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Flash memory is a solid-state storage technology built on transistor-based charge traps, used in devices ranging from USB drives to NVMe SSDs. This content covers how flash evolved from early programmable read-only memory into the dominant long-term storage medium found in modern hardware.

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About this video

Flash memory is a solid-state storage technology rooted in the transistor, a component with no moving parts that operates as an electronic switch. By incorporating a charge trap into the transistor structure, engineers created memory cells capable of storing individual bits of data, and by packing billions of these cells onto chips, they built the storage devices in widespread use today — including USB flash drives, solid-state drives, mSATA modules, NVMe drives, and compact flash cards. Despite the fact that only some of these carry the word "flash" in their name, all rely on the same underlying technology, which now dominates the long-term storage market across consumer and enterprise hardware alike. The path to modern flash storage spans several decades of incremental advancement. Programmable read-only memory, introduced in 1956, allowed chips to be pre-loaded with data but could only be programmed once and had to be physically replaced to update. Erasable programmable read-only memory, developed in 1971, added the ability to wipe and reprogram a chip by exposing it to ultraviolet light through a small window, though this process erased all data at once and required removing the chip entirely. Electronically erasable programmable read-only memory, arriving in 1974, eliminated the need for UV light by using electrical signals to erase stored data, making it practical for firmware applications where equipment needed periodic updates without physical chip replacement. Flash memory distinguished itself from all prior technologies by enabling erasure at the block level rather than wiping the entire chip at once. Invented in 1980 and first sold commercially in 1987, early flash was large, expensive, and limited in capacity, making it impractical for many applications. Over time, advances such as multi-level cell technology and three-dimensional NAND architecture allowed manufacturers to shrink the physical footprint of storage chips while dramatically increasing their capacity and reducing cost per gigabyte. NAND flash, which follows the logic of a NAND gate, emerged as the primary variant used in storage products, while NOR flash — based on NOR gate logic — found more specialized applications. The result is a technology that has become the default choice for solid-state storage across the vast majority of modern computing devices.

What you'll learn

Aligned to

CompTIA Tech+
2.3 Explain the purpose of common internal computing components.
2.5 Compare and contrast storage types.
CompTIA A+ Core 1
3.3 Given a scenario, select and install storage devices.
CompTIA Server+
1.2 Given a scenario, deploy and manage storage.

Key terms

PROM
Programmable Read-Only Memory; an early chip that could be programmed once and could not be erased or reprogrammed.
EPROM
Erasable Programmable Read-Only Memory; a chip that stores data and can be erased by exposing it to UV light, then reprogrammed.
EEPROM
Electrically Erasable Programmable Read-Only Memory; a chip that can be erased and reprogrammed using electrical signals without UV light, enabling firmware updates.
NAND Flash
A type of non-volatile flash memory that stores data in blocks and erases data in blocks rather than the entire chip, making it the dominant technology in modern storage devices.
Solid State Drive
SSD
A storage device that uses flash memory chips with no moving mechanical parts to store data persistently, offering faster read/write speeds, lower latency, and greater durability than traditional hard disk drives. SSDs connect via SATA, NVMe, or M.2 interfaces.
Non-Volatile Memory Express
NVMe
A high-performance storage interface protocol designed for solid-state drives that connects directly to the CPU via the PCIe bus, delivering significantly lower latency and higher throughput than older SATA-based SSDs. NVMe is the standard interface for modern high-speed storage.
M.2
A small card-style internal drive form factor that plugs directly into a motherboard slot, supporting both SATA and NVMe interfaces to deliver high storage performance in a minimal physical footprint; standard in modern laptops and desktops.
CompactFlash
CF
A flash memory storage form factor used primarily in cameras and embedded systems, based on NAND or NOR flash technology.
USB Flash Drive
A portable storage device that uses NAND flash memory and connects via a USB interface for removable data storage.
NOR Flash
A type of flash memory that follows NOR gate logic, allowing random access to individual bytes; less common than NAND flash for mass storage.

Topics

Flash Memory Solid State Storage Nand Flash Eeprom Storage Form Factors Hardware

Transcript

This right here is a transistor. It is solid state, there are no moving parts on it, and it acts as a switch. We have also figured out how to put a charge trap inside of it to create a memory chip out of this, or memory cell, that will store a bit of information. We started cramming these all on chips in order to store data.

One of those technologies that we use commonly is this right here, a USB flash drive. This is a solid state drive that I have opened up so we can see the chips on the inside. This is an MSA drive, this is an NVMe drive, and this is compact flash. The reason why I am showing you all of this is because only two of them have flash in their name, but all of this is flash technology. In fact, flash has become so prevalent that most of the products that we buy nowadays that have long-term storage are using flash as its memory.

NAND And NOR

When it comes to flash there are two different types: there is the NAND type and there is the NOR type. The NAND follows a gate logic of a NAND gate, and the NOR follows the logic of a NOR gate. You do not necessarily need to know all the ins and outs of that. I wanted to point out the correlation between this and those gates, but really, primarily why I bring this up is because NAND is the primary technology that we use in our storage now, so you will see a lot of times this flash NAND.

How Solid State Storage Developed

We have developed solid state storage over time. In 1956 we created programmable read-only memory. This is before the charge trap was created, so essentially what we would do is engineer these chips that had some sort of programming on them that we could put into our machines, so that way we could use the program. So it was programmable read-only memory, and the only way that you could update it was that you would have to take that chip out, throw it away, and then put a new chip in. So that was the program side of this. Obviously not very dynamic, because the one chip was good for that program and only could be programmed once.

Then in 1971 we came out with erasable programmable read-only memory, or EPROM. What we would have is a chip that looked a lot like this, and it had the data that we could store on it. So it is programmable, but it also was erasable, and you would erase it by shining UV light into this little window right here, and then that would erase it. But you would be erasing the whole thing, which is not great. You would have to take it out, you would have to wipe it, and then you would have to reprogram it and then put it back in.

So in 1974 we came out with electronically erasable. You no longer needed UV light to erase it. Instead we could send an electrical signal to it to erase the whole chip. This is where a lot of firmware was started, right? Because we had these chips that we needed to have some sort of maybe coding for our different equipment, and they needed to be updated, and so we use things like EEPROM in order to be able to put that firmware on there and have it available for that equipment.

Even though the EEPROM, or electronically erasable PROM, gave us a step forward, there still was a problem, and that is that we would have to erase the whole chip any time we wanted to change the programming on it.

Where Flash Is Different

That is where flash is different. With flash we are able to store bits on it, but then we erase bits in blocks, and so now we do not have to erase the whole chip. We can erase parts of the chip. This was invented in 1980 and we start seeing it for sale in 1987.

When flash first came out, the physical sizes of the chip were much bigger and how much data could be stored on it was much smaller. It took up a lot of space and the cost of it was quite high, and so it was really impractical to use in a lot of scenarios. But over time we have developed technologies such as multi-level cells and V-NAND technology that have allowed us to shrink the size of this and increase the size of how much it can hold. So we have much bigger storage capacities now, making it the better choice in many situations to use over other technologies.

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