CIS 199 Test 01 Review - Resources for Academic
Download
Report
Transcript CIS 199 Test 01 Review - Resources for Academic
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 and
Exception 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 a
Random Object
Usage & Expected Results
of 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 Code
Example
Arrays
Arrays
Sample Questions from
Blackboard 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!
Need to see an Example?
Need to see a concept again?