0xCAFEBABE & 0xFEEDFACE

I'm surprised they didn't use 0xDECAFBAD for the Java format.

Even more interesting is the Wikipedia page https://en.wikipedia.org/wiki/Hexspeak catalogs a delightfully long list of hexspeak words and what they're used for.

Semi-related story with some insider baseball:

There are quite a few memorable words you can spell using 32 or 64 bits—like BA5EBA11. This is the story of me -not- choosing one of those.

These bit-pattern words are handy because they’re easy to recognize, especially in a random memory dump.

On my first “real” assignment, I was writing real-time embedded C code for a 16-bit processor that communicated with a host microprocessor on a server. We needed to run periodic assurance tests across a bus to ensure reliable communication with the host since we weren't constantly using the bus.*

We were given an unused register address on the host processor and told to write whatever we wanted to it. The idea was to periodically write a value, read it back, and if we encountered any write errors, incorrect reads, or failures, we’d declare a comm error and degrade the system in a controlled manner.

Instead of using zeros or something like 0xDEADBEEF, I decided to write 0x4D494B45 - "MIKE" in ASCII. It was unique, unlikely to be tampered with, it worked, and no one argued with me. The code shipped, the product shipped, and all was well. We even detected legitimate hardware errors, which I thought was pretty cool.

Fast forward two generations of systems, and long after I’d moved on from that team, the code had been ported around but that assurance test remained unchanged. Everything was fine until they brought up a new generation of systems, flipped on the firmware for that device, and 10 seconds later, my assurance test clobbered an important register. The entire system promptly checkstopped and crashed. It took the team days to figure out what was wrong, and I had to explain myself when they found "MIKE" staring back at them from the memory dump.

That was a fun project. ;-)

* Note: It would've been bad if our device went out to lunch because we were responsible for energy management of the server. If the power budget was exceeded and we couldn't downclock and downvolt the processor, something might have crashed or been damaged.

A side benefit of the 2GB address space limit for 32-bit Windows programs is that magic numbers are not valid pointers, and will instantly cause an access violation if used.

My preferred way to make a "magic" constant has been using base64. For example, 0x31a82270 maps to base64 `MagicA==`. This approach is most useful when the magic constant itself shouldn't be obviously ASCII but still should be meaningful enough.

Rust will yell at you if you use specific magic numbers like these

edit: yes, 0xCAFEBABE is a warning but 0xFEEDFACE is not:

3405691582

https://github.com/rust-lang/rust/blob/d0ea1d767925d53b2230e...

0x08675309 also shows up fairly often.

Welp, time to trademark the old handle.

a long time a go I wrote a script that spit out random phrases in hex that would work as a mac address. I used to do this to mess with my coworkers in networking , and previous coworkers at the ISP I was still using. My HN username is the only one i remember though.

0xC05FEFE

What about 0xDEADBEEF?

Great to see these UserLand Radio Blogs are still hosted all these years later. Dave Winer (and I am sure others) obviously worked to see that happen.

= CAECBA8E

0xDDDB00B5