CIS 199 Final Review

1. CIS 199 Final Review

2. Classes • Reference type • 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) • 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 • Takes data IN • Keyboard, Mouse, Game Controller, Microphone • Output • Pushes, places data OUT • Display, Speakers, Printers

17. Programs and Digital Data • Programs • 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 • ++, -- • 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) • 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 • “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 • Methods • Break out ‘steps’ • Easier to test • Easier to visualize • Top Down Design

41. Arrays

42. Arrays

43. Sample Questions onBlackboard Wiki

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

45. What is the difference between a high-level and a low-level language? • Low-Level • 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. • && (AND) • 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?