1. CIS 199 Final Review

2. Classes Reference type Can only inherit from ONE base class
NOT a value type!
Can only inherit from ONE base class

3. Properties Class member
Holds a piece of data, information within an object
Accessors: get, set
Can use auto-implemented when validation is not required
If need validation, must create own backing field (instance variable) and write own get and set accessors
Read-only property – only has get, no set (no public set, at least)
Controllable scope

5. readonly Can make an instance variable readonly
Initial value will be established in constructor
After value is set, it may not change again

6. Inheritance Extend, Expand an existing class Specialization
Generalization
“All students are a person, but not all persons are a student”
Derived class “IS-A” base class
Student IS-A Person
Even if no base class is specified, one will be provided
Object
This is where method ToString was originally defined

9. Protected vs Private
What is the difference between Protected vs Private?

10. Protected vs Private
Private-The type or member can be accessed only by code in the same class
Protected -The type or member can be accessed only by code in the same class, or in a class that is derived from that class.

11. Polymorphism Complicated Concept
An object’s ability to take on, become different forms
Child classes take on properties of parent
Objects may be treated as base class
Students can be treated as a person
Keywords of note:
“override” – New implementation of a member in a child class that is inherited from base class
“virtual” – Class member that may be overridden in a child class
“abstract” – Missing or incomplete member implementation. MUST be implemented by child classes // More a 200 concept

12. Abstract Classes Generic class Provides some members, some information
CAN NOT be created directly
Meaning direct instantiation is illegal
Serves as a common “base” for related objects

14. Test 01 Material

15. Computer Hardware Central Processing Unit (CPU) Main Memory (RAM)
Brains
Operations performed here
Main Memory (RAM)
Scratchpad
Work area for programs, process, temporary data
Secondary Storage
Hard drive
Flash drive
CD, DVD

16. Input, Output Devices Input Output Takes data IN
Keyboard, Mouse, Game Controller, Microphone
Output
Pushes, places data OUT
Display, Speakers, Printers

17. Programs and Digital Data
Operating Systems. Microsoft Office, Web browsers
Instructions read by CPU and processed
Digital Data
1’s
0’s
…forms binary (base 2)

18. Built-In Types

19. Formatted Output Placeholders Letter codes – C, D, F, P Precision
Field width
Console.WriteLine(“x = {0,-10:F2}”, x);

20. Operators ++, -- int x = 5; int y; y = x++; vs y = ++x;
Postfix vs Prefix
int x = 5;
int y;
y = x++; vs y = ++x;
Shorthand operators
+=, -=
Integer division
1/2 == 0
1.0 / 2.0 == 0.5
10 / 3 == 3, 10 % 3 == 1
= vs ==

21. Properties Exposed “Variables” or accessible values of an object
Can have access controlled via scope modifiers
When thinking of properties: Values and definitions
“get” – Code to run before returning a value
“set” – Code to run before updating a value
Can be used for validation and other processing actions
“value” is a keyword in “set”

23. Methods Actions, code to be executed
May return a value, may take value (not required)
Can be controlled via scope keywords
Can be static
// Different example

24. Scope “private” – Can only be accessed by the class, object itself
“protected” – Can only be accessed by the class, object, or any child classes, objects
“public” – Available access for all

25. Named Constants AVOID MAGIC NUMBERS!
Allows for reference across similar scope
Change once, changes everywhere
// ALL CAPS

26. Conditional Logic if(expression) else if(expression) else
If ‘expression’ is true
If not true, skipped
else if(expression)
Can be used to ‘chain’ conditions
Code runs if ‘expression’ is true
else
Code to execute if ‘expression’ false
Statements can be nested

27. Relational Operators > Greater than < Less than
>= Greater than OR equal to
<= Less than OR equal to
== Equal to
!= NOT equal to
X > Y
X >= Y
X < Y
X <= Y
X == Y
X != Y

28. Operator Precedence (Highest) ++, --, ! * / % + -
< > <= >=
== !=
&& ||
= *= /= %= += -=
(Lowest)

29. Comparing Strings, Chars
You can use
==, !=
You cannot use
>, >=, <, <=
You SHOULD use:
String.Compare(s1, s2)
s1 > s2
Returns positive Number
s1 = s2
Returns zero
s1 < s2
Returns negative number
Compares the unicode value of EACH character

30. Test 02 Material

31. Basic GUI Example
Textboxes, labels, buttons, checkboxes, radiobuttons, panels, groupbox
Event handler

32. Loops for while do – while foreach
“For a given value X, while X is true, modify X…”
while
“While X is true…”
do – while
“Do these tasks, while X is true…”
foreach
“For every X in this set of Y do the following…”

33. for Example

34. while Example

35. do while Example

36. foreach Example

37. Key Loop Details Loops are NOT guaranteed to execute at least once!
…only exception is ‘do while’
Pretest vs posttest, or entry vs exit test
‘for’ loops require a variable, condition, and ‘step’ instruction
‘while’, ‘do while’ loops require a boolean expression
‘foreach’ loops require a collection of items
Arrays
Indefinite repetition – sequential search, sentinel control, validation loop

38. Nested loops
Output

39. Methods Actions, code to be executed
May return a value, may take value (not required)
Can be controlled via scope keywords
Can be static

40. Methods & Modularizing Your Code
Break out ‘steps’
Easier to test
Easier to visualize
Top Down Design

41. Arrays

42. Arrays

43. Sample Questions on Blackboard Wiki

44. What does ‘WYSIWYG’ stand for?
You
See Is
Get

45. What is the difference between a high-level and a low-level language?
Little to no ‘abstraction’ from the hardware or computer
“Close to the hardware”
Simple, but Difficult to use
Machine code, assembly, C (in some cases)
High-Level
Very strong ‘abstraction’ from the hardware or computer
“Far from the hardware”
Easier to use, abstraction adds complexity
C++, Java, C#, Python

46. How is the lifetime of a FIELD different from a lifetime of LOCAL variable?
Fields are members of their containing type
Fields can be used everywhere with appropriate scope
Local variables can be used only in their “local” environment

47. What two things does a variable declaration specify about a variable?
Type
Identifier
TYPE
IDENTIFIER

48. Describe ‘&&’ and ‘||’ and how they work.
Returns true if conditions are ALL true
“If you do well on the test AND the quiz, you will earn a great grade!”
|| (OR)
Returns true if ANY conditions are true
“You can run a mile OR walk two miles (possible do both!)”
Both short circuit

49. Why is ‘TryParse’ more effective than ‘Parse’?
Less code
No try / catch required

50. What is the difference between a SIGNED an UNSIGNED int?

51. What is the difference between syntax errors and logic errors?
Syntax Errors – Errors that prevent compilation or other factors that prevent successful compilation
string myString = string.Empty; // Won’t compile, syntax error
Logic Errors – Errors that occur during runtime, such as incorrect comparison or other unexpected behavior
If(grade > 60) { Code if grade is F } // Incorrect operator used

52. What are the “Five logical units”?
CPU – Processing, instructions
Memory – Scratch pad, working space (Temporary)
Secondary Storage – Hard drives, storage (Long term)
Input – Keyboards, Mice, Controllers
Output – Monitors, Speakers, Printers

53. Explicit type conversion? Why and how?
Variables must be used for a single type never change
Move from one type to another, must cast
EXPLICIT cast / type conversion
Aware of information loss

54. Write a code fragment that will display “Good Job” when int variable score is 80 or more, “OK” when score is 70 – 79, and “Needs Work” for any score under 70.

55. Write a code fragment that will apply a 10% discount to the value in double variable total when int variable numItems is 5 or more and int variable zone is 1, 3 or 5.

56. The ‘switch’ statement can replace nested if/else
The ‘switch’ statement can replace nested if/else. But under what conditions?
When matching on a specific…
Value
Type
Enumeration
…other data
Doesn’t work for floating point types

57. What does a ‘break’ statement do in a loop?
It stops (BREAKS) loop execution
Code continues, no further loop iterations
Example:
switch (comboBox1.SelectedItem.ToString()) {
case "A":
class_one_textBox = int.Parse(textBox1.Text); grade = 4.00 * class_one_textBox;
break;
case "A-": class_one_textBox =int.Parse(textBox1.Text); grade = 3.67 * class_one_textBox;

58. What does a ‘continue’ statement do in a loop?
Goes to the next iteration
CONTINUES loop execution, by skipping current iteration
This is only time a for loop would behave differently than a while loop

59. What are preconditions and postconditions for a method?
Conditions that MUST be TRUE before method execution
POSTCONDITIONS
Conditions that WILL be TRUE after method execution

60. What is the difference between a void method and a value-returning method?
Returns nothing!
…a void return.
Value-Returning
Returns a value!
…that’s not a void return.

61. Compare and contrast the use of pass by value against pass by reference, using key word ref versus pass by reference using keyword out.
Pass by Value
Passes a copy of the value
Not the object itself
Pass by Reference
Passes the actual object itself
‘ref’
Causes a pass by reference on a variable
‘out’
Is used to reference a variable that the method will update

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