Pascal

8 Articles

Remembering UCSD P-System, The Pascal Virtual Machine

April 21, 2025 by 22 Comments

Long before the Java Virtual Machine (JVM) was said to take the world by storm, the p-System  (pseudo-system, or virtual machine) developed at the University of California, San Diego (UCSD) provided a cross-platform environment for the UCSD’s Pascal dialect. Later on, additional languages would also be made available for the UCSD p-System, such as Fortran (by Apple Computer) and Ada (by TeleSoft), not unlike the various languages targeting the JVM today in addition to Java. The p-System could be run on an existing OS or as its own OS directly on the hardware. This was extremely attractive in the fragmented home computer market of the 1980s.

After the final release of version IV of UCSD p-System (IV.2.2 R1.1) in 1987, the software died a slow death, but this doesn’t mean it is forgotten. People like [Hans Otten] have documented the history and technical details of the UCSD p-System, and the UCSD Pascal dialect went on to inspire Borland Pascal.

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Tridora: A Full-Custom CPU Designed For Pascal

October 23, 2024 by 13 Comments

[Sebastian Lederer] has created Tridora: an unusual stack-based CPU core intended for FPGA deployment, co-developed with its own Pascal compiler. The 32-bit word machine is unusual in that it has not one but three stacks, 16-bit instruction words, and a limited ISA, more like those of the 8-bit world. No multiply or divide instructions will be found in this CPU.

The design consists of about 500 lines of Verilog targeting the Digilent Arty-A7 FPGA board, which is based around the Xilinx Artix-7 FPGA line. [Sebastian] plans to support the Nexys A7 board, which boasts a larger FPGA array but has less RAM onboard. The CPU clocks in at 83 MHz with four clock cycles per instruction, so over 20 MIPS, which is not so shabby for a homebrew design. Wrapped around that core are a few simple peripherals, such as the all-important UART, an SD card controller and a VGA display driver. On the software side, the Pascal implementation is created from scratch with quite a few restrictions, but it can compile itself, so that’s a milestone achieved. [Sebastian] also says there is a rudimentary operating system, but at the moment, it’s a little more than a loader that’s bundled with the program image.

The Tridora Gitlab project hosts the Verilog source, an emulator (written in Golang, not Pascal) and a suite of example applications. We see quite a few custom CPUs, often using older or less popular programming languages. Here’s an FPGA-based Forth machine to get you started. Implementing programming languages from scratch is also a surprisingly common hack. Check out this from-scratch compiler for the Pretty Laughable Programming language.

Compiling And Running Turbo Pascal In The Browser

April 17, 2024 by 15 Comments

When a friend of [Lawrence Kesteloot] found a stack of 3.5″ floppy disks, they found that it contained Turbo Pascal code which the two of them had worked on back in the Summer of 1989. Amidst reminiscing about the High School days and watching movies on VHS, [Lawrence] sought a way to bring these graphical applications once more back to life. Not finding an easy way to compile Turbo Pascal code on Mac even back in 2013 when he started the project, he ended up writing a Turbo Pascal compiler in JavaScript, as any reasonable person would do in this situation.

SPIDER.PAS in its full glory. (Credit: Lawrence Kesteloot)
SPIDER.PAS in its full glory. (Credit: Lawrence Kesteloot)

As noted by [Lawrence], the compiler doesn’t implement the full Turbo Pascal 5.5 language, but only the subset that was required to compile and run these applications which they had found on the floppy disks. These include ROSE.PAS and SPIDER.PAS along with three others, and can also be found in the GitHub repository. As can be seen in the online version of the compiler, it captures the feel of programming Pascal in 1989 on the command line.

Naturally, the software situation has changed somewhat over the last decade. We’ve recently seen some promising multi-platform Pascal compilers, and of course you could even run Turbo Pascal in DOSBox or similar. That might make this project seem irrelevant, but being able to write and run Pascal applications in more ways and on more platforms is never a bad thing.

Developing In Pascal On The Commodore 64 With Abacus Super Pascal 64

February 14, 2024 by 8 Comments
Abacus Super Pascal 64 for the Commodore 64.

Most people associate the Commodore 64 with Commodore BASIC and precompiled applications, but it also had a number of alternative development environments produced for it. One of these was Super Pascal 64 by Abacus. A solid introduction to this software package is provided in a video tutorial by [My Developer Thoughts] on YouTube. This uses the Abacus Super Pascal 64 software and manual from the [Lyon Labs] website, which incidentally has a lot more development environments and operating systems for the C64 listed for your perusal.

Abacus’ Super Pascal supports the official Pascal language, requiring nothing more than a Commodore 64 and two Commodore 1541 floppy disk drives to get started. One FDD is for the Super Pascal software, which boots into the development environment, the other FDD and the disks in it are the target for the current project’s source code and compiled binary. Although the lack of support for FDDs other than the 1541 is somewhat odd, this comes presumably from the operating system nature of the development environment and the 1541 being by far the most common FDD for the C64.

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Niklaus Wirth with Personal Computer Lilith that he developed in the 1970ies. (Photo: ETH Zurich)

Remembering Niklaus Wirth: Father Of Pascal And Inspiration To Many

January 5, 2024 by 33 Comments

Although perhaps not as much of a household name as other pioneers of last century’s rapid evolution of computer hardware and the software running on them, Niklaus Wirth’s contributions puts him right along with other giants. Being a very familiar face both in his native Switzerland at the ETH Zurich university – as well as at Stanford and other locations around the world where computer history was written – Niklaus not only gave us Pascal and Modula-2, but also inspired countless other languages as well as their developers.

Sadly, Niklaus Wirth passed away on January 1st, 2024, at the age of 89. Until his death, he continued to work on the Oberon programming language, as well as its associated operating system: Oberon System and the multi-process, SMP-capable A2 (Bluebottle) operating system that runs natively on x86, X86_64 and ARM hardware. Leaving behind a legacy that stretches from the 1960s to today, it’s hard to think of any aspect of modern computing that wasn’t in some way influenced or directly improved by Niklaus.

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Turbo Rascal Is The Retro Pascal Compiler We Always Wanted

November 30, 2021 by 16 Comments

Pascal is not one of the biggest programming languages these days; it’s fallen into the background as the world moved on to newfangled things like C#, Python and Java. However, the language has its fans, one of whom put together a new compiler which targets retro platforms – and it goes by the name Turbo Rascal.

The list of supported platforms is extensive, with Turbo Rascal able to compile highly-optimized binaries for the C64, Amiga 500, BBC Micro, IBM PC, Atari ST, Game Boy, Amstrad, NES, ZX Spectrum, and more. There’s a usable IDE and even an included graphics editor for getting projects put together quickly. Also known by its full name of Turbo Rascal Syntax Error, or TRSE, it’s the work of one [Nicolaas Groeneboom].

The compiler runs on 64-bit Windows, Linux, and OS X, and there are extensive tutorial videos available on YouTube, too. Thus, there’s no excuse not to start developing a new retro game immediately. Check out the demo video below, and remember – as long as we keep using it, Pascal isn’t dead!

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No Pascal, Not A SNOBOL’s Chance. Go Forth!

November 3, 2015 by 47 Comments

My article on Fortran, This is Not Your Father’s FORTRAN, brought back a lot of memories about the language. It also reminded me of other languages from my time at college and shortly thereafter, say pre-1978.

At that time there were the three original languages – FORTRAN, LISP, and COBOL. These originals are still used although none make the lists of popular languages. I never did any COBOL but did some work with Pascal, Forth, and SNOBOL which are from that era. Of those, SNOBOL quickly faded but the others are still around. SNOBOL was a text processing language that basically lost out to AWK, PERL, and regular expressions. Given how cryptic regular expressions are it’s amazing another language from that time, APL – A Programming Language, didn’t survive. APL was referred to as a ‘write only language’ because it was often easier to simply rewrite a piece of code than to debug it.

Another language deserving mention is Algol, if only because Pascal is a descendant, along with many modern languages. Algol was always more popular outside the US, probably because everyone there stuck with FORTRAN.

Back then certain books held iconic status, much like [McCracken’s] black FORTRAN IV. In the early 70s, mentioning [Nicolas Wirth] or the yellow book brought to mind Pascal. Similarly, [Griswold, (R. E.)] was SNOBOL and a green book. For some reason, [Griswold’s] two co-authors never were mentioned, unlike the later duo of [Kernighan] & [Ritchie] with their white “The C Programming Language”. Seeing that book years later on an Italian coworker’s bookshelf translated to Italian gave my mind a minor boggling. Join me for a walk down the memory lane that got our programming world to where it is today.

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