Memory card

A memory card is a small electronic device that stores digital data. It uses flash memory technology, which can retain data without requiring continuous power. Therefore, when the device is powered off, the data remains intact.

Memory cards of this type are commonly used in digital cameras, modern smartphones, gaming devices, portable computers, and audio recording equipment. The card is inserted into a dedicated slot in the device, after which the device's operating system reads from or writes to the card.

How it works

Inside a memory card are one or more flash chips and a small controller. The controller manages how data is written, determines storage addresses, and handles error correction. Data is stored in cells that hold electrical charge; the level of charge is translated into binary numbers.

Common types

The most prevalent types on the market are SD (Secure Digital) and its smaller variants, microSD and miniSD. CompactFlash, commonly used in professional cameras, also exists, as do older formats such as Memory Stick and xMD. Storage capacity ranges from millions of bytes to hundreds of gigabytes or more.

Speed ratings and classes

Memory cards are labelled with ratings indicating their minimum write speed, which is important for video recording. Video applications requiring high quality need cards with sustained high speed; otherwise recording may stall.

Lifespan and data preservation

Flash cells have a limited number of write and erase cycles. With prolonged use, some cells can degrade, and the controller attempts to avoid using damaged sections. For this reason, it is recommended that important data be backed up elsewhere.