COP 2360 – C# Programming
Chapter 2 – Sept 2, 2015
Some Announcements
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Don’t forget all of the Powerpoints can be
found at:
–
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www.wodwhere.com/COP2360
November 11 is a holiday (Veteran’s Day – I
thought it was on Monday). So, the exam I
had scheduled for November 11 will be
rescheduled for November 4.
Computer System Basics

Computers are comprised of:
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Central Processing Unit(s)
Main Memory
Secondary Storage
Peripheral Devices
Central Processing Unit
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Is where all the “magic” happens
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But it isn’t really a lot of magic
It’s a little magic that happens very quickly
Basically, the only “things” that a CPU can actually do are:
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Move data from memory to a register, from a register to
memory or from a register to a register
Simple arithmetic
Logical comparisons (which is really done based on arithmetic)
Basic looping (which is really just setting the program counter
to a value, so is really included in “Things 1 and 2”)
Central Processing Unit
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The basis from many CPUs today is my old friend the 8080 processor.
In the “day” we had seven “free” 8 bit registers:
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A (the accumulator)
B and C (could act individually or as one 16 bit register)
D and E (also could act as two or one)
H and L (read above!! – Plus certain instructions allowed these two to be
used for a memory address called M)
We also have an 8 bit register called the “Flag” register that contains
specific bits for overflow, zero indicators and other stuff.
We also had a 16 bit Program Counter (that kept track of what
instruction we were on) and a 16 bit stack register, used to figure out
where to store stuff into memory.)
Central Processing Unit
Example Assembly/Machine Language
;
;
;
;
;
;
;
;
;
;
memcpy -Copy a block of memory from one location to another.
Entry registers
BC - Number of bytes to copy
DE - Address of source data block
HL - Address of target data block
Return registers
BC - Zero
1000
1000
1000
1001
1002
1003
1004
1005
1006
1007
1008
100B
78
B1
C8
1A
77
13
23
0B
C3 00 10
memcpy
loop
end
org
public
mov
ora
rz
ldax
mov
inx
inx
dcx
jmp
1000h
;Origin at 1000h
a,b
c
;Test BC,
;If BC = 0,
;Return
;Load A from (DE)
;Store A into (HL)
;Increment DE
;Increment HL
;Decrement BC
;Repeat the loop
d
m,a
d
h
b
loop
Central Processing Unit
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Today, there are a lot more instructions and registers
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The register size has been increased from 8 to 32 or 64
The CPU had been built to be able to combine simple math
and logic into more complex instructions
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by physically adding the pathways and gates to implement a
more complicated instruction
to have instructions that are made up of micro-instructions so
that a single machine language instruction is really many lower
level instructions
But the basics are the same. The damn thing can
only move stuff, and add stuff.
Central Processing Unit

Oh, did I mention it can do that stuff
10,000,000,000 times per second!!
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That’s 10 billion
So, it can’t do much, and it can’t do it to a lot,
but it can do a little to a little very, very
quickly!!
Main Memory
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Volatile electronic circuitry used to store programs and data for the
CPU to access and process against. Stored as a series of 1’s and 0’s
(or really, as whether or not a specific location in the memory is
positively or negatively charged.)
In the old days, data was directly read and written to main memory by
the CPU.
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Although main memory is fast, accessing main memory is about 100 times
slower than accessing the same information in a CPU register. (Which
meant that although the computer might be able to do 10,000,000,000
instructions per second, if it had to do stuff with memory, it was reduced to
only 100,000,000.
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Let’s be honest, back then we weren’t at 10,000,000,000 ips
Cache (expensive very fast storage) was introduced to help with this.
Basically, cache provides for almost register speed of access (if the data
the CPU wants is in cache).
Bottom line though, the CPU accesses information from Main Memory,
and the information must be in Main Memory for it to be able to
process.
CPU and Main Memory
A Pretty Picture
Secondary Storage
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Because currently Main Memory and Cache are volatile, they
loose their data when the system is turned off.
Also, although we have very large main memories available
now, they still do not come close to the total amount of data that
we are used to manipulating.
Secondary Storage (disc drives and solid state disks) allow
information from main memory to be permanently stored, but
with a catch.
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To access a single byte of information on a disk drive takes 10,000
ns (or basically is 10,000 times slower) than main memory access.
Here’s a picture of Storage Media
(If I had time, I would have put it to scale!!)
But then either tapes would have been way to big, or you would not
have been even to even see registers, cache or main memory
OK – Enough about hardware
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Let’s get into C# Programming
C# Basic Structure
usings (with semi-colon)
namespace FirstProgram
{
class FirstProgram
{
static void Main(string[] args)
{
//Do some stuff
}
}
}
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C# programs are collections of classes. Classes are comprised of Attributes, Properties and Methods.
One class is identified as the "Start Up Class" for the program
Main is a method that is usually always found in the start-up class for a program.
C# itself has really only simple math, assignment and logic statements actually included within the
language. Just about everything else is handled by class libraries that contain additional methods.
Each command in a C# program must end with a semi-colon
Let’s "Code" the Obligatory
Hello World program
// This is traditionally the first program written.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace HelloWorldProgram
{
class HelloWorld
{
static void Main(string[] args)
{
Console.WriteLine("What Up Dude!");
int nStop = Console.Read();
}
}
}
OK – That is out of the way
Let’s Move on
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All programming languages are really very
similar
–
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Once you understand how to design and
program, it becomes more of a translation
exercise.
But, you need to get the basics first….
Programming Language Basics
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A way to store and retrieve information to and from
memory.
A way to communicate with the "outside world"
A way to compute basic mathematics and store
results
A way to compare information and take action based
on the comparison
A way to iterate a process multiple times
A way to reuse components.
Variables
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A variable is a memory location whose contents may
change during program execution.
C# has two different "Types" of Variables
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Value Types – The variable represent a place in memory
that actually holds the value of the variable.
Reference Types – The variable represents a place in
memory that holds the ADDRESS of the value of the
variable.
Variables - A Pretty Picture
Value Variable Types
The variable location IS the value
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Integral Data Type
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int = Integer = 4 Bytes (+- 2 billion)
short = Integer = 2 Bytes (+- 32K)
long = Integer = 8 Bytes (64 bits) 16 digit precision
char = 16 bits (2 Bytes - Unicode) - Discuss
bool = Boolean (True/False) = (Not sure of length)
Floating Point Data Types
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Double precision (double) gives you 52 significant bits (15 digits), 11 bits of exponent,
and 1 sign bit. (5.0 × 10^−324 to 1.7 × 10^308. Default for literals)
Single precision (float) gives you 23 significant bits (7 digits), 8 bits of exponent, and 1
sign bit. 1.5 × 10^−45 to 3.4 × 10^38 with a precision of 7 digits. (Literals need to have
"F" appended)
WARNING WILL ROBINSON – Storing information as a Float will store an
approximation of the number, not potentially the correct number. Let’s see this in
action. Why do you think this is the case??
Value Variable Types
The variable location IS the value
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Decimal Types
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New – Up to 28 digits of precision (128 bits used to represent the number)
Decimal place can be included
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But unlike Float or Decimal, there is no conversion
The Precision and the Decimal place go together
For literals, put an “M” at the end to state that the number is a decimal
Unless you really need to use very very big number or very very small numbers, suggest you
use Decimal instead of Double of Float
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Boolean
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But you’ll still be responsible for understanding the different!!
Value of either true or false
You must use true or false, not 0, 1 or -1
Char
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Single Unicode Character (2 Bytes)
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What is Unicode??
In Assignment, Single Quotes are used
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Char bChar = ‘B’;
Reference Variable Types
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Remember, the Value of the variable is the
Address of the variable
–
Strings
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During Assignment – Double Quotes are Use
String sMyName = "Louis Bradley"
Objects (Classes)
A Word on Variable Types
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In C#
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All Variable Types are actually Classes
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Which implies that when you define a variable you are
really creating an Instance of an Class
We will go over this in excruciating detail next week.
Variable/Identifier Names
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Numbers, Letters (upper or lower case) and the underscore (_)
Must begin with either a letter or an underscore.
Cannot be a reserved word
Should be indicative of what the variable is storing
Capitalization Counts!!!
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Variable1, variable1 and VARIABLE1 are three different
variables!!!
Try not to use run on variable names
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costofliving – use cost_of_living or costOfLiving
currentinterestrate – use current_interest_rate or
currentInterestRate
Constants
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Constants are anything entered into a "C#" program
that cannot be changed.
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Named Constants are also unchangeable, but
instead of just being a number or string, they have a
name.
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Numbers, strings
Why would we want to do this?
Traditionally Named Constants are written in all
upper case. (Nothing is going to stop you from
mixed case. It’s just good practice!!)
Variable/Identifier Names
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So, what does this program do?:
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const double a = 2.54;
double y = 12;
double x;
x = y * a;
Variable/Identifier Names
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What about now?
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const double CENTIMETERS_PER_INCH = 2.54;
double centimeters = 12;
double inches;
inches = centimeters * CENTIMETERS_PER_INCH;
Comments and Structure
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Comments add readability to the code and explain what you are
trying to do
Single Line comments begin with two slashes
//this is a line comment
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Multi Line comments begin with /* and end with */
/*this is a multi-line comment
and this is line two of the comment */
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Program Structure relates to the use of white space and
indentation.
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Anything within a Curly Brace should be indented
Concepts should be separated with a blank link
Comments should explain what you are doing
Variable names should be indicative of what they are used for.
Reserved Words
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C# has a list of "words" that cannot be used
a variable or method/class names because
they are part of the "C#" language
Ones that we know about now include:
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int, float, double, char, const, void, string
to name a few
Arithmetic Operators
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+, -, /, * and % (Modulas/Remainder)
Exponentiation is a handled through method calls
/ with integral data will truncate the remainder
Standard order of precedence
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Parenthesis then
Unary operators (-) then
* / % from left to right then
+ - from left to right
Mixed Expressions
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If all operators are the same, then that data
type will be returned.
If one operator is floating point and the other
is integral, the integral is converted (cast) to
floating point and the expression evaluated.
This is done one expression at a time in
order or precedence.
Let’s do some for practice….
Mixed Expressions
What if you don’t like the rules
casting is a feature that can change the type of data so
that the calculation performs as you want, not as the
computer wants.
(int) (expression)
calculates the expression, then drops any digits to
the right of the decimal
(double) (expression)
calculates the expression, then stores whatever the
answer is in a floating point number
Casting a Char
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(int)‘A’ is 65 (the ASCII equivalent of the
symbol ‘A’
(char) 66 is ‘B’
String Type
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A string is a sequence of zero or more
characters.
Strings in C# are enclosed in double quotes
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char on the other hand are enclosed in single
quotes
The character number in a string starts with 0
and goes to the length of the string -1.
Spaces count!!
String Type Concatenation
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The "+" sign is used to combine strings into
longer strings
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sFirstName = "Louis";
sLastName = "Bradley";
sFullName = sFirstName + " " + sLastName
Syntax vs. Semantics
If the problem was to add five to two and then
multiple the sum by 3, which is correct?
int demo;
demo = 3 * 5 + 2;
demo = 3 * (5 + 2);
Assignment Statements
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The stuff on the right of the "=" is completely
computed, and then put into the memory
location on the left of the "=".
Initialization
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When a variable is declared, it is assigned a memory
location.
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That location probably already has stuff it in
A variable can be initialized in three different ways:
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At the same time it is declared
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In a separate assignment statement after it is declared
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int nNumber = 0;
int nNumber;
nNumber = 0;
It can be read from the console or from a file.
Displaying information to the Outside World
Console.Write/Console.WriteLine
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Simple format for a single variable:
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Also
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Console.WriteLine (Variable Name)
Console.WriteLine (Format String, Variable List)
Write and WriteLine do the same thing
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WriteLine includes a CRLF (Carriage Return/Line Feed) at
the end of the variables.
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We can do that with an "escape sequence" as well and we’ll
talk about that later!!
Format String Syntax
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The Format String is the first parameter to the
Write/WriteLine Method
It is a single string. Each set of curly brackets
represents the format of one variable (left most
variable is {0}, then {1}, etc.)
The string can also have regular text embedded
within in for context (similar to the C fprint command
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const int INCHES_PER_FOOT = 12;
int nFeet = 3;
int nInches = nFeet * INCHES_PER_FOOT;
Console.WriteLine ("{0} Feet = {1} Inches",nFeet,nInches);
Console Write Statement Examples
Formatting Output
Formatting Output (continued)
Formatting Output (continued)
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FYI. I never remember all of these codes. So, they
won’t be on the test, but the concept will be!!
There is also the ability to make up your own.
There is also a “width” indicate that goes after the
variable number
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Console.WriteLine(“{0,5:F0}{1,-8:C}”,9,14
The 9 will be right justified and five characters long, the 14
will be left justified, 8 characters long with dollar sign.
Escape Sequences
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\n = newline (same as endl)
\t = tab
\b = backspace
\r = return (no line feed)
\\ = just the backslash
\’ = print a single quote (otherwise thinks it is a char)
\" = print a double quote (otherwise thinks it is a string)
These are active on string assignment statements unless the
literal is preceded by an @:
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String sString1 = “This \t is \t a \t String”;
String sString2 = @” This \t is \t a \t String”;
Reading information in from the
outside world (Console.ReadLine())
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Reads a String from the console and puts it
into a String variable.
Once in the variable, parsing functions can
be applied to cast the string as something
else.
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String sInput = Console.ReadLine();
int nNumber = int.Parse(sInput);
Some Weird Stuff I Don’t Like
Increment and Decrement Operators

Pre-increment/decrement – before you do anything else, add
(or subtract) one from the variable
–
++variable --variable
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a = 5;
b = 2 + (++a);
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Post-increment/decrement – after everything else is done, add
(or subtract) one from the variable.
–
Variable++ variable-
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a = 5;
b = 2 + (a++);
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After the statement is execute, b = 8 and a = 6
After the statement is execute, b = 7 and a = 6
I Do Not Like This (Sam I Am) (except for one place we will get
into later!!)
Some More Weird Stuff I Don’t Like
Compound Assignment Statements
C# allows one to replace:
x = x + y;
with
x += y;
Can do similar crazy stuff with *, / and –
Let’s Not Do This!!
The book says it is concise.
I think it is confusing!!
And I’m passing out the grades
VS2012 Tutorial
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Creating Solutions
Projects in VS2012 = One Program
Adding Source Code
Compiling – Syntax Check
Running – Executable Location
Add another Project
Debugging Specific Project
Some Debugging Abilities
Let’s Write the “Paint Calculator”
Together
Assignment 1!!