This document will explain the basics about compilers as well as provide links to well-known Pascal compilers and explain how to set up Free Pascal.
When talking about computer languages, there are basically three major terms that will be used.
Microprocessors can only run machine language programs directly. Assembly language programs are assembled, or translated into machine language. Likewise, programs written in high-level languages, like Pascal, must also be translated into machine language before they can be run. To do this translation is to compile a program.
The program that accomplishes the translation is called a compiler. This program is rather complex since it not only creates machine language instructions from lines of code, but often also optimizes the code to run faster, adds error-correction code, and links the code with subroutines stored elsewhere. For example, when you tell the computer to print something to the screen, the compiler translates this as a call to a pre-written module. Your code must then be linked to the code that the compiler manufacturer provides before an executable program results.
With high-level languages, there are again three basic terms to remember:
The de facto standard in DOS and Windows-based compilers is Borland Pascal. Before it came out, most Pascal compilers were clumsy and slow, strayed from the Pascal standard, and cost several hundred dollars. In 1984, Borland introduced Turbo Pascal, which sold for less than $100, compiled an order of magnitude faster than existing compilers, and came with an abundance of source code and utility programs.
This product was a great success and was prominent for almost a decade. But in the 1990s, the world was moving to Windows. In 1993, the last version of Turbo Pascal, version 7 for DOS, came out. After that, the demand for DOS programs plummetted and Borland (renamed Inprise, then back to Borland) focused on producing Windows compilers.
This tutorial will only deal with console-based programming, where the computer prints lines of data to the screen and the user interacts with the program using a keyboard. The goal of the tutorial is to teach how to program in Pascal. Once you've learned that, you can easily look at a reference book or another web page and pick up graphics and windowing systems on your own.
Although old commercial Pascal compilers are often available for download, Turbo Pascal 5.5 from the Borland Museum and Symantec Think Pascal (Macintosh) linked from The Free Country's Free Pascal Compiler List, computers have progressed much since the 1980s and early 1990s. We are no longer stuck with 8.3 filenames on DOS or non-preemptive multitasking on Mac OS. Using an old compiler is fun in the same sense as playing an old game on an emulator, but the open source movement has produced good compilers for modern operating systems, and a beginner will find it much easier to use those.
Free Pascal is generally considered friendlier for novices, and strives to emulate Borland Pascal in many ways, though both will serve fine for learning Pascal. The easiest way for a novice to get started with Pascal programming is to download the Lazarus IDE, which provides a friendly, GUI-based environment for the Free Pascal compiler.
Here's how to get started, step by step, on Windows. Lazarus and Free Pascal are available on other operating systems too; some steps will differ slightly.
With programs that don't expect user input, you'll see a window flash up and disappear. This is because the program finishes running in the blink of an eye, and closes itself. You are returned to the IDE without seeing the results of your work. There are two ways around this:
We'll be learning only the fundamentals of Pascal in this tutorial, so we'll be sticking to console programs that print text to the screen and interact with the keyboard. However, Lazarus and Pascal are capable of producing programs as complicated as any that you have on your computer right now. A web browser? A spreadsheet? A game? All possible, with thousands (or millions!) of man-hours of effort.
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