Lecture 3: Control Flow and Error Handling

Question 1

What is the difference between usual approach and event driven computing?

Answer 1

Usual: Start > hits well defined branch and loop points>Demand user inputs at points>proceeds to end> stops
Event driven computing: Start> set up complete > enter a main loop> loop around waiting for events then triggering code when they occur.

Question 2

why use switch statements for flow control(3)?

Answer 2

• Simple, many frameworks allow you to write part of the code
• Switches are easy to extend
• Matching multiple events to one piece of code is easy

Question 3

StackOverflowException

Answer 3

the call stack cannot grow any larger

Question 4

OutOfMemoryException

Answer 4

the system has run out of memory

Question 5

NullReferenceException

Answer 5

when an attempt is made to access an attribute/operation of an object when the reference is set to null

Question 6

ArgumentException

Answer 6

one or more arguments were invalid

Question 7

FileNotFoundException

Answer 7

specified file does not exist

Question 8

InvalidCastException

Answer 8

a data type casting is not valid(usually because the types are unrelated)

Question 9

DivideByZeroException

Answer 9

attempt made to divide by zero

Question 10

IndexOutOfRangeException

Answer 10

array index is out of range

Question 11

OverflowException

Answer 11

converting a value, such as with the Convert object, results in a loss of data

Question 12

What are the Methods for error handling(2)?

Answer 12

Parse() and TryParse()

Question 13

What are Exceptions?

Answer 13

• when an error is detected an object is created with information about the error
• object is thrown directly to the error handling routine

Question 14

What are the three parts of a try catch finally block?

Answer 14

• try block contains code that may throw an exception
• catch blocks handle different exceptions that are thrown(0 or more)
• finally block executes the code regardless of exception or not

Question 15

Why use a Custom Exception?

Answer 15

often the exception classes will not be suitable so we create our own.