Inspired by some comments on the question "The history of the NULL pointer":-
There was a practice in the '70s to use the hexadecimal code
0xDEADBEEF to indicate an invalid value. This could be to fill memory that was freed after a previous allocation, as the value of
NULL in C, or as an inaccessible address.
The use of DEADBEEF is said to have originated on IBM midrange machines, as an easily identifiable error code when looking at a hex dump. My experience of it is on VMS on DEC Vax machines, it allegedly was used on Apple Macs and the Commodore Amiga. However, I haven't encountered it in use for several years.
Quick searching throws up differing and contradictory stories as to its spread and usage, so...
Did IBM system engineers change jobs and take DEADBEEF with them as a code in other systems?
git grep -i deadbeef | wc -lprints 404. According to Wikipedia it’s also used to mark freed memory in Solaris.