Memory Cards (SD, Secure Digital)
There are many types of memory cards available. The most popular currently is called SD, or Secure Digital cards. If you have a small digital camera, chances are it uses SD cards for picture storage.
Memory card sizing primer:
A single Terabyte is 1024 Gigabytes (TB)
A single Gigabyte is 1024 Megabytes (GB)
A single Megabyte is 1024 Kilobytes (MB)
A single Kilobyte is 1024 bytes (KB)
A single byte is 8 bits
A single bit is a single 1 or 0, which is the base method of storing data.
It’s important to know this before trying to understand what types of SD cards are available. The most common side of cards right now are sized in Gigabytes (4, 8, 16…).
Standard SD (Maximum 2 GB in size):
Many devices that were designed for the standard format in mind won’t work with the newer cards. If you find out your card can’t read anything over 2 GB, you need to stick to these older cards.
SDHC (Maximum 32 GB in size):
This format came when the need for more memory was evident. Now that 32 GB is being stressed by powerful cameras and video recorders, the need for more storage is happening again.
SDXC (Maximum 2 TB size):
This format, as of 2010, is still not widely available, but it should solve the storage need for quite some time.
Other Physical Sizes:
With the SD standard, there are more than just the standard size available. The most popular secondary format is called Micro SD. It is about 1/4th the size of a standard card, but is fully compatible with the large format if an adapter is used. These are most popular in cell phones where size and power usage count. Another format between the standard size and micro is called Mini SD, but it is not widely used.
Speed of SD cards:
All SD cards are not a like when it comes to speed. The cards are measured by two standards. First is the X rating, which is the same rating as CD-Rom drives (1x = 150 KB per second). An example of this would be a card measured at 150x read speed, which means it transfers files at a maximum of 22.5 MB per second. You have to be careful with buying a card based on the X rating because it could be the read or write speed. The second rating is the Class rating. An example of this would be “Class 6″, which means the card should be able to write data at 6 MB per second, so if you are buying a card for a video recorder or a high mega-pixel digital camera, it’s best to get a card with a high class rating.
Where are SD cards used?:
SD is the most popular format right now. It is used in things like cell phones, GPS devices, cameras, video recorders, media players, digital picture frames, and e-book readers.
Many desktop computers and most laptop computers have a SD card reader inside, so it makes using the cards even easier. You can also buy external memory card readers that connect to USB ports.
