Memory card (Flash memory)

Introduction to Flash memory

Flash memory is a kind of semiconductor-based, non-volatile, rewritable computer memory; that is, it has many of the same characteristics as RAM, except that the data is not wiped out when the machine is turned off. Flash memory stores bits of data in memory cells, but the data remains saved even when electrical power is cut.

Due to its higher speed, durability, and low energy consumption, flash memory is ideal for many applications, such as digital cameras, mobile phones, printers, PDAs, laptop computers, and device that can record and play back sound, such as mp3 players. What's more, this kind of memory has no moving parts, which makes it very shock-resistant.

Types of memory cards

There are many competing, incompatible memory card formats, almost one for every manufacturer. Among these formats of memory cards, the most common are


Dimensions (mm)Volume (mm3)Weight (g)# of connectorsTransfer rateTheoretical capacityTheoretical size
Compact Flash type I43 x 36 x 3,35 1083,35020 MB/s137 GB128 GB
Compact Flash type II43 x 36 x 57 74045020 MB/s137 GB12 GB
SmartMedia37 x 45 x 0,81 2652222 MB/s128 MB128 MB
MMC24 x 32 x 1,41 0751,3720 MB/s128 GB8 GB
MMC Plus24 x 32 x 1,41 0751,3752 MB/s128 GB4 GB
RS-MMC MMC Mobile24 x 16 x 1,45381,3138 MB/s128 GB2 GB
MMC Micro14 x 12 x 1,1185< 113128 GB2 GB
Memory Stick Standard, Pro21,5 x 50 x 2,83 0104102 MB/s128 MB128 MB
Memory Stick Duo, Pro Duo20 x 31 x 1,699221020 MB/s32 GB16 GB
Memory Stick Pro-HG20 x 31 x 1,699221060 MB/s32 GB32 GB
Memory Stick Micro M212,5 x 15 x 1,222521020 MB/s32 GB8 GB
SD24 x 32 x 2,11 6132920 MB/s32 GB32 GB
mini SD20 x 21,5 x 1,460211112 MB/s32 GB4 GB
micro SD15 x 11 x 11650,3810 MB/s32 GB12 GB
xD25 x 20 x 1,88902,8189 MB/s8 GB2 GB

Memory card readers

It should be noted that there are multi-format memory card readers, most of which can be plugged into a USB port.

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