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Memory Card

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What is Memory Card?

Alternatively referred to as a flash memory card, a Memory card is a type of storage media that is often used to store photos, videos, or other data in electronic devices. Devices that commonly use a memory card include digital cameras, digital camcorders, handheld computers, MP3 players, PDAs, cell phones, game consoles, and printers.

There are a handful of different types of memory cards on the market, each varying in size, compatibility, and storage capacity.

Memory cards are a popular storage medium for many of today's consumer electronics devices, including digital cameras, cellophanes, handheld devices and other small electronic devices. Flash memory is non-volatile that is the memory card will not lose its data when removed from the device, and the cards can also be erased or reformatted and reused.

For most consumers, when buying a memory card you have to consider price, capacity and compatibility. Some devices will support up to a specific size of memory card, and a specific type of memory card as well. It’s important to read the information that came with your device to ensure you purchase a memory card that will work in your device.

 

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History of Memory card:-

PC Cards were the first commercial memory card formats to come out, but are now mainly used in industrial applications and to connect I/O devices such as modems. Since 1994, a number of memory card formats smaller than the PC Card arrived; the first one was CompactFlash later Smart Media and Miniature Card. The desire for smaller cards for cell-phones, PDAs, and compact digital cameras drove a trend that left the previous generation of "compact" cards looking big. In digital cameras Smart Media and CompactFlash had been very successful. In 2001, SM alone captured 50% of the digital camera market and CF had captured the professional digital camera market. By 2005 however, SD/MMC had nearly taken over Smart Media's spot, though not to the same level and with stiff competition coming from Memory Stick variants, as well CompactFlash. In industrial and embedded fields, even the venerable PC card memory cards still manage to maintain a niche, while in mobile phones and PDAs, the memory card has become smaller.

Since 2010, new products of Sony and Olympus have been offered with an additional SD-Card slot. Effectively the format war has turned in SD-Card's favour.

 

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How Memory Card work?

Flash works using an entirely different kind of transistor that stays switched on (or switched off) even when the power is turned off. A normal transistor has three connections (wires that control it) called the source, drain, and gate. Think of a transistor as a pipe through which electricity can flow as though it's water. One end of the pipe (where the water flows in) is called the source—think of that as a tap or faucet. The other end of the pipe is called the drain—where the water drains out and flows away. In between the source and drain, blocking the pipe, there's a gate. When the gate is closed, the pipe is shut off, no electricity can flow and the transistor is off. In this state, the transistor stores a zero. When the gate is opened, electricity flows, the transistor is on, and it stores a one. But when the power is turned off, the transistor switches off too. When you switch the power back on, the transistor is still off, and since you can't know whether it was on or off before the power was removed, you can see why we say it "forgets" any information it stores.

A flash transistor is different because it has a second gate above the first one. When the gate opens, some electricity leaks up the first gate and stays there, in between the first gate and the second one, recording a number one. Even if the power is turned off, the electricity is still there between the two gates. That's how the transistor stores its information whether the power is on or off. The information can be erased by making the "trapped electricity" drain back down again.

 

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