NVRAM serves approximately the same purpose as PRAM, but instead of storing a dozen or more pieces of information, it now contains just a few: your selected startup disk, speaker volume, screen resolution, time zone, and-if your Mac has crashed recently-details of the last kernel panic. Modern Macs no longer use PRAM they instead use something called NVRAM (NV for non-volatile). So you could press a key sequence at startup to reset (or “zap”) the PRAM, returning it to default, factory values. If the values in this memory got out of whack for one reason or another, your Mac might not start up correctly or might exhibit any of numerous odd behaviors afterward. The P in PRAM stood for “parameter” (the RAM was just RAM-random access memory), and it referred to a small amount of special, battery-backed memory in every Mac that stored information the computer needed before it loaded the operating system.

Back in the day, the standard list of quick fixes for random Mac ailments always included clearing the PRAM.

Mac zapper