Editor-Surveyor ‘splained it pretty well; now I beg leave to be pedantic.
“CMOS” Stands for Complementary Metal Oxide Semiconductor, and is the basic way that almost all low-power ICs are made.
So somewhere on your motherboard is a small-capacity RAM (Random Access Memory) chip which holds various setup data for your PC. Usually you don’t havee to be concerned with it, unless you’re a geek. The full description of this little memory is “CMOS static RAM.” Somewhere nearby is a small coin-shaped cell in a holder, which can sustain that memory chip’s contents for years. This makes it by definition “non-volatile.”
In contrast, your computer’s gigabytes of main memory, while also in CMOS technology, are “dynamic” RAM. This type is volatile, meaning that its contents are lost when the computer is turned off.
Why not have the main RAM be of the static type? Because the individual cells of static RAM are much larger than those of the dynamic type; a gigabyte of nonvolatile CMOS RAM would be prohibitively expensive, unless you’re NASA.
Why not have a battery big enough to hold up the contents of the main dynamic RAM during power off, and dispense with the static RAM? Because it would take too much power for extended power-off periods. Thus, the mix of a little static RAM and a whole lot of dynamic RAM has been the norm for laptops for a long time. (This paradigm has shifted with the advent of smarphones and tablets.)
Colloquially, in PC circles the nonvolatile static CMOS RAM is simply called “the CMOS,” even though the main, dynamic RAM is also technically CMOS.
I hope that my dilatory clarification has not had the vexing side effect of making the subject completely incomprehensible.
Please, if you would, direct the rest of us to the place where we can study to become geeks.
Der Prinz when to the University of Tennessee to become a geek.
Thank you, Erasmus, for the explanation. I kind of understood it a little bit! I still don’t know if all the games are gone, because I haven’t let #3 daughter use the computer since the Deletion occurred.