High Level Languages

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High Level Languages
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Here we go.

• Course is split up into 3 sections
• Delphi (Windows Programming)
• Perl (Server Programming)
• PHP (Web Programming)
• Delphi PHP taught by James Goulding.
• Perl taught by Chris Coleman.
• Web www.cs.nott.ac.uk/jog/HLL

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Here we go.

• Lectures
• Wednesday 13.00 (C3)
• Friday 09.00 (LT2)
• Labs
• Monday 16.00 18.00 (A32)
• Coursework
• 1 coursework for each section
• Total of 3 courseworks, each with identical
  weight
• NO EXAM!

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High Level Languages

• Section 1
• Delphi

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Book List

• A booklist can be found on the course Web page.
• The recommended text for Delphi is
• SAMS Teach Yourself Borland
• Delphi 5 in 21 Days
• By Reisdorph (available at amazon.co.uk - 24hr
  delivery - accessible through the HLL Web Page).

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What are HLL?

• Low Level Languages
• - Machine Code, Assembler
• Mid Level Languages
• - Java, C, Pascal, C
• High Level Languages
• - Visual Basic, CBuilder, Delphi

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Graphical User Interfaces

• GUIs require complicated code and are incredibly
  labour intensive
• Almost impossible to program GUIs using
  procedural programming
• Easier using OO techniques, but by no means
  simple, and very intimidating.
• RAD systems were created to deal with this
  problem.

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• PASCAL!

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What HLL are on offer?

• Visual Basic
• Visual C
• Visual J
• CBuilder
• JBuilder
• Delphi

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What Is Visual Basic?

• Widely Used Microsoft RAD suite
• Evolved from MS Basic
• Visual Front End
• Heavily modified Basic as underlying language
• Pros Very Popular
• Some Object Orientation
• Extensive Database Capability
• Cons One Major drawback

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What Is Visual Basic?

• BASIC is absolute rubbish

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What are Visual C/J?

• Microsofts RADs for C and Java
• Use slightly modified versions of C and an
  incredibly incompatible version of Java.
• Most widely used languages for creating
  professional
• Windows applications
• Used to write apps such as Word and Excel.
• Microsofts environments are VERY clumsy

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What Is Delphi?

• Delphi is a RAD product, written by Borland.
• You can create Win32 console GUI programs for
  Windows very quickly and easily.
• You can use drag-and-drop techniques to create
  the user interface to a program.
• Many debugging tools
• Fully Object Orientated
• Extensive Database capability
• True Windows Compiler hence very efficient
• The language underlying Delphi is an OO version
  of

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• PASCAL!

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The Delphi IDE

• You will find a copy of Delphi 5 on the computers
  in the IT Terminal Room (A32).
• This program provides you with the Delphi
  integrated development environment (IDE), used to
  produce your Delphi applications.
• The Delphi IDE is divided into 3 parts
• Toolbars Component Palette
• Object Inspector
• Delphi Workspace

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The Delphi IDE
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Toolbars Component Palette

• The toolbars allow you to access tasks such as
  opening, saving and compiling objects.
• The component palette contains a wide array of
  components that you can drop onto your forms,
  e.g. buttons, text labels, etc.
• A component is a self-contained binary piece of
  software that performs some specific predefined
  function.
• They are divided into groups. To place a
  component on a form just choose it and click
  where you want it to appear on your form.

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The Object Inspector

• The object inspector is on the left side of the
  Delphi IDE.
• Use the object inspector to modify a components
  properties and events.
• A component property controls how the component
  operates, e.g. color property.
• The events tab contains a list of events for a
  component. Events occur as the user interacts
  with a component. You write the event handling
  code.

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The Delphi Workspace

• The workspace initially displays the Form
  Designer. The Form Designer enables you to create
  forms.
• A form might be the programs main window, a
  dialog box or any other type of window.
• Behind the Form Designer is the Code Editor. This
  is where you type the code when writing your
  programs.

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Object Pascal Language

• Before you can learn the RAD features of Delphi,
  you need to learn the basics of the Object Pascal
  language.
• Object Pascal forms the backbone of Delphi, and
  is obviously based heavily on Pascal, which was
  taught in Semester 1 to MA students in the ICP
  module.
• I will provide an overview of the Object Pascal
  language. Extra reading may be necessary for a
  complete understanding of the language.

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• PASCAL!

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History of Pascal

• In 1994, Borland began working on a RAD tool
  called Delphi.
• Borland needed to decide on a programming
  language that would be the heart of the system.
• Since they were the only vendor of a Pascal
  compiler, they had much control over changes to
  the language.
• They developed a new language, called Object
  Pascal, essentially their latest update to Turbo
  Pascal, and packaged it in Delphi.

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Is Pascal Dead?

• Clearly Not Pascal is still widely used in
  various new guises.
• It is a vital part of Delphi, which is still a
  prolific RAD.
• Only recently Component Pascal has been
  integrated into the new Microsoft .net
  environment, alongside C. Interestingly there is
  no place for Java.

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Why has it survived?

• It has a large user base
• It is a very robust language (not case sensitive)
• It is very easy to debug.
• It is efficient.
• It is very powerful, featuring
• - full object orientation
• - dynamic memory allocation
• - pointers

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Object-Oriented Programming

• An object reveals to the user only as much as is
  needed, hence using an object simplifies
  programming.
• Internal mechanisms of an object are hidden from
  the user. This is especially notable for objects
  that control a graphical interface.
• Objects and classes will be discussed later this
  section.

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Pascal Units

• A unit, in Pascal, is a text file that can be
  compiled into a module of code. It contains
  Pascal language code, written by the programmer.
• A Delphi application consists of at least two
  units.
• A Project Source Unit contains project source
  code. It is not usually edited manually (not
  recommended either). Has file extension .DPR.

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Pascal Units

• A Form Unit contains the source code for a
  particular form in your application. It has
  extension .PAS.
• There is always at least one form unit, in a
  Delphi application, representing the main form.
• There are also units that contain only source
  code this is library code.

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Anatomy of a Unit

• The project source for a default Delphi unit
• program Pop_Rivals
• uses
• Forms,
• Unit1 in GirlsAloud.pas Form1
• R .RES
• begin
• Application.Initialize
• Application.CreateForm(TForm1, Form1)
• Application.Run
• end.

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Project Source

• The program keyword identifies the unit as a
  programs main source unit.
• The uses keyword specifies the various other
  units that are needed to compile the program.
• The R .RES is called a compiler directive
  which tells Delphi to include project resources.
• The main code is between begin and end.
• The main code initialises, creates and runs the
  application (Details not necessary).

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A Blank Pascal Unit

• unit Unit1
• Interface
• Implementation
• end.
• The start of a unit always has the unit keyword
  followed by the units name.
• It always ends with an end keyword terminated by
  a full-stop (.)

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The Interface Section

• The interface keyword marks the start of the
  Interface Section of a unit.
• The interface section is the section in which
  identifiers exported from this unit are declared.
• An exported identifier is one that can be
  accessed by other units in the project.
• The end of the interface section is marked by the
  implementation keyword (see next slide).

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The Implementation Section

• The implementation section of a unit is the
  section that contains the actual code for the
  unit.
• In essence, the interface is where you declare a
  function and the implementation is where you
  define that function.

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Example

• A unit with a public function
• unit Unit1
• interface
• procedure javaIsRubbish
• implementation
• procedure javaIsRubbish
• begin
• Code for javaIsRubbish goes here
• end
• end.

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The const keyword

• The const section of a unit is where you would
  declare all the constants to be used in that
  unit.
• ...
• interface
• const
• AppCaption My Program
• procedure DoSomething
• implementation
• ...
• A const in the interface section is available to
  other units.

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The var keyword

• The var keyword is used to declare a section of
  code in which variables are declared.
• A var section can be declared at different levels
  of scope at the unit level, in a procedure or in
  a function, e.g.
• var
• X Integer
• MyArray TMyArray

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Comments in Code

• Comments are placed between curly braces.
• This may be a little confusing for any Java or
  C programmers in the room! e.g.
• this is a comment on one line
• this is a comment
• and it is on more than
• one line

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Object Pascal Techniques

• Variables
• Operators
• Arrays
• Strings
• Decisions
• Loops

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1. Variables

• Variables are declared in the var section
  (discussed earlier).
• Variables can be declared within functions
• var
• S string declaration
• I integer
• begin
• S Hello World! assignment
• Label1.Caption S
• end

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Variable Types

• There are various variable types available

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2. Object Pascal Operators

• Operators are similar to in other languages
• Addition x y z
• Subtraction x y z
• Multiplication x y z
• Real number division x y / 3.14
• Integer division x y div 10
• Logical AND if (x1) and (y2) then
• Logical OR if (x1) or (y2) then

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Object Pascal Operators

• More operators
• Equal to if (x10) then
• Not equal to if (xltgt10) then
• Less than if (xlt10) then
• Greater than if (xgt10) then
• Less than / equal to if (xlt10) then
• Greater than / equal to if (xgt10) then

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Converting Between Data Types

• Object Pascal performs conversion between data
  types when possible.
• However, when converting an integer to a string,
  the following function is useful
• var
• X SmallInt
• begin
• X 3200
• Label1.Caption IntToStr(X)
• end

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3. Arrays

• An array is declared as follows
• var
• MyArray array0..4 of Integer
• This array contains the individual elements
  myArray0, myArray1, myArray2, myArray3,
  myArray4.

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4. Strings

• Strings are dynamically allocated memory in
  Delphi. To declare a string use
• var
• S string dynamically allocated string
• To get the length of a string use the Length
  function.

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Concatenating Strings

• Strings can be concatenated
• var
• S1 string
• S2 string
• begin
• S1 James
• S2 Goulding
• Label1.Caption S1 S2
• end

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More on Strings

• To access individual elements of a string, treat
  the string as a character array. However, the
  array starts at index 1, not 0.
• You can also compare strings using the usual set
  of operators , ltgt, lt, gt, lt, gt.
• There are many string manipulation functions
  available. You can look them up in a Pascal or
  Delphi reference book, or try the on-line help in
  the Delphi RAD environment.

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5. Decisions

• The structure of an if statement in Pascal is as
  follows

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Switch Statements

• Switch statements look like this example
• case expression of
• value_1 statements_1
• value_2 statements_2
• ...
• value_n statements_n
• else
• begin
• end
• end

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6. Loops

• The syntax of the For loop in Pascal is
• for initial_value to end_value do begin
• statements
• end
• For example
• for I 0 to 9 do begin
• Memo1.Lines.Add(Iteration IntToStr(I))
• end

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The While Loop

• An example while loop looks like this
• var
• X Integer
• begin
• X 0
• while X lt 1000 do begin
• X DoSomeBoringCalculation
• DoMoreBoringStuff
• end
• ... more code
• end

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The Repeat Loop Statement

• The repeat loop repeatedly executes a block of
  code indicated by statements as long as the
  conditional expression cond_expr is False.
• repeat
• statements
• until cond_expr

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Continue Break

• The continue procedure is used to force program
  execution to the bottom of the loop, skipping any
  statements that come after it.
• The break procedure is used to halt execution of
  a loop prior to the loops normal test condition
  being met.
• The exit procedure causes the whole program to
  terminate if it is called within the main program
  block.

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Useful Functions

• Inc(A) will increase the value of A by 1. This is
  similar to A in Java.
• Dec(A) will decrement the value of A by 1.
• Pred(A) will return the value of the predecessor
  to A. So if A is 10 it will return 9.
• Succ(A) will return the value of the successor to
  A.

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On-line Tutorials

• Delphi is too big to teach in 6 lectures
• You will be required to do some form of
  self-learning and practicing outside of lectures.
• I will link some Borland on-line tutorials to the
  course Web site for you to look at. There will
  also a link to the ICP module Web site and an
  Object Pascal Language Guide.