Special Topics 2

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Title: CS 112 Introduction to Programming, Fall 2003 Subject: Lecture 1: Introduction Author: Richard Yang Last modified by: DELL Created Date: 8/16/1999 2:47:17 PM – PowerPoint PPT presentation

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Title: Special Topics 2

1

Special Topics 2
C
Summer 2009
Luai M. Malhis, PH.D

2
Introduction

The course notes will be taken from many sources
on the internet
Other universities
From past courses at An-najah
From special sites dedicated to C
The complete set is not available
Course notes will be posted on the OCC

3
Introduction Continue

Course administration
Grading policy 20 First exam,
20 Second exam, , 20 Assignments , 40 Final
exam.
Text Book F. Scott Barker
Visual C 2005

4
C Library .NET Framework

Introduced by Microsoft (June 2000)
Vision for embracing the Internet in software
development
Language- and platform- independence
Visual Basic .NET, Visual C .NET, C and more
Includes Framework Class Library (FCL) for reuse
Executes programs by Common Language Runtime
(CLR)
Programs compiled to Microsoft Intermediate
Language (MSIL)
MSIL code translated into machine code
(Unlike Java) .NET is mostly Windows (MS) centric
There is a Linux port (e.g., the Mono project)

5
C the Language

Developed at Microsoft by Anders Hejlsberg et al.
Based on Java
event-driven, object-oriented, network-aware,
visual programming language
Incorporated into .NET platform
Web based applications can be distributed
Programs that can be accessed by anyone through
any device
Allows communicating with different computer
languages
Integrated Design Environment (IDE)
Makes programming and debugging fast and easy
Rapid Application Development (RAD)

6
C Continue

It is related to Java and C
Picking up Java after C should be easy.
It is simpler than other object-oriented
languages C
It is safe and robust --- no core dump or dead
console
It has good library and development support
good graphics package
good client-server and network support
It is good for your summer course
However, it is not easy to learn, with many
features

7
C Translation and Execution

The C compiler translates C source code (.cs
files) into a special representation called
Microsoft Intermediate Language (MSIL)
MSIL is not the machine language for any
traditional CPU, but a virtual machine
The Common Language Runtime (CLR) then interprets
the MSIL file
It uses a just-in-time compiler to translate from
MSIL format to machine code on the fly

8
C Compilation and Execution
C source code
9
The .NET Framework

Source code ? MSIL? machine language using
JIT
Common Language Runtime (CLR) Programs are
compiled into machine-specific instructions in
two steps
First, the program is compiled into Microsoft
Intermediate Language (MSIL) which is placed into
the application's executable file.
Using JIT (Just-in-time ) compiler which converts
MSIL to machine language, (JIT compile assemblies
into native binary that targets a specific
platform )

10
Setting the Path Environment

Assuming that windows and VS.NET2005 is
installed on the C drive on your computer, add
the following to the Environment Path
C\WINDOWS\Microsoft.NET\Framework\v2.0.50727
C\Program Files\Microsoft Visual Studio
8\SDK\v2.0\Bin
C\Program Files\Microsoft Visual Studio
8\VC\bin
C\Program Files\Common Files\MicrosoftShared\VS
A\8.0\VsaEnv

11
Compiling

The .NET Framework can be thought of as a VM
(virtual machine)
Save any C program in a text file
example1.cs, and set the environment variable
PATH to point to csc.exe compiler in the .NET
framework directory.
Go to the System Properties by right clicking
you? My Computer ? properties? Environment
variables? click on new? type path?C\WINDOWS\Micr
osoft.NET\Framework\v2.0.50727.
Now open the command console cmd and type
csc example1.cs.

12
A Simple C Program

//
//
//
// Classes HelloWorld
// --------------------
// This program prints a string called "Hello
World!
//
//
using System
class HelloWorld
static void Main(string args)
Console.WriteLine(Hello World!)

13
White Space and Comments

White Space
Includes spaces, newline characters, tabs,
blanklines
C programs should be formatted to enhance
readability, using consistent indentation!
Comments
Comments are ignored by the compiler used only
for human readers (i.e., inline documentation)
Two types of comments
Single-line comments use //
// this comment runs to the end of the line
Multi-lines comments use / /
/ this comment runs to the terminating
symbol, even across line breaks
/

14
Identifiers

Identifiers are the words that a programmer uses
in a program
An identifier can be made up of letters, digits,
and the underscore character
They cannot begin with a digit
C is case sensitive, therefore args and Args are
different identifiers
Sometimes we choose identifiers ourselves when
writing a program (such as HelloWorld)
Sometimes we are using another programmer's
code, so we use the identifiers that they chose
(such as WriteLine)

using System class HelloWorld static void
Main(string args)
Console.WriteLine(Hello World!)
15
Identifiers Keywords

Often we use special identifiers called keywords
that already have a predefined meaning in the
language
Example class
A keyword cannot be used in any other way

All C keywords are lowercase!
16
Namespaces

Partition the name space to avoid name conflict!
All .NET library code are organized using
namespaces!
By default, C code is contained in the global
namespace
To refer to code within a namespace, must use
qualified name (as in System.Console) or import
explicitly (as in using System )

using System class HelloWorld static void
Main(string args) Console.WriteLine(He
llo World!)
class HelloWorld static void Main(string
args) System.Console.WriteLine(Hello
World!)
17
C Program Structure

In the C programming language
A program is made up of one or more classes
A class contains one or more methods
A method contains program statements
These terms will be explored in detail throughout
the course

18
C Program Structure Class
// comments about the class
class HelloWorld

class header
class body
Comments can be added almost anywhere
19
C Classes

Each class name is an identifier
Can contain letters, digits, and underscores (_)
Cannot start with digits
Can start with the at symbol (_at_)
Convention Class names are capitalized, with
each additional English word capitalized as well
(e.g., MyFirstProgram )
Class bodies start with a left brace ()
Class bodies end with a right brace ()

20
C Program Structure Method
// comments about the class
class HelloWorld

Console.Write(Hello World!) Console.WriteLine(
This is from CS112!)
21
C Method and Statements

Methods
Building blocks of a program
The Main method
Each console or windows application must have
main method defined as static
All programs start by executing the Main method
Braces are used to start () and end () a method
Statements
Every statement must end in a semicolon

22
Console Application vs. Window Application

Console Application
No visual component
Only text input and output
Run under Command Prompt or DOS Prompt
Window Application
Forms with many different input and output types
Contains Graphical User Interfaces (GUI)
GUIs make the input and output more user
friendly!
Message boxes
Within the System.Windows.Forms namespace
Used to prompt or display information to the user

23
Syntax and Semantics

The syntax rules of a language define how we can
put symbols, reserved words, and identifiers
together to make a valid program
The semantics of a program statement define what
that statement means (its purpose or role in a
program)
A program that is syntactically correct is not
necessarily logically (semantically) correct
A program will always do what we tell it to do,
not what we meant to tell it to do

24
Errors

A program can have three types of errors
The compiler will find problems with syntax and
other basic issues (compile-time errors)
If compile-time errors exist, an executable
version of the program is not created
A problem can occur during program execution,
such as trying to divide by zero, which causes a
program to terminate abnormally (run-time errors)
A program may run, but produce incorrect results
(logical errors)

25
Constants

A constant is similar to a variable except that
it holds one value for its entire existence
The compiler will issue an error if you try to
change a constant
In C, we use the constant modifier to declare a
constant
constant int numberOfStudents 42
Why constants?
give names to otherwise unclear literal values
facilitate changes to the code
prevent inadvertent errors

26
C Data Types

There are 15 data types in C
Eight of them represent integers
byte, sbyte, short, ushort, int, uint, long,ulong
Two of them represent floating point numbers
float, double
One of them represents decimals
decimal
One of them represents boolean values
bool
One of them represents characters
char
One of them represents strings
string
One of them represents objects
object

27
Numeric Data Types

The difference between the various numeric types
is their size, and therefore the values they can
store

Range 0 - 255 -128 - 127 -32,768 - 32767 0 -
65537 -2,147,483,648 2,147,483,647 0
4,294,967,295 -9?1018 to 9?1018 0
1.8?1019 ?1.0?10-28 ?7.9?1028 with 28-29
significant digits ?1.5?10-45 ?3.4?1038 with 7
significant digits ?5.0?10-324 ?1.7?10308 with
15-16 significant digits
Type byte sbyte short ushort int uint long ulong
decimal float double
Storage 8 bits 8 bits 16 bits 16 bits 32 bits 32
bits 64 bits 64 bits 128 bits 32 bits 64 bits
Question you need a variable to represent world
population. Which type do you use?
28
Examples of Numeric Variables

int x 1
short y 10
float pi 3.14
float f2 9.81f
float f3 7E-02 // 0.07
double d1 7E-100
decimal microsoftStockPrice 28.38m

29
Boolean

A bool value represents a true or false condition
A boolean can also be used to represent any two
states, such as a light bulb being on or off
The reserved words true and false are the only
valid values for a boolean type
bool doAgain true

30
Characters

A char is a single character from the a character
set
A character set is an ordered list of characters
each character is given a unique number
C uses the Unicode character set, a superset of
ASCII
Uses sixteen bits per character, allowing for
65,536 unique characters
It is an international character set, containing
symbols and characters from many languages
Code chart can be found at
http//www.unicode.org/charts/
Character literals are represented in a program
by delimiting with single quotes, e.g.,
'a 'X '7' ' ',
char response Y

31
Common Escape Sequences
32
string

A string represents a sequence of characters,
e.g.,
string message Hello World
string filepath C\\ProCSharp\\First.cs

Strings can be created with verbatim string
literals by starting with _at_, e.g.,
No escape sequence
string a2 _at_\server\fileshare\Hello.cs
string filepath _at_C\ProCSharp\First.cs

33
Types
All types are compatible with object -can be
assigned to variables of type object -all
operations of type object are applicable to them
34
Value Types versus Reference Types
35
Data Input

Console.Read()
Reads a single character from the user
input
Example char c Console.Read()
Console.ReadLine()
Used to get a value from the user input
Example string myString Console.ReadLine()
Convert from string to the correct data type
Int.Parse(), Int16.Parse() Int32.Parse().
Used to convert a string argument to an integer
Allows math to be preformed once the string is
converted
Example string myString 1023 int
myInt Int32.Parse( myString )
Double.Parse(), Single.Parse()

36
Output

Console.Write(exp) prints the exp no end of line
close to 20 overlaods
Console.WriteLine(exp) prints the exp append end
of line
close to 20 overloads
You can use the values of some variables at some
positions of a stringSystem.Console.WriteLine(
0 1., iAmVar0, iAmVar1)
You can control the output format by using the
format specifiersfloat price 2.5f
System.Console.WriteLine(Price 0C.,
price)
output ------------------ Price 2.50.
For a complete list of format specifiers,
seehttp//msdn.microsoft.com/library/en-us/csref/
html/vclrfFormattingNumericResultsTable.asp

Example TaxAndTotal.cs
37
Example

// This program gets 10 grades from the user and
computes their
// average. This is Fig. 4.7 of the textbook.
//
//
using System
class Average1
static void Main(string args)
int total, // sum of grades
gradeCounter, // number of grades
entered
gradeValue, // grade value
average // average of all
grades
// initialization phase
total 0 // clear total
gradeCounter 1 // prepare to loop
// next slide processing phase

38
Example continue

while (gradeCounter lt 10) // loop 10 times
// prompt for input and read grade
from user
Console.Write("Enter integer grade
")
// read input and convert to integer
gradeValue Int32.Parse(Console.ReadL
ine())
// add gradeValue to total
total total gradeValue
// add 1 to gradeCounter
gradeCounter gradeCounter 1
// end of while
// termination phase
average total / 10 // integer
division
// display average of exam grades
Console.WriteLine("\nClass average is
0", average)
// end of method Main
// end of class

39
Arithemtic Operators

Just as in C/Java
Operators can be combined into complex
expressions
result total count / max - offset
Operators have a well-defined precedence which
determines the order in which they are evaluated
Precedence rules
Parenthesis are done first
Division, multiplication and modulus are done
second
Left to right if same precedence (this is called
associativity)
Addition and subtraction are done last
Left to right if same precedence

40
Precedence of Arithmetic Operations
41
Code to test arithmetic operations
// define variables string firstNumber,
secondNumber int number1,
number2 // read two numbers from
the input. Console.Write( "Please enter
the first integer " ) firstNumber
Console.ReadLine() Console.Write(
"\nPlease enter the second integer " )
secondNumber Console.ReadLine() //
convert numbers from type string to type int
number1 Int32.Parse( firstNumber )
number2 Int32.Parse( secondNumber )
// do operations int sum number1
number2 int diff number1 - number2
int mul number1 number2 int div
number1 / number2 int mod number1
number2 Console.WriteLine( "\n0 1
2.", number1, number2, sum )
Console.WriteLine( "\n0 - 1 2.", number1,
number2, diff ) Console.WriteLine(
"\n0 1 2.", number1, number2, mul )
Console.WriteLine( "\n0 / 2 2.",
number1, number2, div )
Console.WriteLine( "\n0 1 2.", number1,
number2, mod )
42
Data Conversions

Sometimes it is convenient to convert data from
one type to another
For example, we may want to treat an integer as a
floating point value during a computation
Conversions must be handled carefully to avoid
losing information
Two types of conversions
Widening conversions are generally safe because
they tend to go from a small data type to a
larger one (such as a short to an int)
Q how about int to long?
Narrowing conversions can lose information
because they tend to go from a large data type to
a smaller one (such as an int to a short)

43
Data Conversions

In C, data conversions can occur in three ways
Assignment conversion
occurs automatically when a value of one type is
assigned to a variable of another
only widening conversions can happen via
assignment
Example aFloatVar anIntVar
Arithmetic promotion
happens automatically when operators in
expressions convert their operands
Example aFloatVar / anIntVar
Casting

44
Data Conversions Casting

Casting is the most powerful, and dangerous,
technique for conversion
Both widening and narrowing conversions can be
accomplished by explicitly casting a value
To cast, the type is put in parentheses in front
of the value being converted
For example, if total and count are integers, but
we want a floating point result when dividing
them, we can cast total
result (float) total / count

Example DataConversion.cs
45
Compatibility Between Simple Types
46
Assignment Revisited

You can consider assignment as another operator,
with a lower precedence than the arithmetic
operators

First the expression on the right hand side of
the operator is evaluated
answer sum / 4 MAX lowest
1
4
3
2
Then the result is stored in the variable on the
left hand side
47
Assignment Operators
48
Increment and Decrement Operators
49
Equality and Relationa Operators
Note the difference between the equality operator
() and the assignment operator ()
Question if (grade 100)
Console.WriteLine( Great! )
50
More Complex (Compound) Boolean Expressions
Logical Operators

Boolean expressions can also use the following
logical and conditional operators
! Logical NOT
Logical AND
Logical OR
Logical exclusive OR (XOR)
Conditional AND
Conditional OR
They all take boolean operands and produce
boolean results

51
Comparison Logical and Conditional Operators

Logical AND () and Logical OR ()
Always evaluate both conditions
Conditional AND () and Conditional OR ()
Would not evaluate the second condition if the
result of the first condition would already
decide the final outcome.
Ex 1 false (x gt 10) --- no need to
evaluate the 2nd condition
Ex 2 if (count ! 0 total /count)

52
Operations on Enumerations
Console.WriteLine(1 4) // bitwise OR
5 Console.WriteLine(1 4) // bitwise AND 0
Console.WriteLine(71) // Error
Console.WriteLine(6 9)// Error
Console.WriteLine(truefalse) // True
Console.WriteLine(true false) // False
Console.WriteLine(!true) // False
53
Precedence and Associativity
high
low
54
Declaration of Local Variables
55
Additional points on local variables

int foo 1
if (foo) Console.WriteLine("yes")
ERROR No implicit conversion between int and
bool
Variables must be assigned before their value is
used
int x,y
if (x gt 5) y x
ERROR x must be assigned before used

56
Conditional Statements

A conditional statement lets us choose which
statement will be executed next
Conditional statements give us the power to make
basic decisions
C's conditional statements
the if statement
the if-else statement
Conitional operator exp1? Va1 val2
the switch statement
All just as in c/Java
(close look at conditional operator and
switch)

57
The Conditional Operator

The conditional operator is similar to an if-else
statement, except that it is an expression that
returns a value
For example
larger (num1 gt num2) ? num1 num2
If num1 is greater that num2, then num1 is
assigned to larger otherwise, num2 is assigned
to larger
The conditional operator is ternary, meaning that
it requires three operands

58
The Conditional Operator

Another example
If count 1, then Quarter" is stored in result
Otherwise, Quarters" is stored

string result int count result (count
lt1 ) ? Quarter Quarters // beginning of
the next statement
59
if Statement Example

char ch // char c Console.Read()
int val
if('0' lt ch ch lt '9')
val ch -'0'
else if('A' lt ch ch lt 'Z')
val 10 ch -'A'
else
val 0
Console.WriteLine("invalid character 0", ch)

60
The switch Statement

The switch statement provides another means to
decide which statement to execute next
The switch statement evaluates an expression,
then attempts to match the result to one of
several possible cases
Each case contains a value and a list of
statements
The flow of control transfers to statement list
associated with the first value that matches

61
The switch Statement Syntax

The general syntax of a switch statement is

switch ( expression ) case value1
statement-list1 case value2
statement-list2 case value3
statement-list3 case ...
62
The switch Statement

The expression of a switch statement must result
in an integral data type, like an integer or
character or a string
Note that the implicit boolean condition in a
switch statement is equality - it tries to match
the expression with a value

63
The switch Statement

A switch statement can have an optional default
case as the last case executed in the statement
The default case has no associated value and
simply uses the reserved word default
If the default case is present, control will
transfer to it if no other case value matches
If there is no default case, and no other value
matches the expression, control falls through to
the statement after the switch
A break statement is used as the last statement
in each case's statement list
A break statement causes control to transfer to
the end of the switch statement

64
switch Statement

Type of switch expressionnumeric, char, enum or
string(null ok as a case label).

Type of switch expression numeric, char, enum
or string (null ok as a case label).
65
switch with goto
66
Loops
67
foreach Statement
68
Jumps
cc int z
int x 7 if(xlt7) goto cc
// error no jump into block Also no
jump out of a class
69
Enumerations

List of named constants
Declaration (directly in a namespace)
How to use

enum Color red, blue, green // values 0, 1, 2
enum Access personal1, group2, all4 1,2,4
enum Access1 byte personal2, group, all //
values 2, 3, 4
The last definition (Access1) is used to save
memory

Color c Color.blue // enumeration constants
must be qualified Console.WriteLine(c) // writes
out blue Console.WriteLine((int)c) //Writes out 1
70
Operations on Enumerations
Color c Color. blue
71
Enumerations, example

enum Season Spring, Summer, Fall, Winter
class Example
public void Method (Season a)
Season b // local variable
private Season c
Season s Season.Fall
Console.WriteLine(s) // writes out 'Fall'
string name s.ToString()
Console.WriteLine(name) // also
writes out 'Fall'
Season y Season.Fall
Console.WriteLine((int) y) // writes out '2'

72
Enumerations, example

using System
public enum Volume byte Low 1, Medium, High
class EnumBaseAndMembers
public static void Main()
Volume myVolume Volume.Low
switch (myVolume)
case Volume.Low
Console.WriteLine("The volume has
been turned Down.")
break
case Volume.Medium
Console.WriteLine("The volume is
in the middle.")
break
case Volume.High
Console.WriteLine("The volume has
been turned up.")
break
Console.ReadLine()

73
Arrays One-dimensional Array

int a new int3
int b new int 3, 4, 5
int c 3, 4, 5
SomeClass d new SomeClass10// Array of
references
SomeStruct e new SomeStruct10// Array of
values
int len a.Length // number of elements in a

74
Multidimensional Arrays

Jagged (like in Java)
nt a new int2
a0 new int3
a1 new int4
int x a01
int len a.Length// 2
len a0.Length// 3
int c new int 2 5 // error

Rectangular (more compact, more efficient access)
int, a new int2, 3
int x a0, 1
int len a.Length // 6
len a.GetLength(0) // 2 return the number
of rows
len a.GetLength(1) // 3 return the number
of columns

75
Arrays Continue

int , b 1, 2 , 3, 4
int , b
b new int 3, 4
string names"Bob", "Ted", "Alice"

76
using System class Array public
static void Main() int myInts 5, 10,
15 bool myBools new bool2 myBools
0 new bool2 myBools1 new
bool1 double, myDoubles new double2,
2 string myStrings new string3 Conso
le.WriteLine ("myInts0 0, myInts1 1,
myInts2 2", myInts0, myInts1,
myInts2) myBools00 true myBools0
1 false myBools10 true Console.WriteL
ine ("myBools00 0, myBools10 1",
myBools00, myBools10)
77

myDoubles0,0 3.17
myDoubles0,1 7.157
myDoubles1,1 2.117
myDoubles1,0 556.00138917
Console.WriteLine ("myDoubles0,0 0,
myDoubles1,0 1", myDoubles0,0,
myDoubles1,0)
myStrings0 "Joe"
myStrings1 "Matt"
myStrings2 "Robert"
Console.WriteLine ("myStrings0 0,
myStrings1 1, myStrings2 2",
myStrings0, myStrings1, myStrings2)

78
strings

string s1 "orange"
string s2 "red"
s1 s2
System.Console.WriteLine(s1) // outputs
"orangered"
s1 s1.Substring(2, 5) // 2 is start
index 5 is length
System.Console.WriteLine(s1) // outputs
"anger
int year 1999
string msg "ahmad was born in "
year.ToString()
System.Console.WriteLine(msg) // outputs
"ahmad was born in 1999"

79
String 2

string s3 "Visual C Express"
System.Console.WriteLine(s3.Substring(7, 2))
// outputs "C"
System.Console.WriteLine(s3.Replace("C",
"Basic")) //outputs "Visual Basic Express
string s4 "Hello, World"
char arr s4.ToCharArray(0, s4.Length) //
be carefull to range, else exception
foreach (char c in arr)
System.Console.Write(c) // outputs
"Hello, World"
string s6 "hi to all"
System.Console.WriteLine(s6.ToUpper()) //
outputs "HI TO ALL"
System.Console.WriteLine(s6.ToLower()) //
outputs "hi to all"

80
Strings 3

string color1 "red"
string color2 "green"
string color3 "red"
if (color1 color3)
System.Console.WriteLine("Equal")
if (color1 ! color2)
System.Console.WriteLine("Not
equal")

81
Strings 4

When comparing strings, the Unicode value is
used, and lower case has a smaller value than
upper case.
string s7 "ABC"
string s8 "abc"
if (s7.CompareTo(s8) gt 0)
System.Console.WriteLine("Greater-than
")//Greater-than
else
System.Console.WriteLine("Less-than")
Will print Greater-than

82
Strings 5

To search for a string inside another string, use
IndexOf(). IndexOf() returns -1 if the search
string is not found otherwise, it returns the
zero-based index of the first location at which
it occurs.
string s9 "Battle of Hastings, 1066"
System.Console.WriteLine(s9.IndexOf("Hastings"))
// outputs 10
System.Console.WriteLine(s9.IndexOf("1967"))
// outputs -1
System.Console.WriteLine(s9.IndexOf('o') //
outputs 7
9 overloads to ndexof may take strat index
length and others

83
String 6

char delimit new char ' '
string s10 "The cat sat on the mat."
foreach (string substr in
s10.Split(delimit) )
System.Console.WriteLine(substr)
//------------------------------------------------
-------
//char delimit new char ' '
char cf ''
string s10 "The cat sat on the mat."
foreach (string substr in s10.Split(cf))
System.Console.WriteLine(substr)

84
Strings 7

string t "Once,UponA/Time\\In\'America"
char sep2 new char ' ', ',', '',
'/', '\\', '\''
foreach (string ss in t.Split(sep2))
Console.WriteLine(ss)

85
Program Example

This program keeps reading int from the keyboard
until -1 is entered. Prints the sum of all entred
numbers. It demonstrate the use of Split and
goto
static void Main(string args)
int x -1
int sum 0
char ar ' '
L1 string inp Console.ReadLine()
foreach (string s in inp.Split(ar))
x int.Parse(s)
sum x
Console.WriteLine(x)
if (x ! -1)
goto L1
Console.WriteLine("the sum is 0",
sum)

86
Example 2 Tax Example

static void Main( string args )
// First get amount
Console.Write( "Please enter amount " )
string amountString
amountString Console.ReadLine() // get
the amount from user
// convert from amount string to floating
point number
float amount Single.Parse( amountString
)
// Next get tax rate
Console.Write( "Please enter tax rate "
)
string taxRateString
taxRateString Console.ReadLine() //
get the tax rate from user
// convert from string to floating point
number
float taxRate Single.Parse(
taxRateString )
// Now compute total
float total amount (1 taxRate)

87
Constructing output strings

int x 12 double y 13.4 float z
12f char c 'a'
string s1 "The sum of " x " and " y "
is " (xy) Console.WriteLine(s1)
s1 "The diff between " x2 " and "
y/2 " is " (x2 - y/2)
Console.WriteLine(s1)
s1 (x y).ToString()
Console.WriteLine(s1)
s1 12.ToString() s1 13
Console.WriteLine(s1)
s1 "" s1 s1 z
cConsole.WriteLine(s1)
s1 "" s1 s1 (z c)
Console.WriteLine(s1)
s1 "" s1 s1 z / c
Console.WriteLine(s1)

88
Numeric Formatting

The full syntax for the format string is
N,MFormatString,
where N is the parameter number, M is the field
width and justification, and FormatString
specifies how numeric data should be displayed.
Item Meaning
C Display the number as currency, using the
local currency symbol and conventions.
D Display the number as a decimal integer.
E Display the number by using exponential
(scientific) notation.
F Display the number as a fixed-point value.
G Display the number as either fixed point or
integer, depending on which format is the most
compact.
N Display the number with embedded commas.
X Display the number by using hexadecimal
notation

89
Format Specifiers Example1

using System
public class FormatSpecApp
public static void Main(string args)
int i 123456
Console.WriteLine("0C", i) // 123,456.00
currency
Console.WriteLine("0D", i) // 123456
decimal
Console.WriteLine("0E", i) // 1.234560E005
exponential
Console.WriteLine("0F", i) // 123456.00
float
Console.WriteLine("0G", i) // 123456 general
Console.WriteLine("0N", i) // 123,456.00
number
Console.WriteLine("0P", i) // 12,345,600.00
percent
Console.WriteLine("0X", i) // 1E240
hexadeciaml

90
Format Specifier Example 2

Console.WriteLine("Currency formatting - 0C
1C4", 88.8,888.8)
Console.WriteLine("Integer formatting - 0D5",
88)
Console.WriteLine("Exponential formatting -
0E", 888.8)
Console.WriteLine("Fixed-point formatting -
0F3",888.8888)
Console.WriteLine("General formatting - 0G",
888.8888)
Console.WriteLine("Number formatting - 0N",
8888888.8)
Console.WriteLine("Hexadecimal formatting -
0X4", 88)

91
Format Specifiers
92
Numeric String Parsing

All the numeric types have a Parse method, which
takes the string representation of a number and
returns you its equivalent numeric value.
string t " -1,234,567.890 "
//double g double.Parse(t) // Same thing
double g double.Parse(t, NumberStyles.Any)
Console.WriteLine("g 0F", g)
The NumberStyles is in System.Globalization

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94
Numeric String Parsing

If you also want to accommodate a currency
symbol, you need the third Parse overload, which
takes a NumberFormatInfo object as a parameter
using System
using System.Globalization
public class FormatSpecApp
public static void Main(string args)
string u " -1,234,567.890 "
NumberFormatInfo ni new NumberFormatInfo()
ni.CurrencySymbol ""
double h double.Parse(u, NumberStyles.Any,
ni)
Console.WriteLine("h 0F", h) // h
-1234567.89

95
Strings and DateTime

A DateTime object stores the date and time

using System public class DatesApp public
static void Main(string args) DateTime
dt DateTime.Now //now is property
Console.WriteLine(dt) Console.WriteLine("
date 0, time 1\n", dt.Date,
dt.TimeOfDay)
96
Boxing and Unboxing

When you change from value type ? reference type
there is a boxing operation, and when you change
from a reference type ? value type there is an
unboxing operation.
Example int f 42 // Value type.
object b f // f is boxed to b.
int x (int)b // Unboxed back to int.
Note
Can Unbox only previously boxed value types.
Can not unbox reference types

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Example