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

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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)

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Strings 7

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

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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)

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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)

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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)

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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

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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

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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)

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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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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)
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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

97
Example

• using System
• namespace box
• enum colorred,green
• struct student
• public int id // must be public in order
  to accessable
• public char gender
• class Program
• static void Main(string args)
• color c color.green
• int f 42 // Value type.
• student s
• s.id 11
• s.gender 'f'

98
Example Continue

• object b f // f is boxed to b.
• object cc c
• object dd s
• Console.WriteLine(cc.ToString())
  //green
• cc b
• Console.WriteLine(cc.ToString())//42
• int x (int)b // Unboxed back to
  int.
• color co (color)cc
• Console.WriteLine(co.ToString())
  //42
• student ss (student)dd //Unboxed
  back to student
• Console.WriteLine(ss.id) //11
• Console.WriteLine(ss.gender) //'f'

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Boxing and Unboxing
100
Boxing and Unboxing
This Queue can then be used for reference types
and value types