Depending on how far back you go in computer lore, you can find more than one definition of PRAM. The first is a Macintosh-only kind of internal computer memory. The second is more modern and, actually, still experimental.
PRAM in Mac land stands for Parameter random access memory (RAM), which is a kind of non-volatile RAM (NVRAM). PRAM contains a suite of very important information, including settings for a computer's startup disk and startup volume, time zone, and speaker volume. Previous versions of the Mac Operating System stored display and network settings in the PRAM. Mac OS X has eliminated that function, so users who have problems with network or display settings must reset PRAM.
The problem with resetting PRAM is that the procedure restores the machine to its factory defaults. Users who like to personalize their machines down to the last detail will find themselves spending quality time recreating all manner of settings. Still, the alternative is worse.
PRAM on a Macintosh is similar to complementary metal oxide semiconductor (CMOS) on a Windows machine. NVRAM is better known as the basis of Flash memory, which is currently dominating the portable electronics market, powering iPods, mobile phones, and digital cameras. None of these devices has PRAM, however.
The other meaning of PRAM, the one that is more modern and experimental, is Phase-change RAM. This kind of PRAM is expected to be the Flash of the next generation. It can rewrite data on a chip without having to erase all the data that is already on the chip. That's a significant improvement over NOR Flash memory chips, which still rely on the tried-and-true two-step of Delete, Then Write.
Phase-change RAM is the idea behind rewritable CDs and DVDs and what makes them such a speedy solution for repeated storage of data. It's all about speed and processing power, and this kind of PRAM delivers both. The other benefit to this kind of PRAM is a lower processing power requirement. By eliminating the Erase-first stage in the data transfer process, Phase-change RAM requires less energy as well. Less power, less time: what's not to love?
This kind of PRAM is expected to be available in the next few years. It has higher capacities and a longer shelf life than the NOR Flash of today. As expected, the giants of the chipmaking world, including Intel and Samsung, are pursuing breakthroughs in this field.