If you have recently purchased a new cellphone, MP3 player or laptop computer, you may notice that it's compatible with Secure Digital cards. Some devices, such as laptops, have slots for inserting these cards, while MP3 players or cellphones may already come with an SD card installed.
SD cards are a type of memory card that inserts into a portable device such as a digital camera, MP3 player, laptop or cellphone. This removable media stores data ranging from audio and video files to applications and images. You can insert and remove an SD card from your device without deleting any data and typically, as is the case of digital cameras, review the files on the card directly from the device. You can use an SD card to temporarily transfer data between computers if the computers have an internal card reader or if you have an external memory card reader.
One of the significant benefits of using an SD card is the ability to save more files, such as pictures, than the device's internal hard drive allows. You can still save files at higher quality, thus a larger file size, and don't have to worry about degrading your songs, videos or images to prevent filling the hard drive. When you do fill your SD card, you can simply insert a blank card and can save the full card for future reference.
SD cards are available in several capacities. Original SD cards are officially available up to 2GB in capacity, although some manufacturers sell 4GB versions, while high-capacity SD cards can hold between 4GB and 32GB of information. Extended-capacity cards have the highest capacity yet, with a range of 32GB to 2TB. To put capacity in perspective, you can save up 673 photos to a 2GB memory card if you save each image as a 5-megapixel JPEG, with an approximate picture size of 2MB each. However, you will fit fewer images on your card if you use higher-quality image types, such as RAW, or if you're saving audio or video files.
Aside from the different capacity types, SD cards are available in a multitude of physical formats. Over time, SD cards have become increasingly smaller to accommodate smaller devices, including cellphones. The miniSD card is almost square in appearance, with a height of 21.55 mm by 20 mm in width. MicroSD cards are the smallest cards to date and, as of April 2011, many cellphones are compatible with this format. MicroSDs measure just 11 mm by 15 mm and are nearly two thirds of the size of the original SD card, which was 32 mm by 24 mm. However, if you have a device that's compatible with one type of SD card, you may be able to purchase an adapter so that you can use an SD card with a different physical form factor.