Delphi Interview Questions

.dcp

Define custom message
const
  WM_MY_MESSAGE = WM_USER + 0;

Define handler for message
  type
  TMyForm = class(TForm)
  private
    procedure OnMyMessage(var Msg: TMessage); message WM_MY_MESSAGE;

Send or Post message
  PostMessage(self.Handle,WM_MY_MESSAGE,0,0)

Through event handlers. You can also define your own messages using the WMUSER constant.

TGraphicControl vs TWinControlThe TGraphicControl class provides the capability to have controls which are not windowed controls (they have no window handle). TWinControl is the base class from whic...

To add a new code unit in Delphi
choose File-New ... Unit.

//**blank code unit

unit Unit2;
interface
{interface code goes here}
implementation
{implementation code goes here}
end. //this ends the unit

Declaration
ADynamicCharArray :  ^CharArrayType;

Allocation
ADynamicCharArray := AllocMem(NumChars * sizeof(char));

Release
FreeMem(ADynamicCharArray, NumChars * sizeof(char));

By using the finalize keyword

Components are commonly of two kinds

Visual and Non-visual

Ex. Visual
Labels
Edit boxes
A visual component is one that helps make graphical building blocks.

Ex. Non-visual
TQuery
TThread/Timer

This wizard helps you to build a Database Form with Ttabale, TDatasource and all the TDatabaseEdit Control without you droping each component.

Cheers,
Vijay

The initialization section is optional. It begins with the reserved word initialization and continues until the beginning of the finalization section or, if there is no finalization section, until th...

Every delphi unit(pas file) you can have Initialization and Finalization section which will be executed during unit load and unlond respectively

Unit2.pas

unit Unit2;

interface

uses
implementation

Initialization
//Do your Initialization Steps Here
Finalization
//Do your Finalization Steps Here
end.

Set the form's autoscroll property to true.

There are two types of arrays. 1.Static - array[indexType1, ..., indexTypen] of baseType
2. Dynamic - array of baseType

File with .dpr extension is the project file. It comprises all the unit names used in the application along with their path in the hard disk (and the form name if the unit is associated with a .dfm fi...

Interface clause is used to represent the interface scetion in delphi. The interface contains the type declarations, var declarations.

Tform is the .dfm file associated with any delphi application. Tform acts as a parent and owner for the components placed on it. Every .dfm file has a .pas file associated with end.

Object Pascal

unit {unit name}
uses
interface
type
end;
var
implementation

Container is used to hold the components. It's the responsibility of the container to request the visible controls placed on it to paint themselves. The container is also responsible for creating and...

TActiveForm is the base class for a VCL Form exposed as an ActiveX control. TActiveForm represents a form that is created by a class factory (in Delphi) or using the Active Template Library (C++) and ...

  It is a function in Delphi to find the Total memory status.It accepts TMemoryStatus variable as var parameter.It fills the variable entity with different memory status info like Total phisical...