The card reader is produced with a digital camera, but its use is no longer limited to digital cameras, but extends to more areas. The card reader, as the name implies, is a device that reads data, but it can not only support the reading of data, but also support the writing of data. Its initial design ideas are mainly to make up for the defects of digital camera data output. Because the early USB interface is not popular, so the output port of the digital camera is connected with the computer serial port, because the serial port data transmission speed is very low, if you copy this data to the hard disk, it will take a lot of waiting time, therefore, the card reader came into being. With the development of MP3, PDA and other digital products, a strong impetus to the development of card readers. MP3 standard 256M or 512M flash memory obviously can not meet our needs, so the acquisition of 1G or higher flash memory has become our standard configuration, but if we want to copy MP3 songs to flash memory, only through the MP3 player, and this time we need a dedicated connection, Drivers and software can be completed, so that the portable portability of the MP3 player is much worse, and if we use the card reader at this time, there is no need to MP3 player intervention at all, you can directly store the MP3 songs on the Flash memory, so that MP3 become more convenient to use.