Getting Technical
Why are USB memory sticks also called flash drives?
Because the storage technology behind it is called flash memory. If you’re wondering what that means I can’t promise that you will be smarter at the end of this article. But what I can do is give you some textual and visual ideas. Latter is what I always find to be most helpful.
So at first a brief text definition. Flash memory is a type of EEPROM which stands for Electrically Erasable Programmable Read-Only Memory. It’s a non-volatile memory that can store little data chunks especially when there’s no power. When the chunks need to be larger the specific flash kind is used. In other words, usual EEPROM is only byte-erasable whereas Flash is block-erasable. I’m sure you already feel smarter or lost.
Ok, then let’s have a picture that shows the typical interior of a USB flash drive.
Source: Marhsall’s Brain Blog – I have four different memory sticks
What you see on the left is the chip that holds the actual flash memory and the chip on the right is called a microcontroller. The last part is just for your information and shall be of no interest regarding flash technology. So keeping focused on the left chip, inside it is an array of memory cells which themselves contain floating gate transistors. You can see one in the next image:
Source: ZDNet defintion for EEPROM
To quote above source, “The storage part of an EEPROM cell acts like a permanently-open or closed transistor. Charging is accomplished by grounding the source and drain terminals and placing a voltage on the control gate. When the “floating gate” is charged, it impedes the flow of electrons from the control gate to the silicon, and the 0 or 1 is determined by whether the voltage on the control gate is blocked or not.”
Uhm, ok. Now, 0 means a transistor is off and 1 means it’s on because the gate is open and electricity can flow. With a regular transistor the data would be lost once the power is turned off because that shuts down the whole thing and it stays in the 0 position even when power is back on. A flash memory cell however saves the data because it’s basically in a permanent 1 position. That’s due to its second gate, the floating gate, which enables electricity to stay trapped between it and the first gate. The data can still be erased though by draining the electricity out, that’s what the drain to the right is for.
I guess I could try to get into more detail now but to be honest, I really don’t understand most of this stuff. I just use these sticks and think they’re cool. What I’m left wondering is: Why is it actually called Flash? Is it just some fancy marketing phrase? Either way, if you want to get deeper and feel this urge to also know what a microcontroller is for I advise you to join a geek forum or sift through the tons of articles out there on the net. Then please come back and post an explanation. 
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April 30th, 2010 at 12:05 am
Electrically Erasable is a big deal. In the old days, memory had to be erased using a UV lamp. The parts had a window above the die. Those days are now thankfully past us.
Flash comes from the idea that entire part can be erased with one “flash” of the UV light.
May 3rd, 2010 at 1:02 am
Mike,
are you sure you mean UV light?
May 8th, 2010 at 1:40 am
Mike explained it correctly. It’s the ideas of erasing it “in a flash” regarding time.
July 15th, 2010 at 6:45 am
Hi DT, thanks for explaining USB related concepts in detail, I think I learned a lot.
October 25th, 2010 at 5:46 pm
if you describe flashing in one line….???
October 27th, 2010 at 2:38 am
Usman,
what do you mean “flashing”? To describe how a flash memory works I’d need more than one short line. Maybe somebody else can?
March 19th, 2011 at 12:38 am
Flash memory is probably the greatest invention of mankind for the last time. I do not even know how to look right now is an invention without such devices. Thanks to the author for a detailed explanation of the structure of flash memory. Now I felt that really became more aware of this.
March 25th, 2011 at 12:06 am
i dont know what a flash is and what it does – all i know is that students carry it around for nothing….LOL….
i think they shove it up peoples….
so BEWARE……
April 1st, 2011 at 9:38 am
It was nice learning about these small details.
Thanks for making me a little bit smarter today!
May 6th, 2011 at 4:27 am
I’m in 8th grade… how the heck am i supposed to understand this stuff. i’m just trying to figure out why magnets don’t affect flash drives for a science experiment.
May 6th, 2011 at 4:31 am
i know that hard drives are a series of platters that write and read data through the use of tiny electromagnets. Now what about the flash drives. is that like completely different. I mean i know that flash drives don’t have discs inside of them but does it use magnets in the process as well… doesn’t anybody know the answer
May 6th, 2011 at 4:51 am
These fancy contraptions weren’t around in my day. When we had to read or write data, we did it ourselves with two tools: Pencil and Paper!!
May 11th, 2011 at 5:25 pm
Dude,
. For more information you may want to check out my comparison between flash and hard drives.
flash storage works via electrons and is non-magnetic. And normal magnets cannot harm it like erasing all the data (as in the good ole days of floppy disks
July 29th, 2011 at 5:08 am
Very interesting post. I will surely come back and read more of your posts. It is quite easy to read and understand at the same time very educational. Thank you.
Flash drives really makes a lot of difference in IT life today. It makes it easier to store and transfer data at a flash
October 3rd, 2011 at 9:10 pm
Flash refers (according to the inventor) the flash like a camera flash when it is erased