Function and Procedure

There are two kind of subroutine in Pascal : Function and Procedure. The difference between these subroutines is in return value. Function gives a return value, but procedure doesn’t. The structure of function and procedure are the same :

Here is the example of procedure and function :

program FunctionAndProcedure;
{$APPTYPE CONSOLE}
uses
   SysUtils;

procedure Add1(x, y : integer);
 var
  z : integer;
begin
  z := x + y;
  writeln(x,' + ',y,' = ',z,' (using procedure)');
  readln;
end;

function Add2(x, y : integer) : integer;
begin
  Add2 := x + y;
end;

begin
  Add1(25,10);
  writeln('25 + 40 = ',Add2(25,40),' (using function)');
  readln;
end.

You can download the complete code here.

The Complete Electronic Circuit

(Dancing Lamp #3)

In my previous tutorial, I’ve given you the example program and the LED circuit. But what you’ve got is only a small electronic circuit on your table. How about if you want to use bigger light bulbs instead of using LED. Here is the complete electronic circuit : 

You have to connect parallel port ground pin out to the circuit ground. Just be careful while connecting this circuit to your computer, or it will damage your computer !!! Make sure that everything is in the place.

Using this circuit, if you send a “high” to the data pin out (D0 .. D7), it will trigger the transistor. It will be saturated, and let current flows through the relay and the light bulb will be connected to the electricity and light on. Use this circuit for each data pin out of your parallel port.

Previous tutorials about dancing lamp :

Accessing your PC’s parallel port using Inpout32.dll in Delphi

LED Circuit

LED Circuit

(Dancing Lamp # 2)

To test the program I’ve created in my previous tutorial, I use this circuit (see picture). But be careful while you connect this circuit to your parallel port. Make sure that every component is in the right place or connection, otherwise it will damage your PC !!!

I use 1 KOhm resistors. If you send an integer data = 15 to the parallel port, D0…D3 LED will be light on. And D4…D7 LED will be off.

You can arrange which LED is on or off by writing some codes in Delphi. And you can also set the delay of each step you turn on or off the LED using OnTimer event of Timer component in Delphi. I’ve created an example program for you.

Download the example program here.

Go to previous tutorial (Accessing your PC’s parallel port using Inpout32.dll in Delphi)

Go to next tutorial (The Complete Electronic Circuit)

Accessing your PC’s parallel port using Inpout32.dll in Delphi

(Dancing Lamp # 1)

Before we create a dancing lamp using our PC’s parallel port, we have to know the parallel port female pin-out (see the picture below).

D0 is the LSB (Least Significant Bit) and D7 is the Most Significant Bit (MSB). You can send an integer type data to the D0..D7 pin-outs. And the output will be the binary form of the integer we send. For example : If we send an integer data 15 the output will be :

D7	D6	D5	D4	D3	D2	D1	D0
LOW	LOW	LOW	LOW	HIGH	HIGH	HIGH	HIGH

15 (byte) = 00001111 (binary)

How To Send Data To The Parallel Port ?

To send data to the parallel port I use a DLL file (Inpout32.dll) that can be downloaded at logix4u.net, and it’s free for non-commercial manner. Place this file in C:\WINDOWS\system or in the same folder with you project you’re going to create.

To use this file you can see my previous tutorial about using a DLL file. This DLL file contains a function called Out32(). The syntax of this function :

                                                    Out32(portaddress,data);

Usually, the port address is $378 (you can check the BIOS setting of your PC) 

Example program :

unit Unit1;

interface

uses
   Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
   StdCtrls;

type
   TForm1 = class(TForm)
   Edit1: TEdit;
   Label1: TLabel;
   Button1: TButton;
   procedure FormActivate(Sender: TObject);
   procedure Button1Click(Sender: TObject);
private
  { Private declarations }
public
  { Public declarations }
end;

var
   Form1: TForm1;

implementation

{$R *.DFM}
function Out32(wAddr:word;bOut:byte):byte; stdcall; external 'inpout32.dll';

procedure TForm1.FormActivate(Sender: TObject);
begin
  Edit1.Text := '';
  Edit1.SetFocus; 
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Out32($378,StrToInt(Edit1.Text));
end;

end.

You can download the complete code here.

Go to next tutorial (LED Circuit)

Pointer

Pointer is a variable that points toward a memory address. So a pointer is a data address. The data is somewhere else. Below picture will show you the relationship between a pointer and a data pointed by a pointer.

To declare a pointer, use the below statement :

Type

   PointerType : ^Type;

In this case, type can be an integer, a real, an array or record. And you can see the example code of using a pointer :

program Project1;
   {$APPTYPE CONSOLE}
uses
   SysUtils;

type
   PointerType = ^integer;

var
   MyPointer : PointerType;
   Data : integer;

begin
  Data := 100;
  MyPointer := @Data;
  writeln('Data pointed toward by the pointer is ', MyPointer^);
  Data := 123;
  writeln('Data pointed toward by the pointer is ', MyPointer^);
  readln;
end.

Disposing pointer allocation

To free the memory that is used by a pointer, you can use dispose statement.

  Dispose(pointer);

Example :

program Project1;
   {$APPTYPE CONSOLE}
uses
   SysUtils;

var
   MyPointer : ^integer;

begin
  New(MyPointer); // allocate memory
  MyPointer^ := 100;
  writeln('Vallue pointed toward by MyPointer is ',MyPointer^);
  Dispose(MyPointer); // free memory allocation
  readln;
end.

You can download the complete code here.

Record’s variant

A record can have one or more variant elements or fields. This variant allows data to accessed using one or more different fields. To declare a record contain variant use these statements :

Type

   RecordTypeName = record

      Field_1 : type_1;

      ..

      ..

      Field_n : type_n;

      Case Tag : OrdinalType of

         Constant_1 : ( variant_1);

         Constant_2 : ( variant_2);

      End;

Example record contain variant :

Type

   TCategory = (FullTimer, PartTimer);

   TEmployeeRecord : record

     Name : String(30);

     Case Category : TCategory of

       Full Time : ( Salary : currency;

                              Bonus : currency);

       Part Time : (  Salary : currency);

     End;

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TCategory = ( FullTimer, PartTimer );
   TEmployeeRecord = record
       Name : String[30];
       Case Category : TCategory of
          FullTimer : ( Salary : currency;
                                  Bonus : currency);
          PartTimer : ( Payment : currency);
   end;

var
   Employee : TEmployeeRecord;

begin
  with Employee do
    begin
     // assigning fields' values
     Name := 'Albert Einstein';
     Category := FullTimer;
     Salary := 1000;
     Bonus := 100;
     // writing fields' values
     writeln('Name : ',Name);
     writeln('Salary : ',Salary:10:2);
     writeln('Bonus : ',Bonus:10:2);
     // assigning fields' values
     Name := 'Albert Einstein';
     Category := PartTimer;
     Payment := 500;
     // writing fields' values
     writeln('Name : ',Name);
     writeln('Payment : ',Payment:10:2);
    end;
  readln;
end.

You can download the complete code here.

Accessing Record’s Elements

After we declare a record ( previous tutorial ), now we are going to access the elements or fields of the record. The fields in a record can be accessed using this notation :

    RecordName.RecordField

Between the field name and the record name separated by a dot.

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TRecordItem = record
     Item : string;
     Quantity : integer;
     Price : currency;
   end;
var
   ItemStock : TRecordItem;

begin
  // assigning values to record's fields
  ItemStock.Item := 'USB Flash Disk';
  ItemStock.Quantity := 20;
  ItemStock.Price := 10;
  // writing teh fields' values.
  writeln('Item : ',ItemStock.Item);
  writeln('Quantity : ',ItemStock.Quantity,' pc/s');
  writeln('Price : $ ',ItemStock.Price:10:2 );
  readln;
end.

Using with statement

With statement allows us to access a record field without mentioning the record name. The syntax of with statement is :

 with Record do
   begin
     statements
   end;

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TRecordItem = record
     Item : string;
     Quantity : integer;
     Price : currency;
   end;
var
ItemStock : TRecordItem;

begin
  with ItemStock do
    begin
      // assigning values to record's fields
      Item := 'USB Flash Disk';
      Quantity := 20;
      Price := 10;
      // writing teh fields' values.
      writeln('Item : ',Item);
      writeln('Quantity : ',Quantity,' pc/s');
      writeln('Price : $ ',Price:10:2 );
    end;
  readln;
end.

You can download the complete code here.

Record

Record is a structured data type. It contains some elements or fields, and each field can have a different data type. See the picture below.

How to declare a record ?

You have to declare a record after type clause.

type

    RecordTypeName = record

       Field_1 : DataType;

       .

       .

       Field_n : DataType;

    End;

var

   RecordName : RecordTypeName;

For example, we declare a record named ItemStock that has three fields ( Item, Quantity and Price ).

type

   TRecordItem = record

     Item : string;

     Quantity : integer;

     Price : currency;

   end;

var

   ItemStock : TRecordItem;

First, define a TRecordItem then use it to declare a variable named ItemStock. So the ItemStock variable has three fields : Item, Quantity and Price.

Memory Game

In this project, we are going to create a memory game. I think there are three steps of creating a memory game.

Step 1 : Create the form / user interface

Step 2 : Set the properties of the components

Step 3 : Write the code

Step 1 : Create the form / user interface

First you have to create a form with some image components, a label, a start button, a  timer and an exit button. You can set any width or height properties of your components you use. And arrange them like the picture below or you can use your own arrangement.

Then cover all images with buttons. So your form will be like this :

Step 2 : Set the properties of the components

Now, set the properties of all components we use in this project like tables below :

Form

Property	Value
Caption	MEMORY GAME
Position	poDesktopCenter

Buttons

Component	Property	Value
StartButton	Name	StartButton
	Caption	&Start
ExitButton	Name	ExitButton
	Caption	&Exit
Button1 .. Button20	Caption	?

Label

Property	Value
Caption	MEMORY GAME

Images

Property	Value
Stretch	true

Timer

Property	Value
Interval	1000
Enabled	false

Step 3 : Write the code

Before we start writing the code, we need to prepare some pictures for this project. I have prepared 30 pictures that you can download (jpg format). Or you can have your own pictures. If your pictures are in jpg format, you have to declare it in the uses clause.

uses

  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls,       jpeg;

To see the complete code, you can download this project here.

Example program of using BinaryToInteger.DLL

In this example, we are going to create a program that can convert an eight binary data into an integer value using BinaryToInteger.DLL. Before we start, you have to create a user interface like this picture.

Every edit box holds a bit of binary data. So there is a byte binary data (8 bits) that will be converted into an integer value. A binary data holds ‘0’ or ‘1’, so we need to limit the input of each edit box. And the code will be :

procedure TForm1.bit8KeyPress(Sender: TObject; var Key: Char);
begin
  if not (key in ['0','1',#8,#13]) then 
    key:=#0
      else
        bit7.SetFocus;
end;

To use BinaryToInteger.DLL, you must declare the function after {$R *.DFM}

{$R *.DFM}
function BinToInt(S : String): integer; stdcall; external 'BinaryToInteger.dll';

Don forget, you must place your BinaryToInteger.DLL in the same folder with this project, or you can place this DLL file in the directory : c:\windows\system.

The code of OnClick even of ConvertButton :

procedure TForm1.ConvertButtonClick(Sender: TObject);
var
  BinaryData : string;
begin
  BinaryData := bit8.Text + bit7.Text + bit6.Text + bit5.Text +
  b it4.Text + bit3.Text + bit2.Text + bit1.Text;
  IntegerValue.Caption := IntToStr(BinToInt(BinaryData));  
end;

You can download the complete code of this example program here.

BinaryToInteger.DLL

Now, we're going to create a DLL file named BinaryToInteger.DLL This DLL is for converting “a character string of binary” into an integer value.

Example :

‘11111110’ = 254

The complete code of BinaryToInteger.DLL (click to download)

library BinaryToInteger;

uses
   SysUtils,
   Classes;

{$R *.RES}

function BinToInt(S : string) : integer; stdcall;
var
  DataLength, i, j, buffer, buffer1 : integer;
begin
  DataLength := Length(S);
  buffer1 := 0;
  for i := 1 to DataLength do
    begin
      buffer := StrToInt(S[i]);
      for j := 1 to DataLength-i do buffer := buffer*2;
      buffer1 := buffer1 + buffer;
    end;
  BinToInt := buffer1;
end;

exports
  BinToInt;

begin
end.

To use this DLL file, you can see the example of using BinaryToInteger.DLL

Dynamic Array

Dynamic array is an array that has no fix amount. To declare a dynamic array you can use this syntax :

Array of datatype;

Example :

    Var

       MyArray : array of integer;

This array is dynamic with integer data type. The memory of array is not allocated. To allocate memory of array use SetLength procedure.

Example :

    SetLength(MyArray, 5);

    SetLength(MyArray, 2, 3);

    SetLength(MyArray, 2, 3, 5);

It will allocate an array which has five elements. In this case the index will be 0, 1, 2, 3, 4. And to free the array memory, set nil value to the array. 

Example :

    MyArray := nil;

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
   i, sum : integer;
   MyArray : array of integer;
begin
  SetLength(MyArray, 5);
  MyArray[0] := 12;
  MyArray[1] := 14;
  MyArray[2] := 16;
  MyArray[3] := 18;
  MyArray[4] := 20;
  sum := 0;
  for i:= 0 to Length(MyArray) -1 do
   begin
     sum := sum + MyArray[i];
   end;
  writeln(sum);
  readln; 
end.

You can download the complete code here.

3-Dimensional Array

3-dimensional array is an array that has three indexes. To understand the concept of 3-dimensional array, see the picture below.

To declare 3-dimensional array that can hold 24 character, we can us this statement :

Type

    TwoDimensionalArray = array[1..2, 1..3, 1..4] of char;

Var

    TheData : TwoDimensionalArray;

Or you can use this statement :

Var

    TheData : array[1..2, 1..3, 1..4] of char;

To access an element in 3-dimensional array use this syntax :

ArrayVariableName[ArrayIndex1, ArrayIndex2, ArrayIndex3];

Example :

TheData[1,3,4] := ‘A’;

Writeln(TheData[1,3,4]);

Readln(TheData[1,3,4]);

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
   i, j, k : integer;
   Thedata : array[1..2, 1..3, 1..2] of char;
begin
  TheData[1,1,1] := 'A';
  TheData[1,1,2] := 'B';
  TheData[1,2,1] := 'C';
  TheData[1,2,2] := 'D';
  TheData[1,3,1] := 'E';
  TheData[1,3,2] := 'F';
  TheData[2,1,1] := 'G';
  TheData[2,1,2] := 'H';
  TheData[2,2,1] := 'I';
  TheData[2,2,2] := 'J';
  TheData[2,3,1] := 'K';
  TheData[2,3,2] := 'L';
  for i := 1 to 2 do
   begin
     for j := 1 to 3 do
       begin
         for k := 1 to 2 do writeln(TheData[i,j,k]);
       end;
   end;
  readln; 
end.

You can download the complete code here.

N-Dimensional Array

N-dimensional array is an array that has two or more indexes. To understand the concept of n-dimensional array, see the picture below.

To declare two-dimensional array that can hold six character, we can us this statement :

Type

    TwoDimensionalArray = array[1..2, 1..3] of char;

Var

    TheData : TwoDimensionalArray;

Or you can use this statement :

Var

    TheData : array[1..2, 1..3] of char;

To access an element in two-dimensional array use this syntax :

ArrayVariableName[ArrayIndex1,ArrayIndex2];

Example :

TheData[1,3] := ‘A’;

Writeln(TheData[1,3]);

Readln(TheData[1,3]);

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;
var
   i, j : integer;
   TheData : array[1..2, 1..3] of char;
begin
   //assigning values to array
   TheData[1,1] := 'A';
   TheData[1,2] := 'B';
   TheData[1,3] := 'C';
   TheData[2,1] := 'D';
   TheData[2,2] := 'E';
   TheData[2,3] := 'F';
   for i := 1 to 2 do
    begin
      for j := 1 to 3 do writeln(TheData[i,j]);
    end;
   readln;
end.

You can download the complete code here.

How to declare a three-dimensional array and to use it in a program ?

Array Data Type

Array is a structured data type that can hold some data which has same data type. Every element in an array has an index and it can be individually accessed. In Pascal, we can have one-dimensional array or n-dimensional array.

To declare one-dimensional array that can hold six character, we can us this statement :

Type

    OneDimensionalArray = array[1..6] of char;

Var

    TheData : OneDimensionalArray;

Or you can use this statement :

 

Var

    TheData : array[1..6] of char;

The statement above declares an array that can hold six elements. It is called static array, because it has a fix amount of data. While a dynamic array does not have a fix amount of data.

To access an element in an array use this syntax :

ArrayVariableName[ArrayIndex];

Example :

TheData[3] := ‘A’;

Writeln(TheData[3]);

Readln(TheData[3]);

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;
var
   i : integer;
   TheData : array[1..5] of char;
begin
   //assigning values to array
   TheData[1] := 'A';
   TheData[2] := 'B';
   TheData[3] := 'C';
   TheData[4] := 'D';
   TheData[5] := 'E';
   for i := 1 to 5 do writeln(TheData[i]);
   readln;
end.

You can download the complete code here.

Creating Web Photo Gallery using Photoshop

It is quite simple to create a web photo gallery. Before we start creating a web photo gallery, first you have to group all picture you are going to use in your photo gallery into a folder / directory. Then you also need to prepare a folder / directory as a destination of your photo gallery.

After you run Adobe Photoshop, choose File – Automate – Web Photo Gallery. See the picture below :

A dialog box will appear. Choose the style of your photo gallery ( in this case I use simple style ) and the extension of your index file ( htm or html ). Define the directories or folders of your source images / pictures and the destination folder. In this case, I group all images / pictures in folder : D:\Fujiyama and the destination folder is D:\MyWebPhotoGallery. See the picture below :

Press OK and relax while Adobe Photoshop is processing your images / pictures. After processing, you will get some folders and files as the result in the destination folder.

Now, you ready to upload all the files to your web server.

Download pictures and web photo gallery here

Break and Continue Statement ( Delphi Tutorial # 14 )

Break

Break is a procedure to jump out or quit the looping statement (if, repeat or while). Break is usually called in an if statement.

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  number, stop : integer;
begin
  write('Conter will be stopped at : ');
  readln(stop);
  for number := 1 to 1000 do
    begin
      if number = stop +1 then break;
      writeln(number);
    end;
  readln;
end.

Continue

Continue is a procedure that is used for skipping to next iteration in a looping statement (if, repeat or while). It is also called in an if statement.

Example 1 (writing odd numbers from 1 to 20) :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  number : integer;
begin
  for number := 1 to 20 do
    begin
      if Odd(number) then continue;
      writeln(number);
    end;
  readln;
end.

Example 2 (writing even numbers from 1 to 20) :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  number : integer;
begin
  for number := 1 to 20 do
    begin
      if not Odd(number) then continue;
      writeln(number);
    end;
  readln;
end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

While Statement in Delphi ( Delphi Tutorial # 13 )

The syntax of while statement is :

  while boolean expression do

    begin

      first statement

      .

      .

      last statement

    end;

If the boolean expression is true, the statements will be executed until the boolean expression is false.

Example 1 ( writing numbers from 1 to 10 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

  SysUtils;

var

 number : integer;

begin

 number := 1;

 while number  <  11 do

  begin

   writeln(number);

   number := number + 1;

  end;

 readln;

end.

Example 2 ( adding numbers from 1 to 100 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

  SysUtils;

var

 number, sum : integer;

begin

 number := 1;

 sum := 0;

 while number   <  101  

  begin

   sum := sum + number;

   number := number + 1;

  end;

 writeln(sum);

 readln;

end.

Example 3 ( adding odd numbers from 1 to 10 ) :program Project1;

program Project1;

{$APPTYPE CONSOLE}

uses

  SysUtils;

var

 number, sum : integer;

begin

 number := 1;

 sum := 0;

 while number   <  101

  begin

   if Odd(number) then sum := sum + number;

   number := number + 1;

  end;

 writeln(sum);

 readln;

end.

Example 4 ( adding even numbers from 1 to 100 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

  SysUtils;

var

 number, sum : integer;

begin

 number := 1;

 sum := 0;

 while number   <  101

  begin

   if not Odd(number) then sum := sum + number;

   number := number + 1;

  end;

 writeln(sum);

 readln;

end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

Repeat Statement in Delphi ( Delphi Tutorial # 12 )

The syntax of repeat statement is :

  repeat

    first statement

    .

    .

    last statement

  until boolean expression

The first statement until the last statement will be executed once. If the boolean expression is false, all statements will be executed again until the boolean expression is true.

Example 1 ( writing numbers from 1 to 10 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
  number : integer;
begin
  number := 1;
  repeat
   writeln(number);
   number := number + 1;
  until number = 11;
  readln;
end.

Example 2 ( adding numbers from 1 to 100 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
  number, sum : integer;
begin
  number := 1;
  sum := 0;
  repeat
   sum := sum + number;
   number := number + 1;
  until number = 101;
  writeln(sum);
  readln;
end.

Example 3 ( adding odd numbers from 1 to 10 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
  number, sum : integer;
begin
  number := 1;
  sum := 0;
  repeat
   if Odd(number) then sum := sum + number;
   number := number + 1;
  until number = 101;
  writeln(sum);
  readln;
end.

Example 4 ( adding even numbers from 1 to 100 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

var
  number, sum : integer;
begin
  number := 1;
  sum := 0;
  repeat
   if not Odd(number) then sum := sum + number;
   number := number + 1;
  until number = 101;
  writeln(sum);
  readln;
end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

Looping Statement in Delphi ( Delphi Tutorial # 11 )

Looping statement is used for repeating a process. For example, if we want to write numbers from 1 to 100, we can use looping statement instead of writing a hundreds statements. In Pascal, there are three looping statements :

-         for  statement

-         repeat  statement

-         while statement

We have break statement and continue statement related to repetition process.

For statement

The syntax of for statement :

-         for counter :=  first value to last value do

-         for counter :=  first value downto last value do

Counter is an ordinal type variable (see Delphi Tutorial # 3 : Identifier and Data Type). First value and last value are expressions which data type is the same as counter’s data type. Counter’s value will change from the first value to the last value. And in every step of counter, the statement will be executed.

Example 1 :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  number : integer;
  letter : char;
begin
  for number:=1 to 5 do
   writeln(number);
  for letter:='A' to 'E' do
   writeln(letter);
  for number:=5 downto 1 do
   writeln(number);
  for letter:='E' downto 'A' do
   writeln(letter);
  readln;
end.

Example 2 (adding numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils; 

var
  i, sum : integer;
begin
  sum := 0;
  for i:=1 to 100 do
   begin
    sum := sum + i;
   end;
 writeln(sum);
 readln;
end.

Example 3 (adding odd numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  i, sum : integer;
begin
  sum := 0;
  for i:=1 to 100 do
   begin
    if Odd(i) then
     sum := sum + i;
   end;
  writeln(sum);
  readln;
end.

Example 4 (adding even numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
  SysUtils;

var
  i, sum : integer;
begin
  sum := 0;
  for i:=1 to 100 do
   begin
     if not Odd(i) then
       sum := sum + i;
   end;
  writeln(sum);
  readln;
end.

You can download the complete code here

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Multiple Conditional Statements in Delphi ( Delphi Tutorial # 10 )

You can use if statement for multiple conditional statement but it will be little bit messy.

For example :

program multiple_cond_if;
{$APPTYPE CONSOLE}
uses
 SysUtils;

var
 mark : integer;
begin
 write('Your mark : ');
 readln(mark);
 write('Your grade is ');
 if mark >= 90 then
  writeln('A')
 else
  if mark >= 70 then
   writeln('B')
  else
   if mark >= 60 then
    writeln('C')
   else
    if mark >= 40 then
     writeln('D')
    else
     writeln('E');
 readln;
end.

Instead of using if … then statement, it will be easier using case … of statement :

program multiple_cond_case;
{$APPTYPE CONSOLE}
uses
 SysUtils;

var
 mark : integer;
begin
 write('Your mark : ');
 readln(mark);
 write('Your grade is ');
 case mark of
  0..39   : writeln('E');
  40..59  : writeln('D');
  60..69  : writeln('C');
  70..89  : writeln('B');
  90..100 : writeln('A');
 end;
readln;
end.

Download the complete code here.

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Using DLL file in Delphi

After we created a DLL file in the previous tutorial, now we’re going to use this DLL file in an application. First, you have to create a user interface like picture below :

Or you can download this project here.

Before you write some codes in this project, you have to make sure that the DLL file you’re going to use and your project are in the same directory (folder). Or you can put the DLL file you’re going to use in directory : c:\windows\system.

To use functions in a DLL file we’ve created, you must type the function after {$R *.DFM}

{$R *.DFM}
{ place functions from DLL here }
function area(length, width : integer): integer; stdcall; external 'area_volume.dll';
function volume(length, width, height : integer): integer; stdcall; external 'area_volume.dll';

external clause means that the functions we use (area and volume) are in an external file (area_volume.dll)

To call area function and volume function see the codes below :

procedure TForm1.CalculateAreaButtonClick(Sender: TObject);
var
  L, W : integer;
begin
  L := StrToInt(Edit1.Text);
  W := StrToInt(Edit2.Text);
  Label8.Caption := Label8.Caption + ' ' + IntToStr(area(L,W));
end;

procedure TForm1.CalculateVolumeButtonClick(Sender: TObject);
var
  L, W, H : integer;
begin
  L := StrToInt(Edit3.Text);
  W := StrToInt(Edit4.Text);
  H := StrToInt(Edit5.Text);
  Label9.Caption := Label9.Caption + ' ' + IntToStr(volume(L,W,H));
end;

area(L,W) and volume(L,W,H) will return integer type values, so if you want to put these values into label.caption, you have to convert them into string using IntToStr() procedure.

You can download the complete code here.

if Statement in Delphi ( Delphi Tutorial # 9 )

There are two kinds of conditional statement : if statement and case statement. This both statements are for making decisions that involve two or more alternative choices or conditions.

In this tutorial, we will learn about if statement. There are two kinds of if statement :

-         if ….. then

-         if ….. then …. else

The syntax of if …. then statement is :

     If boolean expression then statement;

Boolean expression can be true or false. If it is true, computer will execute the statement. If it is false, computer will not execute the statement.

The syntax of if …. then …. else statement is :

     If boolean expression then first_statement else second_statement;

If boolean expression is true, computer will execute the first statement. If it is false, computer will execute the second statement.

The flowchart of if statement is below :

Example for if …. then statement :

program Project1;

{$APPTYPE CONSOLE}

uses SysUtils;

var

 score : integer;

begin

  write('Your score : ');

  readln(score);

  if score < 60 then writeln('You did not pass the exam');

  if score >= 60 then writeln('You passed the exam');

  readln;

end.

Example for if …. then …. else statement :

program Project2;

{$APPTYPE CONSOLE}

uses

  SysUtils;

var

 score : integer;

begin

  write('Your score : ');

  readln(score);

  if score < 60 then

    writeln('You did not pass the exam')

   else

    writeln('You passed the exam');

  readln;

end.

 

Both projects above will give you the same result.

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Creating DLL file using Delphi

There are two kinds of  executable file in Windows, EXE file and DLL file. DLL (Dynamic Link Library) is an executable file with some procedures or functions in it. These procedures or functions can be used by some applications at the same time. Because, once DLL is loaded to memory, every program or application can use it. The other advantage of using DLL is our application becomes modular. It will be easier to change the application by replacing the DLL.

To create a DLL file, choose File – New – DLL. And you’ll get some codes below :

library Project1;

{ Important note about DLL memory management: ShareMem must be the first unit in your library's USES clause AND your project's (select Project-View Source) USES clause if your DLL exports any procedures or functions that pass strings as parameters or function results. This applies to all strings passed to and from your DLL--even those that are nested in records and classes. ShareMem is the interface unit to the BORLNDMM.DLL shared memory manager, which must be deployed along with your DLL. To avoid using BORLNDMM.DLL, pass string information using PChar or ShortString parameters. }

uses

  SysUtils,

  Classes;

{$R *.RES}

begin

end.

You can delete the unnecessary comment after library clause and add exports clause before begin….end block.

One thing you have to concern about is that all variables in DLL are private. Your application and DLL can not use the variables at the same time. You have to send values of the variables and receive a result.

Now we’re going to insert some functions into DLL :

library area_volume;

uses

  SysUtils,

  Classes;

{$R *.RES}

function area(length, width : integer): integer; stdcall;

begin

 area := length*width;

end;

function volume(length, width, height : integer): integer; stdcall;

begin

 volume := length*width*height;

end;

exports

 area, volume;

begin

end.

You can download this source code here.

Now save the project as area_volume.dpr. Remember that the project name and the DLL name have to be the same, in this case we name it area_volume. Then build the DLL file by choosing Project – Build … And you’ll get area_volume.dll file. Then you can create an application using this DLL.

Square Root and Exponential Function in Delphi ( Delphi Tutorial # 8 )

Sqrt() function

In this tutorial we’re going to write some mathematic formulas in Delphi. The first formula is :

To write the above formula in Delphi, we use sqrt() function :

Sqrt((b*b-4*a*c)/(2*a))

Exp() function

There’s no power operator in Pascal Object. But it does not mean that we can not calculate the formula above. Before we calculate the formula, we have to describe it into an exponential function :

So we can write the formula using exp() function and ln() function :

                                                   Exp(b*ln(a))

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
x, y : real;
a, b, c : integer;

begin
  // Insert user code here
  a := 2;
  b := 5;
  c := 3;
  x := sqrt((b*b-4*a*c)/(2*a));
  writeln(x:0:1);
  y := exp(b*ln(a));
  writeln(y:0:0);
  readln;
end.

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