PPC Journal was an early hobbyist computer magazine, originally targeted at users of HP's first programmable calculator, the HP-65. It originated as 65 Notes and the first issue was published in 1974. It later changed names in 1978 to PPC Journal and in 1981 to PPC Calculator Journal.
The founder of the PPC (Personal Programming Center) was Richard Nelson. This hobbyist group worked around the journal and was known because Nelson discovered hidden instructions on the HP-65 calculator. Later the club and the journal got maximum notoriety when several club members discovered the "synthetic instructions" of the HP-41C.
References
PPC Journal Wikipedia(Text) CC BY-SA