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What is Secure Digital Card/meaning/concept

They are the best when it comes to storage in digital photo cameras and smartphones, we use all these cards, but what exactly do we have in our hands? Secure Digital Card

Secure Digital cards are the result of the evolution of MMC (MultiMediaCard) as a standardized format for storing and sharing information electronically. 

They are flat cards and rectangular in shape, but with one of the inclined angles, of which there are three measures: SD, miniSD and microSD, from the largest to the smallest, with the SD being the most popular (because it is the first and is still largely used cameras) and the microSD (for its extended use in the field of smartphones).

The three formats depend on the SD Card Association (SD Card Association), an entity that currently groups around 400 companies and was founded by the three companies that created this standard: Panasonic, Toshiba and SanDisk. Secure Digital Card

There are four different types of cards, according to characteristics such as the speed of access to the data provided

– The first of its kind is SDSC, which is the original format (in fact, its name stands for Secure Digital Standard Capacity) and which provides a bus speed of 12.5 MB/sec.

– The next evolution of these cards was the SDHC (Secure Digital High Capacity), which is version 2.0 of the standard announced in January 2006, which surpasses the limit of 2 GB per card, reaching up to 32 GB, even if the format be identical to the original SD in both physical and electrical terms, as compatible readers accept SDSC seamlessly, as in all later generations. They also double the speed, reaching 25 MB / s. Secure Digital Card

– SDXC (Secure Digital Extended Capacity) allows overcoming the 32 GB limitation present in SDHC cards, with a maximum limit of 2 Terabytes at a speed of 25 MB / s, identical to that offered by SDHC cards. This format was introduced in January 2009 and is defined in version 3 of the SD card standard, being the first to adopt the exFAT file format to replace FAT, something that will be discussed later. In this case, the speed increases again, oscillating between 50 and 104 MB / s. Version 4 of the standard allows this speed to be increased up to 312 MB/s thanks to the use of two communication lines . Secure Digital Card

– SDIO (Secure Digital Input / Output) cards allow you to connect a peripheral through an SD card slot. It is a format designed for use in PDAs, portable computers or devices with little expansion capacity, for the connection of peripherals such as cameras, communication receivers of any kind (GPS, TV) or network cards. On the one hand, the card is exactly like any SD data card , on the other hand, it has peripheral functionality that integrates it.

Typically, to ensure compatibility with all operating systems and devices, the file system adopted by these cards is exFAT, which is a variant of FAT for large storage devices as it overcomes traditional FAT targeting limitations .

When purchasing a memory card (whether any type of SD or others), you must take into account the speed at which they can read and write data, since normally their function is to serve as a storage medium for content recording applications multimedia, as in the case of photo / video cameras, or microSD of smartphones

In the case of the three types of SD cards, the speed is indicated by the “class” of the card, which is a number that tells us in MB / s (Megabytes per second) the minimum sequential recording speed . Secure Digital Card

Thus, a Class 2 card is guaranteed to write at least 2 MB/sec, while a Class 4 card is guaranteed to write at least 4 MB/sec.

Naturally, the higher the number, the better the performance that your SD card gives us in our devices, but a slot (slot in English) is also needed to enjoy its speed. Secure Digital Card

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