A card reader is a device, typically having a USB interface, for accessing the data on a memory card such as a CompactFlash, secure digital or Multimedia Card. Most card readers also offer write capability, together with the card, can function as a pen drive. Flash Memory Card Readers and Writers are used to easily transfer files such as digital pictures, mp3s, data files, and PDA files between computer and Memory Cards
The fastest way to get your digicam's images from a flash memory card is to use one of the readily available card readers. These come in many varieties depending on the desired computer interface. The most common type are made for PCs and connect to the USB port which can be categorized by the type and quantity of card slots: Single card reader (e.g. 1x SD-only), Multi card reader (e.g. 9-in-1) and Series card reader (e.g. 4x SD only).
Most readers can read the following types of Memory cards;
1. CompactFlash® Type I
2. CompactFlash® Type II
3. SD™ Card
4. miniSD™
5. MultiMediaCard™
6. RS-MMC™
7. Memory Stick™
8. Memory Stick PRO™
9 Memory Stick Duo™
10. Memory Stick PRO Duo™
11. SmartMedia™
12. xD™