Delphi KB: Language Basics Topic

This primer is intended for those just getting started in Delphi and focuses on displaying things.

Create a classic "Hello, World" Windows native code Console App using Delphi. This tutorial is based on Borland Developer Suite 2006 but you can use any version of Delphi you wish. In this tutorial, you will create a classic "Hello, World!" windows console application. A console application is a type of Windows application that has FULL access to the Win32 API, but it's GUI is limited to a DOS-like text window. When Windows starts a console application, it creates a text-mode console window where the program can display text and the user can interact with the program via the keyboard.

Delphi uses := for it's assignment operator.

Object Pascal is generally not case sensitive.

Object Pascal requires the semi-colon after the "declaration" part.

Delphi uses // for a single line comment and both {} and (**) for multiple line comments. Although you can nest different types of multiple line comments, it is recommended that you don't. A special comment. Delphi compiler directives are in the form of {$DIRECTIVE}. Of interest for comments is using the $IFDEF compiler directive to remark out code.

In Delphi, you define constants similar to how you define variables but use the Const keyword instead of the Var keyword. Declare global constants in a unit's interface section and unit constants (scope limited to unit) in the implementation section. Declare local constants above the begin..end block.

Languages Focus: Development Tools

Primary development tool(s) used to develop and debug code.

Languages Focus: End of Statement

In coding languages, common End of statement specifiers include a semicolon and return (others exist too). Also of concern when studying a language is can you put two statements on a single code line and can you break a single statement into two or more code lines.

Common source code file extensions include:

• .BDSPROJ - Project, Borland Developer Studio project file holds compiler options, etc. This is the file you open.
• .DCU - Delphi Compiled Unit file.
• .DFM - Delphi Win32 form file (a text resource file).
• .DPR - Delphi project file. Primary project "source" file.
• .PAS - Delphi unit source file.

Notice in the more complete example that the semicolon for the begin..end block after end is not included. That tells the compiler something else is coming (the statement is not finished). Also note the semicolon is missing right before the final "else" statement.

Note: The following example uses floating point literals. In Delphi, to specify a fractional floating point literal between 1 and -1, you preceed the decimal with a 0; otherwise, you will get a compiler error (i.e. .1 + .1 does not work).

Literals are single quoted (the apostrophe) as in 'Prestwood'. If you need to embed an apostrophe use two apostrophies in a row.

Delphi logical operators:

Language Overview: Delphi programming language is a type-safe language consisting of hybrid traditional Pascal and OOP features. You code either in a traditional approach using functions, procedures, and global data, or you code using an OOP approach, or a mixture of both.

Target Platforms: Delphi for Win32 is most suitable for creating native code Win32 applications that run on Microsoft Windows.

Object Pascal allows parameters of the same type to be listed together, separated by commas, and followed with a single data type (more params of different data types can follow, after a semi-colon). The default for parameters is by value. For by reference, add var in front of the parameter. Object Pascal also offers constant parameters where you add const in front of the parameter. A constant parameter is like a local constant or read-only parameter the compiler can optimize. You cannot assign a value to a constant parameter, nor can you pass one as a var parameter to another routine.

Use the + operator to concatenate two strings. Use IntToStr to convert an integer to a string and FloatToStr to convert a floating point number to a string.

An operation with only one operand (a single input). In Object Pascal, a unary operator always precedes its operand (for example, -B), except for ^, which follows its operand (for example, P^). The Delphi unary operators are +, -, and ^ (pointer).

The TYPE operator is also a unary operator and is�evaluated at compile time. The TYPE operator returns the size in bytes of the operand,

Declare global variables in the interface section of a unit, variables declared within the implementation section (but not within a method) have a scope limited to the unit. You declare local variables in a var block outside (above) your begin..end code block. You cannot declare variables in-line (inside begin..end). You can initialize global and unit variables but you cannot initialize local variables. Delphi offers many variable types. Some common variable types include String, WideString, PChar, Integer, Boolean, Single, Double, Pointer, and Variant.

What are the benefits of Win32/64 native code such as in Delphi over .Net?

Format the IF/Endif for easy reading. I have found this to be easy to read and follow:

To indent the structure and line up the parenthesis makes it, I feel, much easier to read.