In this article, we look at the memory card, providing a guide to what it is for, and how it works


A CompactFlash card (left) and Secure Digital (SD) card from Lexar’s Professional UHS-I range

A memory card is the digital equivalent of film – a place to which your photographs are recorded. However, the earliest digital cameras didn’t use memory cards. Instead, the camera had a portion of non-volatile memory (it remembers even with the power switched off) built permanently into the camera. Eventually, proprietary replaceable memory cards were devised and, subsequently, standardised designs appeared.

For a long time, the most widely used memory card was the CompactFlash card, with the ‘Flash’ bit referring to the use of a specific type of non-volatile ‘flash memory’. A memory card is usually made from NAND flash memory, which works like an erasable electronically programmable read-only memory (EEPROM), but while EEPROMs had to be completely wiped clean before accepting new data, flash memory can erase and reprogram small blocks of memory at a time.

By today’s standards, CompactFlash cards are far from compact, but were marvelled at when they first arrived on the scene in 1994. There were even versions, made by IBM, that masqueraded as ‘memory’ cards, but were in fact miniature hard disk drives, or Microdrives. Back in 1999, a typical memory card would have space for 8MB or 16MB of data.

When Panasonic, Toshiba and SanDisk announced the Secure Digital (SD) card around the same time, they forecast not only a need but also the technical feasibility of squeezing 2,000MB of data into a card that would be a fraction of the size of a CompactFlash card. This was realised within a predicted five years and these days 128GB (128,000MB) and even 256GB-capacity cards are coming onto the market.

Memory cards are now cheaper and faster than ever, too. Just imagine what photography would be like without one.