TL;DR? I saw “256GB ROM” in a phone’s website and thought that where we store data were ROM devices. It happens Hard disk and relatives are not ROMS.
In: Technology
I suggest you read this site:
https://www.geeksforgeeks.org/random-access-memory-ram-and-read-only-memory-rom/
It gives a proper and easy to understand overview as you clearly are confusing a couple of things
Because you cant. ROM contains the core processing system besides other things, you you cant put stuff onto it, your computer has other memory for putting things on.
ROM is used for ultra long term storage. It may be writable, but its not written to under normal circumstances.
In your computer, the BIOS software will be stored on ROM along with any settings. If you flash your BIOS to a new version it will write to the ROM but you might write to that ROM just a few times over the life of the computer which is good because the ROM can probably only tolerate on the order of thousands of writes before it breaks.
RAM and other storage like HDDs and SSDs are read and written to thousands to billions of times per hour. RAM has no write limitation, you can write to RAM trillions of times and it will keep working just as well as it always has.
While you *can* write to certain types of ROM, you generally don’t write to ROM
You may be speaking to RAM. RAM is Random Access Memory and is designed to respond quickly to arbitrary requests for data.
It is more compact and historically more expensive than writing data to a hard disk.
ROM is still Read Only Memory. It is used to preserve data, settings, and routines that may be damaged in undesired ways if the host operating system begins to fail; in this way, you can restore the bios or operating system.
Read Only Memory is only permanently read only when set up at the hardware level. It is possible for memory to be read only in some contexts but not in others.
E.g., an administrator may set up security programs that a user cannot overwrite or override. However, those programs still need to be updated with some regularity. An administrator may have sufficient permissions to push an update while the user cannot.
ROM (Read-only Memory) is like a published book. It already has words (data) on it when you get it from the store, and those words are printed in a way as to make them permanent (ie. you can’t just take an eraser and rub out the words.)
*But*, if you had your own printing press, you could potentially take the pages from the book and use your equipment to print over the existing words. First you print a “blank” page (erasing everything that was written on it before), then you print whatever you want over the blank. Do it well enough, and you can treat it as if the book was always like that.
When we do this to ROM, it’s called “flashing”. Modern ROM often comes with its own miniature “printing press” embedded in it, and it’s called “Flash ROM” or “EEPROM” (Electronically Erasable/Programmable Read-only Memory). USB Flash drives are composed from thousands of tiny Flash ROM modules, hence the name.
It’s called ROM because for all intents and purposes, it behaves like a pre-printed book. It just happens to come with its own printing press.
The other type of memory is called RAM (Random-access Memory). This memory is more like a blank notebook that you write on with a pencil. You can erase whatever little bits of writing you want, without affecting other bits. And every time you close the notebook, everything written inside it gets erased.
I have seen it become increasingly common for generic devices (particularly Android TV boxes) to use the term ROM to refer to solid state storage, differentiating it from RAM, which is the devices memory.
It is an incorrect use of the term – ROM is unerasable data, as others have pointed out. Back in the old days of CDs, they were called CD-ROMs, because once written, they couldn’t be changed, so it was Compact Disk – Read Only Memory.
It was caused by electronic evolution and naming inertia. Most people don’t even notice it (or know about it). **Good job, OP!**
In the early days of integrated circuits, people invented true ROMs (Read Only Memories). The data they contained was instantiated inside of them during manufacturing, and there was no way for anyone to change it. Hence they were “read only”. They could only be “written” once, at the factory that made them. Made perfect sense.
Then PROMs were invented. A Programmable Read Only Memory was blank when shipped out (full of 0s). They could be programmed once, essentially blowing tiny fuses within the device. Once you turned a 0 into a 1 it was never going back. Kind of like making toast, but not as tasty. You could actually program them again, so long as you were OK with all the 1s staying 1s. But you could turn more 0s into 1s if you wanted. Obviously, these devices weren’t quite truly “read only”, since you could write them at least once. But otherwise they would behave like a ROM, so the name was reasonably apt.
Then came EPROMs. Erasable Programmable Read Only Memories. They acted like PROMs. Except they had a glass window over the chip and if you exposed a programmed device to ultraviolet light for a while, the programming would be erased, and the part would be back to all 0s. (These didn’t use tiny fuses any more.) So they kind of behaved like PROMs, which were kind of like ROMs. But if you did something weird (UV light exposure) they could be erased and re-programmed. Not really “read only”, but sorta. So the acronym still stuck, even though it wasn’t technically true. This is where the nomenclature started going off the rails.
Then came EEPROMs. These Electrically Erasable Programmable Read Only Memories could be erased with an electrical signal, not UV light. (UV light usually worked too, but the window was no longer present so it was kind of a moot point for people without nitric acid to etch open the plastic package.) The device acted kind of like an EPROM, which was sort of like a PROM, which behaved quite a bit like a ROM. So the name stuck, even though it mde no damned sense any more. If it’s electrically erasable, and programmable, it’s obviously not “read only”. But in a circuit it could still fulfill the function that a ROM used to fulfill, albeit with more flexibility. So the dumb name stuck.
And that’s how we got where we are today.
In something like a phone, what the manufacturer calls a ROM could be almost any of those devices. Although probably not an EPROM, since those are a bit rare these days. They call it a ROM to differentiate it from other kinds of memory in the phone that apps can write to, such as RAM or Flash EEPROM.
**P.S.** Things like hard disc drives (HDDs), solid state drives (SSDs), DRAMs (Dynamic Random Access Memories), and SRAMs (Static Random Access Memories) are not ROMs and have never been considered ROMs. They are different things, even though they are all memory devices.
Flash memory is an EEPROM with a specific configuration that makes it denser/cheaper, but puts some limitations on how it can be erased.
The phone’s website is technically wrong. They just mean that it has 256GB of storage. The operating system is installed to memory that holds up to 256GB. Like how if you bought a home computer in the 80s or 90s it would say “64K ROM” or something. It would have 64K worth of ROM chips installed, which would contain the OS.
It’s sort of like how if you have an SSD in your computer, you can still “save something to disk”. There’s no disk. The language is just based on older technology that does the same basic thing but in a different way.
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