C

1
C - the language for the 2000s

• Judith Bishop
• University of Pretoria, South Africa
• jbishop_at_cs.up.ac.za
• Nigel Horspool
• University of Victoria, Canada
• nigelh_at_uvic.ca

2
Thursday 27 May

• www.cs.up.ac.za
• Choose courses
• Go to bottom of list and choose IRA310
• Sign up for exam, and for tutorials

3
Volunteers on a C course in Africa
Do it in C Naturally!
4
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

5
C Concisely

• First year programming text book due September
  2003
• Addison Wesley, 2003
• Incorporates Views
• Reviewed by Microsoft
• Contents on the Views website
• http//www.cs.up.ac.za /rotor

6
Microsoft Comments

• Many computer books are so heavy that lifting
  them causes a hernia, yet they have less content
  than your favorite tabloid. Many academic text
  books are so boring that they turn your brains to
  dust, yet they don't teach you anything that is
  of use in the real world.
• Not with this book!
• Erik Meijer, Technical Lead, MS Web Data Team

7
Facts on C

• Designed at Microsoft by Anders Hejlsberg
  (Delphi, Java Foundation classes). Scott
  Wiltamuth and Peter Golde
• Language of choice for programming in .NET
• Standardised by ECMA December 2002 and ISO April
  2003  
• It is expected there will be future revisions to
  this standard, primarily to add new functionality.

8
Goals

• general-purpose
• software engineering principles
• software components for distributed environments.
• source code portability
• internationalization
• embedded systems
• Is this Java or C?

9
Why should I know about C?

• A good language, well supported
• Useful for teaching e.g. data structures,
  compilers, operating systems, distributed
  systems, first year
• Inter-language operability via .NET (Java
  doesn't)
• Multi-platform via Rotor (like Java)
• Not tied to an IDE or rapid development (like VB
  or Delphi)
• Efficiency potential (scientific programming)
• Base for future development e.g. XEN

10
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

11
Syntactic niceties

• A slightly enhanced Hello World
• using System
• class Welcome
• static void Main()
• string name " Peter "
• Console.WriteLine("Welcome to C" name)
• Console.WriteLine("It is now "
  DateTime.Now)
• The libraries are the language

12
Some terminology
13
Structured types - structs

• Structs are lightweight - should be used often
• Structs can have fields, methods, properties,
  constructors, operators, events, indexers,
  implemented interfaces, nesting
• Structs cannot have destructors, inheritance,
  abstract

a
struct T int b, c void p ... T a
b c
p function
14
Initialisation

• Struct initialisation rules
• instance fields may not be initialised
• static fields may be initialised
• if there is a constructor, then all fields must
  be initialised there
• if no constructor, values are unspecified

struct T static int a int b, c T
b 4 c 6
a 0 b 4 c 6
15
The System.DateTime struct
// Constructors DateTime (int year, int month,
int day) DateTime (int year, int month, int
day, int hour, int min, int sec) //
Static Properties static DateTime Now
static DateTime Today static DateTime
UTCNow // Instance properties int Day
int Month int Year int Hour int DayOfYear
Plus more
16
Example - Meetings
Console.WriteLine("London New York ") for
(int hour8 hourlt11 hour)
meeting new DateTime (now.Year, now.Month,
now.Day, hour, 0, 0)
offsetMeeting meeting.AddHours(offset)
Console.WriteLine("0t 1t", meeting,
offsetMeeting)
London New York 0800 AM 0300 AM 0900 AM
0400 AM 1000 AM 0500 AM 1100 AM 0600 AM
17
Properties by example

• class TestTutorial
• public static void Main()
• City conference new City
• ("Klagenfurt",
• new DateTime(2003,8,24))
• conference.Meeting new
• DateTime(2003,8,
• tutorial.Meeting.Day-1)
• Console.WriteLine(
• "Speaking at "
• conference.Name
• " on "
• conference.Meeting)

• using System
• struct City
• string name
• DateTime meeting
• public City(string n,
• DateTime m)
• name n
• meeting m
• public DateTime Meeting
• get return meeting
• set meeting value
• public string Name
• get return name

18
A struct vs a class

• struct complex
• double re, im
• complex c
• must define equality and comparison

• class complex
• double re, im
• complex d
• for values, must define equality and comparison

c
d
19
Structured types - classes

• Classes are heavyweight
• Classes can have fields, methods, properties,
  constructors, operators, events, indexers,
  implemented interfaces, nesting
• and destructors, inheritance, abstract

a
class T int b, c void p ... T a
b c VMT
p function
20
Equality

• public override bool Equals(object d)
•     Pet p (Pet) d
•     return namep.name typep.type
• if (igt1 p.Equals(list))
•     Console.WriteLine("Repeated data.")
•    else
• Have to be careful because plist will compile,
  but will compare references

21
Value and reference semantics
22
Type promotion

• The results of a mixed numerical expression are
  promoted to the type with the greater range.
• if either operand is double, the result is
  double,
• otherwise if either operand is long, the result
  is long,
• otherwise the result is int.
• For operations on bytes, the result is always
  converted to an int.
• Division applied to integers produces an integer
  result. So for example we have
• 7 / 3 2
• 3 / 4 0

23
Explicit type conversion

• (typeid) expression or checked ((typeid)
  expression)
• The expression is evaluated and converted to the
  type specified, with possible loss of
  information.
• Real numbers are rounded towards zero to make
  integral values.
• If the type cannot hold the resulting value and
  checking is turned on, an error called an
  OverflowException occurs.
• Placing checked in front of the conversion forces
  the exception to happen, even if the checking
  option is off in the compiler.
• int i 6 double z
• double x 3.14
• double y 5.003000000008E15
• z i // always valid - value is 6.0
• i x // compiler error - must explicitly
  convert
• i y // compiler error - must explicitly
  convert
• i (int) x // valid - value is 3
• i (int) y // execution error if checked is on,
  
• // unspecified value otherwise

24
in, out and ref parameters

• in
• pass by value
• the default
• out
• value copied out only (not in as well)
• used to return multiple values from a method
• ref
• pass by reference
• changes are made to the actual object
• out and ref must be specified by caller and callee

void Rearrange(ref City a, ref City b)
DateTime temp a.MeetingTime a.MeetingTime
b.MeetingTime b.MeetingTime
temp.MeetingTime Rearrange(ref London, ref
NewYork)
25
Visual Studio

• Ive done some overtime today, so the Visual
  Studio .NET 2003 is available for our students
  from today on at the download server I told them
  today. The software is available in the English
  and German (even Chinese) version.  
• For those who dont want to use the Visual
  Studio, the .NET SDK will be available within the
  next few days from the download server.
• http//maniac.stud.uni-karlsruhe.de
• Andreas Heil
• Microsoft Student Consultant
• MAP - Microsoft Academic Program
• Email i-aheil_at_microsoft.com
• Web http//www.studentconsultant.org/unikarlsruhe
  /
• Mobile [phone]

26
Output

• Printing is done using the System.Console class.
  Three approaches
• 1. Use concatenation
• Console.WriteLine(name " " descr " for G"
  price)
• 2. Use ToString
• public override string ToString()
• return name " " descr " for G" price
• Baskets grass, woven for G8.5
• cont ...

27
Formatted output

• 3. Use a format string, where the justification
  and field widths of each item can be controlled
• Console.WriteLine("0 1 for G2,0f2"
• name, descr, price)
• Baskets grass, woven for G8.50

N,Ms
format code e.g. f or C or D
width - default is left, positive means right
item number
28
Formatting other types
NumberFormatInfo f new NumberFormatInfo() f.Cur
rencyDecimalSeparator "," f.CurrencyGroupSepara
tor " " f.CurrencySymbol ""

• Less use of methods through format specifications
• double amount 10000.95
• Console.WriteLine(
• String.Format(f, "0C", amount))
• 10 000,95

29
Control structures

• C has the standard C or Java control
  structures, viz
• for
• if-else and goto!
• while
• do-while
• switch-case
• Conditions must be explicitly converted to bool
• The switch has two very nice features
• case on strings
• Compulsory break after a case

if (s.Length 0) Not if (s.Length)
30
Collections - Arrays

• Arrays are indexed by number e.g.
• int markCounts new markCounts101
• string monthNames new string13
• DateTime myExams new DateTimenoOfExams
• C follows the C/Java tradition of
• Once declared, their size is fixed.
• The indices are integers and start at zero.
• There is a property called Length.
• The elements in the array can be any objects.
• Bounds are always checked (ArrayOutOfBoundsExcepti
  on)

31
Array class

• Corresponding to the type array there is an
  Array class with useful methods e.g.
• Array.BinarySearch(a, v)
• Array.Clear(a, first, num)
• Array.IndexOf(a, v)
• Array.Sort(a)
• Example, including Split

24 8 2003
public Date(string s) string elements
s.Split(' ') day int.Parse(elements0)
month Array.IndexOf(monthNames,elements1)

32
Indexers

• All of these have overloaded, so that they
  can operate exactly like an array in a program
• Cs rich collections include
• Hash tables
• Sorted lists
• Stacks
• Queues
• BitArrays
• ArrayLists

SL
A
0 1 2 3
Wed
A1 SL"Wed"
33
Example of SortedLists

• COS110 350
• GEOL210 80
• ENG100 600
• class Enrollments
• string code
• int size
• public Enrollments(string c, int s)
• code c
• size s
• ... other methods here

34
continued

• Define a list
• SortedList year2003 new SortedList(100)
• Put an object in the list using the same
  notation as for arrays
• year2003"PHY215" new Enrollment("PHY215",
  32)
• Print out the enrollment for Physics
• Console.WriteLine("PHY215 has "
• (Enrollment)year2003"PHY215".size
  "students")
• PHY215 has 32 students

35
Foreach loop

• Designed to loop easily through a collection
• foreach (type id in collection.Keys)
• ... body can refer to id
• Example
• foreach (string course in year2003.Keys)
• Enrollment e (Enrollment) year2003course
• Console.WriteLine(e.code " " e.size)
• Cant say foreach (string course in year2003)
  Why?

36
Demonstration 1 - Public Holidays

• The Public Holidays Program
• Illustrates
• switch on string
• sorted lists
• indexers
• Split
• file handling
• GUI specification described later

37
Output from the demo
38
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

39
Views Vendor independent extensible windowing
system

• SSCLI (and Rotor) has no GUI capability
• General move to platform independent GUIs
• Views is a Rotor Project to provide GUI
  specifications and a rendering engine using XML
  and a toolkit such as Qt or Tcl/TK
• Available on http//views.cs.up.ac.za

40
GUI building today
41
(No Transcript)
42
Example in WinForms
show.Click new
EventHandler(ActionPerformed) hide.Click new
EventHandler(ActionPerformed) p
ublic void ActionPerformed(Object src,
EventArgs args) if (src
show) pic.Show() else if (src hide)
pic.Hide()

• Embedded in 115 lines of generated code labelled
  do not touch
• Unexplained classes and unused objects here

43
A GUI using XML
44
Example in Views
XML
Views.Form f new Views.Form(_at_"ltFormgt
ltverticalgt lthorizontalgt ltButton
NameShow/gt ltButton NameHide/gt
lt/horizontalgt ltPictureBox Namepic
Image'CJacarandas.jpg' Height175/gt
lt/verticalgt lt/Formgt" )
string c for () c f.GetControl()
PictureBox p (PictureBox) f"pic" if (c
null) break switch (c) case Show"
p.Show() break case Hide"
p.Hide() break
C

• No pixel positioning
• No generated code
• Separation of concerns

45
Demo 2 - ShowHide

• Winforms
• Make some changes
• Views
• Make some changes

46
The Views Notation
form ltformgt controlGroup lt/formgt controlGroup lt
verticalgt controlList lt/verticalgt
lthorizontalgt controlList lt/horizontalgt controlList
control textItemList ltitemgt text lt/itemgt
control controlGroup ltButton/gt
ltCheckBox/gt ltCheckedListBoxgt textItemList
lt/CheckedListBoxgt ltDomainUpDowngt textItemList
lt/DomainUpDowngt ltGroupBoxgt radioButtonList
lt/GroupBoxgt ltLabel/gt ltListBox/gt
ltOpenFileDialog/gt ltSaveFileDialog/gt
ltPictureBox/gt ltTextBox/gt ltProgressBar/gt
ltTrackBar/gt radioButtonList ltRadioButton/gt
47
A typical control - Button
ON

• ltButton/gt NameS
• TextS
• ImageF
• WidthM
• HeightM
• ForeColorC
• BackColorC
• Creates a push button which is a variable given
  by the Name S.
• The button can be labelled with a Text string or
  with an Image or both.
• The size of the button defaults to something
  large enough to hold the label, either text or an
  image or can be set with Width and Height.
• Clicking the button causes GetControl to return
  with the name of the control.

ltButton NameonButton TextON /gt
Compulsory
48
The Handler methods
Essentially five kinds of methods construct clo
se getControl get put PLUS direct access
Form(string spec,params) The constructor. void
CloseGUI( ) Terminates the execution thread
string GetControl( ) Waits for the user to
perform an action string GetText(string
name) Returns the value of the Text
attribute int GetValue(string name) Returns the
Value attribute from TrackBar, ProgressBar and
CheckBox int GetValue(string name, int index)
Returns the status of CheckBox at position
index void PutText(string name, string
s) Displays the string in a TextBox or ListBox
control. void PutValue(string name, int
v) Sets an integer value associated with a
ProgressBar or CheckBox
49
Views.Form v new Form (_at_"ltform Text Luckygt
ltverticalgt ltTextBox name Number Text
'13'/gt ltButton name Start/gt
ltListBox name Day Width 270/gt
lt/verticalgt lt/formgt") int luckyNumber
int.Parse(v.GetText("Number")) Random r
new Random (luckyNumber) for( )
string s v.GetControl( ) if (snull)
break switch (s) case "Start"
DateTime luckyDate new
DateTime(DateTime.Now.Year, r.Next(3,12),
r.Next(1,30)) v.PutText("Day", "Your
lucky day will be "
luckyDate.DayOfWeek " " luckyDate.ToString("M"
)) break
50
Multiple controls - arrays in XML?

• Arrays of product names and images
• Arrays of prices (in the background)

double unitCost new doublemaxNumProducts
string item new stringmaxNumProducts ltB
utton Name??? ImageApples.gif
Width72 Height72/gt
51
XML Positional parameters
// Set up Form parameter itemcount
product formParameters2count product
formParameters2count1 product ".gif"
// Construct the form form new
Views.Form(v_specs, formParameters) // Part of
the Form specification ltverticalgt ltButton
Name0 Image1 Width72 Height72/gt
ltButton Name2 Image3 Width72 Height72/gt
ltButton Name4 Image5 Width72
Height72/gt lt/verticalgt // Handle a specific
product select Array.IndexOf(item,c)
52
Demo 3 - Till Program

• Till Program
• Till Program amended
• Removing an product (see Run method)
• Adding controls (see ReadData method)
• Writing to a ListBox (see ReadDataFile method)
• Reacting to the Button (see ReadDataFile method)
• Emergence of scrollbars

53
Acquiring more control

• Views.Form f new Views.Form( _at_"ltformgt
  ltverticalgt
• ltLabel Namelabel1 Text'Enter Your Name '/gt
• ltTextBox Namebox1 Width150/gt
• lt/verticalgt
• lt/formgt"
• creates in the Views engine a hash table of
  controls with the keys being the strings of the
  Name attributes
• Access to an individual control may be obtained
  by using the indexer operation, and that access
  may be used to achieve run-time effects.
• TextBox tb fbox1"
• tb.Font new Font(FontFamily.GenericMonospace,
  10)
• Label lab flabel1"
• lab.BackColor Color.Red
• f.Invalidate()  // force form to be redrawn with
  new colours

54
Cross platform

• XWT-XUL Control Engine in Java and ActiveX
  Rendering via XUL.CSS in Mozilla
• SWT (not XML based) Rendering efforts for Win,
  GTK, Mac Supported by IBM and Eclipse
• Views Engine and rendering in Tcl/TK, using
  Rotor for Unix, Win and MacOSX (Rajwinder)

55
Cross Language

• XML-XUL Independent schema and specs
  Handlers in JavaScript, in the XML
• SWT For Java only, uses JNI to get to OS
• Views Schema is WinForms oriented but can be
  used in Java with JNI wrapper to the engine
  (Worrall and Lo)

56
XUL example (for Tic-Tac-Toe)
lt!-- main.xwt --gt ltxwtgt lttemplate
thisbox"frame" width"220" height"260"
color"black"gt ltbox
orient"vertical"gt ltboxgt
ltcell id"northwest"gtlt/cellgt
ltcell id"north"gtlt/cellgt
ltcell id"northeast"gtlt/cellgt
lt/boxgt .. and two more of these
lt/boxgt lt/templategt lt/xwtgt lt!--
cell.xwt --gt ltxwtgt lttemplate hpad"5"
vpad"5"gt ltbox color"white"
width"44" height"44" id"inner"gt
lt/boxgt lt/templategt lt/xwtgt
Procedures
57
XUL handlers
lt!-- cell.xwt --gt ltxwtgt lttemplate
hpad"5" vpad"5"gt _Press1
function() if (state
"empty") state "x"
_state
function(s) if (s "empty")
inner.image null
else if (s "x")
inner.image "x" else if
(s "o") inner.image
"o"
ltbox color"white" width"44" height"44"
id"inner"gt lt/boxgt
lt/templategt lt/xwtgt
JavaScript
58
UIML from Harmonia
lt?xml version"1.0"gt lt!DOCTYPE uiml ...
"uiml2_0g.dtd"gt ltuimlgt ltinterfacegt
ltstructuregt ...lt/structuregt
ltstylegt ...lt/stylegt ltcontentgt
...lt/contentgt ltbehaviorgt
...lt/behaviorgt lt/interfacegt
ltpeersgt ltlogicgt ...lt/logicgt
ltpresentationgt...lt/presentationgt
lt/peersgt lt/uimlgt
ltstructuregt ltpart id"TopLevel"
class"JFrame"gt ltpart id"L"
class"JLabel"/gt ltpart id"Button"
class"JButton"/gt lt/partgt lt/structuregt
59
UIML Handlers
ltbehaviorgt ltconditiongt ltevent
class"actionPerformed" part-name"Button"/gt
lt/conditiongt ltactiongt
ltproperty part-name"L" name"text"gt
ltcall name"Counter.increment"/gt
lt/propertygt lt/actiongt lt/behaviorgt

• Very Java-based
• Intended to map from UIML to Java, C, HTML, WML,
  VoiceXML)
• Our experiments in 2000 on mapping to applets,
  WML and HTML showed this to be A bridge too
  far (Bishop, Ellis, Roux and Steyn)

60
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

61
Extensibility

• Inheritance
• For classes and interfaces, not structs
• No multiple inheritance
• Used for closely coupled extensibility
• Interfaces
• Can have methods, properties, indexers and events
• Used for loosely coupled extensibility
• Abstract classes
• Used to force redefinition of methods
• All can have class modifiers
• For accessibility and versioning

62
Modifiers etc

• this keyword refers to the current instance of a
  type
• Accessibility options
• public access everywhere default for enums and
  interface members
• protected access within a class and its
  derivatives
• internal access within a type default for
  non-nested types
• private access within a type default for
  structs and classes
• other
• readonly declarations that can be assigned
  only once
• sealed prevents inheritance

63
Interfaces vs inheritance
INTERFACES
INHERITANCE
64
Inheritance - virtual functions

• overridden
• base class specifies virtual, and derived class
  may supply another version using override
• overridden abstract
• base class specifies virtual abstract, and
  derived class must supply another version using
  override

virtual V
OR
virtual V
override V
virtual abstract V
65
Virtual functions cont.

• hidden
• base class supplies a virtual function of the
  same name as an existing derived class function.
  Override is not assumed. Derived class should be
  recompiled with function specified as new, to
  make the separation explicit.

F
1 2 3
virtual F
F
virtual F
new F
66
Demonstration 4 - StarLords

• Illustrates
• inheritance
• base constructor calling
• virtual and override
• ref parameters

67
Program output
68
Boxing and unboxing

• Value types are implicitly promoted to the object
  type or an interface type implemented by the
  value type
• an object instance is created and and the value
  copied in
• object o
• int i 6
• o i
• The object type can be explicitly converted to a
  value-type or from any interface type that
  implements the value type
• the object is checked to be a value of the value
  type, then the value is copied out of the
  instance.
• i (int) o

69
Using the IComparable Interface

• IComparable interface
• public int CompareTo(object obj)
• The meaning of the comparison is defined in the
  method itself.
• Returns negative, zero, or positive
• IComparable is used by the sorting and searching
  methods already defined for the Array and other
  collections.
• It is already implemented for the basic types
  such as int and string, and also for all the
  types defined in the System namespace, such as
  DateTime.
• The comparison is not a bitwise one, but can be
  intelligently defined to suit the type.

70
Example - a small Staff class

• struct Staff
• string name
• int startDate
• public Staff(string n)
• name n
• startDate
• DateTime.Now.Year
• public string Name
• get return name
• public int StartDate
• get return startDate
• public override string
• ToString ()
• return "Staff "name

• Sort an array of Staff using Array.Sort
• The elements must implement IComparable
• public int CompareTo(object o)
• return (name.CompareTo
• (((Staff) o).name))
• Sort calls CompareTo, treating the elements of
  the array as objects. We unbox to treat them as
  Staff
• Array.Sort(staffList,0,n)

Unboxing
71
Alternative comparator methods

• IComparer interface
• public int Compare(object x, object y)
• We can force the Sort method to use a specific
  Compare method
• Array.Sort(staffList,0,n,compareByDate)
• A new compare method can check dates
• public class StaffByDate IComparer
• public int Compare(object x, object y)
• return (((Staff)x).startDate.
• CompareTo(((Staff) y).startDate))
• This class is declared inside the Staff class.
  Then we can instantiate an object and pass it to
  the extended version of Sort as follows
• Array.Sort(staffList,0,count,new
  Staff.StaffByDate())

72
Class Conversions

• A class may be implicitly upcast to a class that
  it derives from or that it implements.
• It may be explicitly downcast to a class that
  derives from it. This explicit downcast may fail.
  
• objectname is typename - returns true or false
• objectname as typename - converts or returns
  null
• (typename) objectname - converts or raises
  exception
• public int CompareTo(object o)
•   if (o is Staff)
•     return (name.CompareTo(((Staff) o).name))
•   return -1

73
Operator overloading

• DateTime struct
• public static DateTime operator
•                 (DateTime d, TimeSpan t)
• e.g. birth 18
• Not allowed for new ( )
• implicit can be used to make casting automatic
• public static implicit operator
• CheckBox(GenObject RHS)
• return (CheckBox)RHS.Control
• enables an object of type Control to be treated
  as a CheckBox without a conversion
• Indexer is not overloaded, but defined like a
  property with get and set.

74
Serialisation

• Persistence of objects on the net or on disks or
  a server
• All classes marked as Serializable can have
  their objects send out with writeObject and
  retrieved with readObject.
• C offers
• CLR-centric serialization using soap and XML or
  all graphs
• CLR-centric binary serialisation
• And clean XSD schemas and XML for most graphs
• The XML serialising is done via SOAP
• SoapFormatter swrite new SoapFormatter ()
• Swrite.Serialize(output,st)
• SoapFormatter sread new SoapFormatter ()
• Fromdisk (theType) sread.Deserialize(input)
• Where output and input are the same stream

75
Demonstration 5 Access control

• Card access control system
• Illustrates
• Interfaces
• Polymorphism
• Operator overloading
• Serialisation

76
Delegates

• Delegates allow references to methods
• They separate methods from a specific name
• One step up from interfaces

C
Delegates
Interfaces
Inheritance
77
Simple graphics

• Drawing is done in an OnPaint method
• protected override void OnPaint (PaintEventArgs
  e)
• or in a Handler connected to a Paint event
• public void whatever (Object source,
  PaintEventArgs e)
• this.Paint PaintEventHandler (whatever)
• Images can be displayed using drawimage
• E.Graphics.DrawImage(Image.FromFile(photo.jpg),0
  ,0)
• Drawing can be integrated with Views

78
Demonstration 6 Selecting images

• Illustrates
• Drawing
• Events
• Images
• Views

79
Other C goodies

• Enumerations - System.Enum can write and read
  them!
• Param modifier allows variable number of
  parameters
• Assemblies for archiving compiled classes,
  metadata, images etc
• Reflection can make programming very powerful
• Extensive namespaces
• Proposals for
• Generics
• Anonymous methods
• Iterators
• Namespace alias qualifier
• Partial type declarations

80
Generics

• Part of the Rotor Gyro download
• Defined in the OOPLSA paper by Kennedy and Syme
• Better approach than dynamic polymorphism (based
  on object supertype) - safety, expressivity,
  clarity, efficiency
• Stack s new Stack()
• s.Push((int)s.Pop()(int)s.Pop())
• Stack ltintgt s new Stack ltintgt ()
• s.Push(s.Pop()s.Pop())
• Extension to the CLR giving exact runtime types,
  dynamic linking, and shared code

81
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

82
Threads

• Threads are objects of the System.Threading class
• They are initiated by linking to a ThreadStart
  delegate and supplying a callback method.
• using System.Threading
• Thread t new Thread (
• new ThreadStart(object.RunMethodName)).Start
• public void RunMethodName()
• some loop
• statements
• possibly containing calls to
  Thread.Sleep(n)

83
Demonstraion 7 Ticking Clock

• Ticking Clock
• Illustrates
• Threads
• Delegates and events
• Integrating it with Views

84
Web requests
Support for Several protocols In a uniform way
85
Socket communication
Standard socket Communication With
uniform streams
86
Remoting

• Three kinds of remote objects
• Single call
• Singleton
• client-activated
• Leases created for objects transported outside
  the application
• Objects are hosted by
• A managed executable
• IIS (Internet Information Server)
• .NET component services
• Use serialization for transporting data
• Metadata and configuration files enable
  cross-language programming

87
Remoting scenarios
88
Example - a Server
using System using System.Runtime.Remoting using
System.Runtime.Remoting.Channels using
System.Runtime.Remoting.Channels.Tcp namespace
Project public class RunServer public
static int Main(string args)
TcpChannel chan new TcpChannel(int.Parse(port))
ChannelServices.RegisterChannel(chan)
RemotingConfiguration.RegisterWellKnownServiceTy
pe (Type.GetType("Project.Server,
Server"), "Server", WellKnownObjectMode
.Singleton) Server server (Project.Server) //
customised Activator.GetObject(typeof(
Project.Server), "tcp//" "localhost"
"" "8085" "/Server")
server.Prepare()
89
Demo 8 Currency Calculator

• Illustrates extensive client server with remoting

90
Contents

• Introduction
• Basic C
• GUIs with Views
• Advanced OOPS
• Networking
• Technical considerations

91
.NET offerings
Rotor - Microsofts Implementation of the CLI
(plus some)
Microsoft Windows Web service Framework
SSCLI
.NET
CE
92
(No Transcript)
93
RotorSSCLI- a Shared Source CLI

• Microsofts implementation of the CLI, Code name
  Rotor
• Free, modifiable and redistributable CLI
  implementation
• Platform independent Currently executes on MS
  Windows, FreeBSD and Mac OS/X
• Practically identical to .NET, but with retooled
  JIT compiler and GC, and extensions such as
  generics
• Programmed in C an C
• Other implementations of CLI are Ximians Mono
  and DotGNUs Portable.NET

94
A compliant CLI Implementation
VS.NET
System.Web (ASP.NET)
System.WinForms
System.Drawing
C
System.Data (ADO.NET)
System.Xml
SDK Tools
System
Common Language Runtime

Windows Platform
95
Rotor CLI Implementation
VS.NET
System.Web (ASP.NET)
System.WinForms
System.Drawing
System.Data (ADO.NET)
System.Xml
SDK Tools
System
Common Language Runtime


Platform Abstraction
96
Runtime Architecture

• Three main tasks
• Loading and executing
• Memory management
• Security management
• The SSCLI makes the interactions easier to follow
• Class structure
• ClassLoader (in csload.h) manages the loading of
  IL and metadata and when the JIT compiler will
  run
• FJit (in fjit.h) reads IL and produces machine
  code
• GCHeap (gc.h) handles memory management and
  garbage collection

97
Core classes in the runtime
98
Hello World in IL

• Hello.Main in IL
• .method public hidebysig static void Main() cil
  managed
• .entrypoint
• Idstr "Hello, World!"
• call voidmscorlibSystem.ConsoleWriteLine(st
  ring)
• ret
• .NET provides a managed code environment for
  handling IL and metadata, using the JIT compiler.
• It is easy to understand the process on Rotor

99
Hello.Main in x86 Native Code

• //Function Prologue
• push ebp
• mov ebp,esp
• push esi
• xor esi,esi
• push esi
• push ecx
• push edx
• //set stack frame to zero
• mov ecx,1
• addr_a
• push 0
• loop addr_a
• //load "Hello, World" and call Console.WriteLine
• mov eax, ltconstant string table entygt
• mov eax,dword ptr eax
• mov ecx,eax
• push ecx
• mov eax, Console.WriteLine

100
The Size of Rotor

• Entire SSCLI package is big
• 16 MB download
• FastChecked binary build approx. 70MB, 1200
  classes, 20 DLLs, 20 EXEs
• 27MB of C and C, 8MB of C, some assembly code
• Source binary approx. 600MB, 6000 files
• Missing APIs
• Much needed WinForms GUI toolkit(see Views)
• Database connectivity
• Debugging
• Rotor not guaranteed to be bug-free
• Debugging tool similar to GDB/JDB

101
Why use Rotor?

• Shared source
• Source code and binaries are free
• Useful for testing and experimentation
• Useful for CS education
• Provides for open platform development
• Platform independent
• PAL facilitates CLI deployment on many platforms
• Cross-platform
• Remoting provides convenient language independent
  middleware
• Standard
• ECMA and ISO
• Strong international academic community support

102
Where to get C

• ECMA specs
• http//msdn.microsoft.com/net/ecma
• Microsoft commercial C and CLR SDK
• http//msdn.microsoft.com/downloads
• Shared source info (Rotor) for non-Windows
  platforms
• http//www.microsoft.com/sharedsource
• Microsoft Academic Alliance
• http//www.msdnaa.net/

103
Further Reading

• Bishop Judith and Horspool Nigel, C Concisely,
  Addison Wesley, due out September 2003
• Peter Drayton, Ben Albahari, Ted Neward, C in a
  Nutshell, OReilly, 2002
• Troelsen, Andrew C and the .NET platform A!
  press 2001
• Damien Watkins, Mark Hammond and Brad Abrams,
  Programming in the .NET environment, Microsoft
  .NET Development Series, Addison Wesley, 2002
• Visual Studio help files
• DevHood tutorials -- see http//www.devhood.com
• http//www.cs.up.ac.za/rotor -- for the Views
  project