Dr. Brian Robert Callahan

Writing a code generator for our PL/0 compiler.

Building a simple automated testing framework for our PL/0 compiler.

Writing a parser for our PL/0 compiler.

Writing a complete lexer for our PL/0 compiler.

The beginning of a new series where we will write a simple PL/0 to C compiler from scratch.

Walking through my first OpenBSD port from ten years ago and revising it to today's standards.

An amateur radio musing on how you can further the state of the art.

Demonstrating lots of assembly language tricks to optimize for size.

Step-by-step how I thought through and wrote a moderately difficult OpenBSD port for the TIC-80.

A detailed tour of a CP/M and MS-DOS linker and object file format of our own creation.

Discussing a new hit program developed 40 years too late.

Porting a Unix program to MS-DOS for fun.

A how-to on basic profiler usage, improving the performance of our assembler.

Compiling the GNU D Compiler to OpenBSD/armv7.

Walking through how I ported the GNU D Compiler to OpenBSD/arm64.

Building a Brainfuck compiler with backends for amd64, i386, Z80 and C.

Part 9, Finishing our assembler with some pseudo-ops.

Part 8, teaching the assembler about logical shifts, incrementers and decrementers, and the lxi and mvi instructions.

Part 7, teaching the assembler about push, pop, jump/call/ret instructions.

Part 6, teaching the assembler about mov and arithmetic instructions.

Part 5, translating nop assembly instructions into 0x00 bytes.

Part 4, turning lines of Intel 8080 assembly language into their individual tokens.

Part 3, understanding assembler passes and setting up our error handler.

Part 2, planning the Z80 assembler.

Part 1 of a new series in which we create an assembler and disassembler for the Z80 CPU.

Discussing the process of getting a working gm2 on OpenBSD.

A detailed demonstration of a D screenshot utility from zero to complete.

The (condensed) story of how I got the GNU D Compiler working on OpenBSD.

Quick plug for my talk at BSidesROC 2021.

Presented in a table.

The story of how the Tiny C Compiler got ported to OpenBSD, from my perspective.

Explore how to leverage standard interfaces to create truly portable programs.

A look at a new programming language, Cowgol, designed for 8-bit CPUs.

A free article to inspire you to share your ham radio adventures.

Sharing my dream with you.

How I managed to do the ham radio hobby "wrong."

Introducing a new series in which we will learn how to design and implement a data transmit and receive protocol.

What I gained by shrinking my world.

I wrote the absolute minimum that could possibly be considered a text editor.

I hand-compiled some C code to see if I could do better than my C compiler.

Have you ever wondered how Unix programs know what argc and argv are?

Comparing compiler numbers, then discarding them as a distraction.

A very deep dive into a very small codebase.

Explaining my motivations for writing my newest Free Software project.

I decided to play the intro CTF to TryHackMe in order to begin to get a feel for how people think about cybersecurity pedagogy.