Storage Cards You have some important programs such as digital photos, Adobe Acrobat files and e-books . But where will it all fit? Throw them all on an add-on storage card, available at many retailers in stores and online. All modern PDAs accept some form of storage card which allows you add more memory for programs and data on our PDA. CompactFlash (CF) cards are the cheapest since they've been around since 1994 and both digital cameras and PDAs use them. CompactFlash cards are designed with flash technology, a non-volatile storage solution that does not require a battery to retain data indefinitely. They are quite fast, transferring data on a 16 bit data bus. Pocket PCs, Handheld PCs and the HandEra Palm OS PDA have CF card slots. MMC cards (MultiMedia Card) are the size of a postage stamp and wafer thin. Casio was the first PDA manufacturer to include an MMC slot in their EM-500 Pocket PC. Some MP3 players also use this type of card. Their benefit is their incredibly small size. However, they generally aren't available in capacities above 64 megs and they are slow, having a 1 bit data bus.

SD cards (Secure Digital) are the same wafer-thin postage stamp size as MMC cards. However, they have a sliding lock on the side (like a floppy) to protect the data on them from being modified or erased when needed. They also have cryptographic copyright protection (useful for such things as books and music sold on SD cards). SD cards are faster than MMC cards since they have a 4 bit data bus and a max transfer rate of 2 MB(megs)/second. All Compaq/HP iPAQ models have a built-in SD card slot that accepts both MMC and SD cards. Memory Stick is Sony's own trademarked invention. They're fairly small long rectangular purple cards that range in capacity from 16 to 128 megs. For years they've sold MP3 players, digital cameras and notebook computers with a slot that accepts Memory Sticks.