Flash memory storage, also known as solid-state storage, is an electronic non-volatile storage medium that can be electrically erased and reprogrammed. Unlike optical and magnetic storage, flash memory devices have no moving parts but instead, data is stored as electrical charges on flash storage media.
Flash memory erases data in units called blocks. A block stored on a flash memory chip must be erased before data can be written. Flash memory retains data for an extended period of time, regardless of whether a flash-equipped device is powered on or off.
Flash memory was developed from EEPROM (electrically erasable programmable read-only memory) by Toshiba in the early 1980s and introduced to the market in 1984. Flash memory devices use two different logical technologies named after the NAND and NOR logic gates. The individual flash memory cells exhibit internal characteristics similar to those of the corresponding gates.
WHAT ARE THE DIFFERENCES OF THE NAND AND NOR ?
- While EPROMs had to be completely erased before being rewritten, NAND-type flash memory may be written and read in blocks (or pages) which are generally much smaller than the entire device. NOR-type flash allows a single byte to be written – to an erased location – or read independently.
- Whiles NAND flash reads and writes sequentially at high speed, NOR flash also provides high-speed random access. The NAND type operates primarily in memory cards, USB flash drives, solid-state drives, and similar products for general storage and transfer of data. NAND or NOR flash memory is also often used to store configuration data in numerous digital products.
Example applications of both types of flash memory include personal computers, PDAs, digital audio players, digital cameras, mobile phones, synthesizers, video games, scientific instrumentation, industrial robotics, and medical electronics.
Because they have no moving parts, flash memory systems are not subject to mechanical failures like hard disk drives or optical disc systems. They are therefore more resistant to shock and vibration. They consume less power, make no noise, are re-writable and have a longer expected life span than magnetic media.
Flash memory devices are very small in size and in addition to being non-volatile, offers fast read access times, although not as fast as static RAM or ROM. As with other solid-state technologies, flash memory is evolving with rapidly increasing capacity, ever-smaller physical sizes and continually falling prices.
Types of Flash Memory Media
The following types of flash memory media can be easily identified:
- Flash memory cards
- USB Flash drives
- Solid-state drives
Flash Memory Cards
One common type of flash memory media is the memory card. It is a small card containing one or more flash memory chips, a controller chip, other electrical components and metal contacts that connect the card to the device or reader with which it is being used.
Flash memory cards are very common with handheld computers, digital cameras, portable digital media players, smart phones, and other types of mobile devices. Desktop and notebook computers can also use them for data transfer to a computer from another device.
A flash memory card reader is built into most computers and many mobile devices and such readers can read and write to at least one type of flash memory media. The type of reader that one’s computer is built with, determines the type of flash memory card one can use. Flash memory media can be inserted into a flash memory reader only one way.
As such, many flash memory readers have the card type and direction sign imprinted next to each slot. Types of flash memory cards identified are:
- Compact Flash (CF) card
- Multi-Media Card (MMC)
- Memory Stick
- Secure Digital (SD) card
- XD Picture Card (XD)
The capacity of flash memory cards is always growing from 2GB, 4GB, and 8GB for standard cards, and 16GB to 32GB for high-capacity cards.
USB Flash Drive
A USB flash drive, also variously known as a thumb drive, pen drive, flash stick, jump drive, flash-drive, memory stick, or USB stick, consists of a flash memory media fixed into a self-contained unit that uses a USB (Universal Serial Bus) interface or connector. It is typically removable, re-writable and much smaller than an optical disc.
When connecting it to a computer or any device, it is plugged into a standard USB port. USB flash drives do not have batteries, so they become active only when plugged into a USB port. They are designed to be very portable and small enough to fit in a pocket. They are available in a wide range of sizes, colours, and appearances. USB flash drives are built into a variety of products such as wristbands, necklaces, sunglasses, pens, and many more.
Information can be read from or written to a USB flash drive shortly after connecting it to a USB port. When a flash drive is being used with a computer, it is assigned a drive letter by the computer. As of March 2016, flash drives with anywhere from 8 to 256 GB are frequently sold; less frequent are 512 GB and 1 TB units. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances.
Solid-state drives (SSDs) are special hard disk drives that use flash memory instead of spinning platters and magnetic technology. It is also sometimes called solid-state disk.
An SSD does functionally everything a hard drive does, but data is instead stored on interconnected flash memory chips that retain the data even when there’s no power present. These flash memory chips are of a different type than is used in USB flash drives, and are typically faster, and more reliable.
Solid-state drives are smaller and faster than usual hard disk drives. They use less power, are typically more resistant to physical shock, run silently, and have quicker access time. However, while the price of SSDs has continued to decline over time, SSDs are (as of 2018) still more expensive per unit of storage than HDDs and are expected to continue to be so into the next decade. In terms of storage capacity, it is more likely to find 500GB to 1TB units as primary drives in systems.
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