General Development Archive

Cidco MailStation as a Z80 development platform

The Cidco MailStation is a series of dedicated e-mail terminals sold in the 2000s as simple, standalone devices for people to use to send and receive e-mail over dialup modem. While their POP3 e-mail functionality is of little use today, the hardware is a neat Z80 development platform that integrates a 320×128 LCD, full QWERTY keyboard, and an internal modem. After purchasing one (ok, four) on eBay some months ago, I’ve learned enough about the platform to write my own software that allows it to be a terminal for accessing BBSes via its modem or as a terminal for a Unix machine connected over parallel cable. A year old story, but come on, this is timelessly cool.

Dropbox’s journey to type checking 4 million lines of Python

Dropbox is a big user of Python. It’s our most widely used language both for backend services and the desktop client app (we are also heavy users of Go, TypeScript, and Rust). At our scale—millions of lines of Python—the dynamic typing in Python made code needlessly hard to understand and started to seriously impact productivity. To mitigate this, we have been gradually migrating our code to static type checking using mypy, likely the most popular standalone type checker for Python. (Mypy is an open source project, and the core team is employed by Dropbox.) This post tells the story of Python static checking at Dropbox, from the humble beginnings as part of my academic research project, to the present day, when type checking and type hinting is a normal thing for numerous developers across the Python community. It is supported by a wide variety of tools such as IDEs and code analyzers. I recently came across an article complaining about Python’s dynamic typing and couldn’t quite believe this was still the case. As it turns out, nowadays there is indeed a standardized way to do write type annotations and to type-check prior to runtime using mypy, all the while being driven forward by the good folks at Dropbox (which includes Python’s Benevolent Dictator for Life Guido van Rossum). This article provides a fascinating insider insight into the history of type-checking in Python and how it evolved in symbiosis with Dropbox’s codebase.

Zip files: history, explanation, and implementation

I have been curious about data compression and the Zip file format in particular for a long time. At some point I decided to address that by learning how it works and writing my own Zip program. The implementation turned into an exciting programming exercise; there is great pleasure to be had from creating a well oiled machine that takes data apart, jumbles its bits into a more efficient representation, and puts it all back together again. Hopefully it is interesting to read about too. This article explains how the Zip file format and its compression scheme work in great detail: LZ77 compression, Huffman coding, Deflate and all. It tells some of the history, and provides a reasonably efficient example implementation written from scratch in C. One for the ages. Articles like this don’t get written every day.

A deep dive into the Apollo Guidance Computer, and the hack that saved Apollo 14

Under hard time pressure, the ground had to quickly figure out what was wrong and devise a workaround. What they came up with was the most brilliant computer hack of the entire Apollo program, and possibly in the entire history of electronic computing. To explain exactly what the hack was, how it functioned, and the issues facing the developers during its creation, we need to dig deep into how the Apollo Guidance Computer worked. Hold onto your hats, Ars readers—we’re going in. Amazing story.

Wine 5.0 released

This release represents a year of development effort and over 7,400 individual changes. It contains a large number of improvements that are listed in the release notes below. The main highlights are: – Builtin modules in PE format.– Multi-monitor support.– XAudio2 reimplementation.– Vulkan 1.1 support. Wine allows me to run virtually any Windows game I use on Linux – including League of Legends, my most-played game – so it’s a pretty amazing tool in my book. Since many people no longer directly interact with Wine, using it through tools like Steam’s compatibility tools or Lutris, instead, it’s easy to forget just how important of a project Wine really is.

A walk through the Magit interface

This article demonstrates some of Magit’s most essential features in order to give you an impression of how the interface works. It also hints at some of the design principals behind that interface. But this is only the tip of the iceberg. Magit is a complete interface to Git, which does not limit itself to the “most essential features everyone needs”. I hope that this article succeeds in demonstrating how Magit’s focus on work-flows allows its users to become more effective Git users. Here we concentrate on some essential work-flows, but note that more advanced features and work-flows have been optimized with the same attention to detail. If you would rather concentrate on the big picture, then read the article Magit the magical Git interface instead (or afterwards). As a non-developer, I have no idea if this is a useful tool, but I do like the idea of it.

Tearing apart printf()

If ‘Hello World’ is the first program for C students, then printf() is probably the first function. I’ve had to answer questions about printf() many times over the years, so I’ve finally set aside time for an informal writeup. The common questions fit roughly in to two forms: Easy: How does printf mechanically solve the format problem?Complex: How does printf actually display text on my console? My usual answer? “Just open up stdio.h and track it down” This wild goose chase is not only a great learning experience, but also an interesting test for the dedicated beginner. Will they come back with an answer? If so, how detailed is it? What IS a good answer? This is incredibly detailed and definitely over my head, but I’m sure many of you will enjoy this one greatly.

Making a RISC-V operating system using Rust

RISC-V (“risk five”) and the Rust programming language both start with an R, so naturally they fit together. In this blog, we will write an operating system targeting the RISC-V architecture in Rust (mostly). If you have a sane development environment for RISC-V, you can skip the setup parts right to bootloading. Otherwise, it’ll be fairly difficult to get started. This tutorial will progressively build an operating system from start to something that you can show your friends or parents — if they’re significantly young enough. Since I’m rather new at this I decided to make it a “feature” that each blog post will mature as time goes on. More details will be added and some will be clarified. I look forward to hearing from you! Always wanted to to code your own operating system? This tutorial series shows how to create a simple operating system for RISC-V using Rust as your programming language. Currently the two first chapters are available. The code is also available on Github.

LLVM 9.0.0 released

This release is the result of the LLVM community’s work over the past six months (up to trunk r366426 plus commits on the branch). Some highlights include: – Support for asm goto, enabling for example the mainline Linux kernel for x86_64 to build with Clang – The RISCV-V target is no longer experimental, but built by default – Experimental support for C++ for OpenCL As well as many bug fixes, optimizations, and diagnostics improvements. Read the release notes for the detailed information.

Visible Lisp Computer

The Visible Lisp Computer is a Lisp interpreter that displays the contents of the Lisp workspace on an OLED display, so you can see program execution and garbage collection in real time. It’s a special version of my uLisp interpreter for ARM boards, designed to run on an Adafruit ItsyBitsy M0, or an ATSAMD21E on a prototyping board, interfaced to an I2C OLED display. If I knew what any of this meant, you’d find a few words about this here. Sadly, I don’t know what any of this means.

Flutter looks good, but is painful. Here are my frustrations with it.

From the community to the 3rd party libraries, it looks Flutter is lot closer to Javascript than Android. Javascript, however, isn’t shy of moving faster while Flutter is still deciding what they want to be. Keep compatibility even if it creates confusion? Check. A lot of libraries with dubious quality that are just created and dropped? Check. I want to like it, but Flutter currently doesn’t want to like me. Maybe they are are short in personnel and needs to double their team? Maybe they need to just re-organize and prioritise better? Only they know. Not being a programmer in any way, shape, or form, articles such as these are always difficult to gauge – are they truthful? Factual? Emotional? My-way-or-the-highway? I’m posting it anyway since I’m sure many of you have a far better grasp on this than I do.

Jupiter: a RISC-V assembler and runtime simulator

Jupiter is an open source and education-oriented RISC-V assembler and runtime simulator. It is written in Java 11 and capable of simulate all the instructions of the base integer ISA (I extension) plus the M and F extensions (RV32IMF), including all the pseudo-instructions described in the user-level instruction set manual. It was developed taking into account that it could be used in various courses such as: Computer Architecture, Compilers and Assembly Programming.

Fast software, the best software

I love fast software. That is, software speedy both in function and interface. Software with minimal to no lag between wanting to activate or manipulate something and the thing happening. Lightness. Software that’s speedy usually means it’s focused. Like a good tool, it often means that it’s simple, but that’s not necessarily true. Speed in software is probably the most valuable, least valued asset. To me, speedy software is the difference between an application smoothly integrating into your life, and one called upon with great reluctance. Fastness in software is like great margins in a book — makes you smile without necessarily knowing why. Nothing to add.

Files are fraught with peril

In this talk, we’re going to look at how file systems differ from each other and other issues we might encounter when writing to files. We’re going to look at the file “stack” starting at the top with the file API, which we’ll see is nearly impossible to use correctly and that supporting multiple filesystems without corrupting data is much harder than supporting a single filesystem; move down to the filesystem, which we’ll see has serious bugs that cause data loss and data corruption; and then we’ll look at disks and see that disks can easily corrupt data at a rate five million times greater than claimed in vendor datasheets. Deeply technical, but well-written and pleasant to read.

Pete’s QBasic site

QBasic lives! QBasic is an old-school, vintage programming language that was designed for beginners. QBasic ran on MS-DOS, and was a more advanced version of BASIC. QB was a lot of people’s first foray into programming (particularly those of us who grew up in the ‘80s and ‘90s). Therefore, a lot of people look back at QBasic with nostalgia. QBasic is one of the very few programming languages I actually ever even used – back when i was a very young kid – so I do have some faint nostalgia for it. Great to see such a dedicated community keeping it alive.

GCC 9.1 released

GCC 9.1 is a major release containing substantial new functionality not available in GCC 9.x or previous GCC releases. In this release C++17 support is no longer marked experimental. The C++ front-end implements the full C++17 language (already previous GCC major version implemented that) and the C++ standard library support is almost complete. The C++ front-end and library also have numerous further C++2a draft features. GCC has a new front-end for the D language. GCC 9.1 has newly partial OpenMP 5.0 support and almost complete OpenACC 2.5 support.

Game Boy CPU manual

This document was designed to help you programming the Game Boy Classic, Game Boy Pocket, Super Game Boy and Game Boy Color (basics – you will need additionaldocuments for GBC specific programming). It was ment to be a complete handbook to start right off coding forthe hardware. The documents consists of three major parts. The first is the ‘GBSpec.txt’ (also known as the Pan Document) by Pan of Anthrox, Marat Fayzullin, Pascal Felber, Paul Robson, Martin Korth, kOOPa. This will be found in paragraph 1. The second is a mixture of several documents from ‘Game Boy Assembly Language Primer (GALP) V1.0’ by GABY (GAmeBoY). It contains opcodes, time duration and the affected flags per ASM command and the. This can befound in paragraph 2. The third is a summary of specifications and commands for Nintendo Super Game Boy speciffic programming bykOOPa and Bowser. See paragraph 3. Some light reading to kick off the week.