programming-for-all-pascal

Chapter 1: Introduction to Pascal

History and Background

Pascal is a procedural programming language designed by Niklaus Wirth in the late 1960s. It was named after the French mathematician and philosopher Blaise Pascal. The language was designed to encourage good programming practices using structured programming and data structuring.

Pascal was originally developed as a teaching tool but quickly became popular in industry for its clarity and ease of use. It has influenced many other programming languages, including Ada, Modula-2, and even early versions of the influential language Delphi.

Getting Started with Pascal

To start programming in Pascal, you will need a Pascal compiler. Some popular Pascal compilers include:

• Free Pascal (FPC): An open-source compiler that supports various Pascal dialects and is available on multiple platforms.
• Turbo Pascal: An older but historically significant compiler developed by Borland.
• Lazarus: An open-source integrated development environment (IDE) for Free Pascal.

Installing Free Pascal

Here are the steps to install Free Pascal on different operating systems:

Windows

1. Download the Free Pascal installer from the official website.
2. Run the installer and follow the on-screen instructions.
3. Once installed, open the command prompt and type fpc to check if the installation was successful.

macOS

1. Download the Free Pascal installer from the official website.
2. Open the downloaded .dmg file and drag the Free Pascal application to your Applications folder.
3. Open Terminal and type fpc to verify the installation.

Linux

1. Open your terminal.
2. Use your package manager to install Free Pascal. For example, on Debian-based systems, you can use:

   sudo apt-get install fpc
   

3. Type fpc in the terminal to ensure it’s installed correctly.

Writing Your First Program

Let’s write a simple program in Pascal to get started. This program will print “Hello, World!” to the console.

Create a new file called hello.pas and add the following code:

program HelloWorld;
begin
  writeln('Hello, World!');
end.

Explanation

• program HelloWorld; declares the name of the program.
• begin and end. mark the beginning and end of the program’s main block.
• writeln('Hello, World!'); is a built-in procedure that writes the specified string to the console.

Compiling and Running the Program

Using the Command Line

1. Open your command line interface (CLI).
2. Navigate to the directory where you saved hello.pas.
3. Compile the program using the Free Pascal Compiler:

   fpc hello.pas
   

4. If there are no errors, this will create an executable file named hello.
5. Run the executable:

   ./hello  # On Windows, use hello.exe
   

You should see Hello, World! printed on the console.

Congratulations! You’ve written and run your first Pascal program. In the next chapters, we’ll dive deeper into Pascal’s syntax, data types, and control structures.

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