination of a program
Your program crashes
Logical Errors – Errors that are not found during the compilation of a program and do not cause an abnormal termination of the program
These are the most difficult to find and often results in very big problems.
You set an employees pay check to be $500,000 instead of $50,000

4. Common Compile Errors Parenthesis must occur in matching pairs
Error Message
')' expected.
A function must specify a return type
Option Strict On requires all function and property declarations to have an 'As' clause.

5. Common Compile Errors A function must return the correct type
Error Message
Option Strict On disallows implicit conversions from ‘<datatype>' to ‘<datatype>'.
A subroutine must not try to return something
'Return' statement in a Sub or a Set cannot return a value.
Creating an overloaded method with the same signature
Method ‘<MethodName>' has multiple definitions with identical signatures.

6. Common Runtime Errors Not provided a way for Loops to end
The program will run forever
A function must have a return value specified.
Null is returned
Dividing a number by 0
Trying to access a resource that is not available

7. Task List
Use the task list to quickly take you to the source of your error
This only works for compile errors
Double Click
on this to go
to the error

8. Break Points - 1 Helps keep track of the break points in your program
When the program finds a line with a break point, it will pause
Some lines of code cannot have breakpoints. (Example: Comments)
You can break on conditions. Right click on the break point for more options.
Example: Stop when a variable x = 15
Click here to set, disable
and remove breakpoints
Red highlight means a break
point is set

9. Break Points - 2 You can do many things while paused Examine variables
Step into a method
Step over a method
Step out of a method
Go back to the break point
Continue running the program
Step into
a function
Step over
a function
Step out of
a function
Go back to
break point
Continue
running the
program

10. Watch Points, Locals and Autos
Displays information about variables you select to examine
You must pick the information you need
There are 2 ways to add a watch point
Right click on a variable when the program is paused to add a watch point
Type in the variable name
Select the variable in the watch window and press the Delete button to remove it
When a variable changes, it turns red in the watch window
Locals / Autos
Displays information about different variables

11. Call Stack
Sometimes, we can become confused when we have many events and methods.
A call stack helps us remember how we arrived at a location
It lists the methods that were called to reach this point in code
We can change the information we see by right clicking in the call stack
We paused here
Shows how we got here

12. Output Shows output from your program
Useful for outputting lots of data when debugging a program
The output will not be seen by the user when the program is run
Use this code to print text in the output window
Debug.Writeline(“Output!”)