The Definition of an SD Card

What Is an SD Card?

Secure digital or SD cards are small 24 x 32 mm cards that hold rows of memory chips within pins. They plug into compatible SD slots on consumer electronics devices and hold "flash" memory that is retained even when the device is turned off. SD cards can hold additional memory ranging from 64 to 128 gigabytes, but your device may be limited to working with 32GB or 64GB cards.  

SD cards for GPS devices often come pre-loaded with supplemental maps or charts to greatly enhance map detail and supplemental travel information.

SD cards can also be used for media storage and are often used with smartphones

How SD Cards Work 

SD cards require a dedicated port on your electronics device. More and more computers are being manufactured with these slots, but you can connect a reader if you have an older device that didn't come equipped with one. The card’s pins match with and connect to this port. When you insert the card, your device effectively begin communicating with it through the card’s microcontroller. Your electronic device will automatically scan your SD card and import data from it. 


SD cards are remarkably tough. A card is not likely to break apart or even suffer internal damage if you drop it because it’s a solid piece with no moving parts. In fact, Samsung claims that its micro SD card can endure the crushing weight of 1.6 metric tons without suffering damage and that even an MRI scanner won’t delete the card’s data.

SD cards are said to be impervious to water damage as well. 

"Micro" SD Cards

A "micro" SD card performs the same functions as a full-size card, but it's much smaller – 15 x 11 mm. It's designed for smaller handheld GPS devices, smartphones and MP3 players. Digital cameras and recorders and game systems usually require full-size SD cards.