My journey to Lisp began in the early 1990s. Over three decades later, a few days ago I rediscovered the first Lisp environment I ever used back then which contributed to my love for the language. Here it is, PC Scheme running under DOSBox-X on my Linux PC:

Using PC Scheme again brought back lots of great memories and made me reflect on what the environment taught me about Lisp and Lisp tooling.

As a Computer Science student at the University of Milan, Italy, around 1990 I took an introductory computers and programming class taught by Prof. Stefano Cerri. The textbook was the first edition of Structure and Interpretation of Computer Programs (SICP) and Texas Instruments PC Scheme for MS-DOS the recommended PC implementation. I installed PC Scheme under DR-DOS on a 20 MHz 386 Olidata laptop with 2 MB RAM and a 40 MB hard disk drive.

Prior to the class I had read about Lisp here and there but never played with the language. SICP and its use of Scheme as an elegant executable formalism instantly fascinated me. It was Lisp love at first sight.

The class covered the first three chapters of the book but I later read the rest on my own. I did lots of exercises using PC Scheme to write and run them.

Soon I became one with PC Scheme.

The environment enabled a tight development loop thanks to its Emacs-like EDWIN editor that was well integrated with the system. The Lisp awareness of EDWIN blew my mind as it was the first such tool I encountered. The editor auto-indented and reformatted code, matched parentheses, and supported evaluating expressions and code blocks. Typing a closing parenthesis made EDWIN blink the corresponding opening one and briefly show a snippet of the beginning of the matched expression.

Paying attention to the matching and the snippets made me familiar with the shape and structure of Lisp code, giving a visual feel of whether code looks syntactically right or off. Within hours of starting to use EDWIN the parentheses ceased to be a concern and disappeared from my conscious attention. Handling parentheses came natural. I actually ended up loving parentheses and the aesthetics of classic Lisp.

Parenthesis matching suggested me a technique for writing syntactically correct Lisp code with pen and paper. When writing a closing parenthesis with the right hand I rested the left hand on the paper with the index finger pointed at the corresponding opening parenthesis, moving the hands in sync to match the current code. This way it was fast and easy to write moderately complex code.

PC Scheme spoiled me and set the baseline of what to expect in a Lisp environment.

After the class I moved to PCS/Geneva, a more advanced PC Scheme fork developed at the University of Geneva. Over the following decades I encountered and learned Common Lisp, Emacs, Lisp, and Interlisp. These experiences cemented my passion for Lisp.

In the mid-1990s Texas Instruments released the executable and sources of PC Scheme. I didn't know it at the time, or if I noticed I long forgot. Until a few days ago, when nostalgia came knocking and I rediscovered the PC Scheme release.

I installed PC Scheme under the DOSBox-X MS-DOS emulator on my Linux Mint Cinnamon PC. It runs well and I enjoy going through the system to rediscover what it can do.

Playing with PC Scheme after decades of Lisp experience and hindsight on computing evolution shines new light on the environment.

I didn't fully realize at the time but the product packed an amazing value for the price. It cost $99 in the US and I paid it about 150,000 Lira in Italy. Costing as much as two or three texbooks, the software was affordable even to students and hobbyists.

PC Scheme is a rich, fast, and surprisingly capable environment with features such as a Lisp-aware editor, a good compiler, a structure editor and other tools, many Scheme extensions such as engines and OOP, text windows, graphics, and a lot more. The product came with an extensive manual, a thick book in a massive 3-ring binder I read cover to cover more than once. A paper on the implementation of PC Scheme sheds light on how good the system is given the platform constraints.

Using PC Scheme now lets me put into focus what it taught me about Lisp and Lisp systems: the convenience and productivity of Lisp-aware editors; interactive development and exploratory programming; and a rich Lisp environment with a vast toolbox of libraries and facilities — this is your grandfather's batteries included language.

Three decades after PC Scheme a similar combination of features, facilities, and classic aesthetics drew me to Medley Interlisp, my current daily driver for Lisp development.

#Lisp #MSDOS #retrocomputing

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I'm looking for source code of MS-DOS .COM programs in real-mode 8086 Assembly written in NASM syntax.

Why such weird requirements? I'm learning Assembly programming under MS-DOS and MikeOS, and cross-developing on Linux with NASM. To avoid the complexity of x86 segmentation, I prefer to focus on single-segment programs as I plan to write small applications anyway. So I'd like to study examples of how these programs organize and reference data and code.

Despite the long history and influence of MS-DOS, finding .COM code is proving unexpectedly hard.

Googling doesn't turn up much. I solicited recommendations on comp.os.ms.dos.programmer, comp.lang.asm.x86, the NASM forum, and Mastodon but, aside from a lot of engagement and interest (and the occasional suggestion I change my mind and target Windows), I got few resources.

#Assembly #MSDOS #retrocomputing #x86

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Working on Suite8080 and using the Z80MBC2 encouraged me to learn Intel 8080 and Z80 Assembly.

Now I'm dipping my toes into x86 Assembly, which I've always been curious about and attracted by. An additional motivation is discovering MikeOS, a lovely real-mode operating system in x86 Assembly that's surprisingly easy to read and understand.

Therefore, I put together an environment to cross-develop and run x86 code.

Requirements

My desktop daily driver is an ASUS Chromebox 3, with the Crostini Linux container of chromeOS that lets me run most Linux software. Any emulation and development tools must therefore be available for Linux.

Intel x86 Assembly is close enough to 8080 Assembly that x86 code looks familiar. To leverage this similarity and avoid the complexity of x86 segmentation, for the time being I want to develop 16-bit real-mode programs that fit into the single segment of a .COM executable.

The obvious choice for an operating system to run these programs is MS-DOS. Why? Because its rich environment strikes the right balance between complexity and functionality.

So the emulator must run a full MS-DOS environment and boot from media images. Which enables coding for the bare metal, a PC with no operating system.

As for the Assembly tools, I prefer to cross-develop on Linux. Although I'm a retrocmputing enthusiast, for writing and building code I want the convenience of a modern system.

MS-DOS emulation

QEMU would have been my first choice for x86 emulation but has compatibility issues with Crostini, as virtualizing in a virtual environment is tricky.

A bit of research led me to DOSBox-X, which runs fine on Crostini as it emulates rather than virtualize. DOSBox-X is a fork of DOSBox with a more fleshed out MS-DOS environment. Plus it can boot from media images.

DOSBox-X running under chromeOS on my Chromebox looks like this:

Installing DOSBox-X on the Chromebox was straightforward. However, the Flatpak package carried almost a gigabyte worth of dependencies that nearly filled the Crostini file system. I had to resize the container from 7.5 to 10 GB to accommodate all the files and leave enough free space.

A feature I like is the emulator can mount a directory tree of the Linux file system as an MS-DOS disk. This is handy for quickly transferring cross-assembled binaries to MS-DOS.

DOSBox-X has rendering issues on chromOS, i.e. the menu bar and items flicker randomly. A workaround is to turn off the menu bar.

I tested DOSBox-X booting by checking out MikeOS, which runs well.

Assembly development

There's a vast assortment of x86 assemblers but I skipped the research by picking NASM for Linux.

I like this popular tool because it's rich of features and comes with extensive documentation. It also has a clean, non verbose syntax and can generate MS-DOS .COM programs.

To test the full cross-development and emulation toolchain I used NASM to assemble an x86 real-mode hello world demo, copied it to a directory DOSBox-X mounts as a disk, and ran it under MS-DOS. Success! A simple and low friction workflow.

#Assembly #MSDOS #chromeOS #retrocomputing #x86

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