cis 199 final review. new material structures value type not a reference type! used to...
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CIS 199 Final Review
New Material
Structures Value type
NOT a reference type!
Used to encapsulate small groups of related variables
Classes Reference type
NOT a value type!
Like a structure, but far more sophisticated, modern Can only inherit from ONE base class Can inherit from MANY interfaces
Properties Class member Holds a piece of data, information within an object Accessors: get, set, Controllable scope
Inheritance Extend, Expand an existing class Specialization Generalization “All students are a person, but not all persons are a student”
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
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
Test 01 Material
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
Input, Output Devices Input
Takes data IN Keyboard, Mouse, Game Controller, Microphone
Output Pushes, places data OUT Display, Speakers, Printers
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)
Built-In Types
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”
Methods Actions, code to be executed May return a value, may take value (not required) Can be controlled via scope keywords Can be static
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
Named Constants AVOID MAGIC NUMBERS! Allows for reference across similar scope Change once, changes everywhere
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
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
Operator Precedence (Highest) ++, --, ! * / % + - < > <= >= == != && || = *= /= %= += -= (Lowest)
Detailed from:http://msdn.microsoft.com/en-us/library/2bxt6kc4%28v=vs.100%29.aspx
Comparing Strings 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
Exceptions andException Handling Exceptions are…
“Exceptional” events Unexpected events, errors during runtime Unhandled exceptions? Stack trace and application death
Handled with try/catch/finally blocks Try block “attempts” to run the code in question Catch block handles the exception(s) that may occur Finally block, optional, always executes
Test 02 Material
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…”
for Example
while Example
do while Example
foreach Example
Key Loop Details Loops are NOT guaranteed to execute at least once!
…only exception is ‘do while’
‘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 Lists Generic Collections
Files OpenFileDialog
Used to load file from location
SaveFileDialog Used to select file save location
BOTH very User friendly!
OpenFileDialog
OpenFileDialog
SaveFileDialog
SaveFileDialog
Random Numbers in C# Provided from: System.Random Is ONLY pseudo-random
Produces a finite set of values with equal probability Not truly random, follows a mathematical algorithm
Created with OR without seed value Common methods used:
Next() Next(int) Next(int, int) NextDouble()
Creating and using aRandom Object
Usage & Expected Resultsof Random Methods
Methods Actions, code to be executed May return a value, may take value (not required) Can be controlled via scope keywords Can be static
Methods &Modularizing Your Code Methods
Break out ‘steps’ Easier to test Easier to visualize
Methods &Modularizing Your CodeExample
Arrays
Arrays
Sample Questions fromBlackboard Wiki
What does ‘WYSIWYG’ stand for? What You See Is What You Get
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
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
What two things does a variable declaration specify about a variable? Type Identifier
TYPE IDENTIFIER
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!)”
Why is ‘TryParse’ more effective than ‘Parse’?
Less code No try / catch required
What is the difference between a SIGNED an UNSIGNED int?
What is the difference between syntax errors and logic errors? Syntax Errors – Errors that prevent compilation or other
factors that prevent successful compilation striing 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
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
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
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.
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.
The ‘switch’ statement can replace nested if/else. But under what conditions? When matching on a specific…
Value Type Enumeration …other data
What does a ‘break’ statement do in a loop? It stops (BREAKS) loop execution Code continues, no further loop iterations
What does a ‘continue’ statement do in a loop? Goes to the next iteration CONTINUES loop execution, by skipping current iteration
What are preconditions and postconditions for a method? PRECONDITIONS
Conditions that MUST be TRUE before method execution
POSTCONDITIONS Conditions that WILL be TRUE after method execution
What is the difference between a void method and a value-returning method? VOID Method
Returns nothing! …a void return.
Value-Returning Returns a value! …that’s not a void return.
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
How can REACH further help you today? Ask Questions Now!
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