xD-Picture Card

The xD-Picture Card is a type of flash memory card, used mainly in digital cameras. xD originally stood for extreme Digital.[1] The cards were developed by Olympus and Fujifilm and introduced into the market in July 2002. Toshiba Corporation and Samsung Electronics manufacture the cards for Olympus and Fujifilm. xD cards are now sold under other brands, including Kodak, SanDisk, and Lexar.
xD cards are used in Olympus and Fujifilm digital cameras and Olympus digital voice recorders; Fujifilm also made an MP3 player that used the cards. As of 2006, xD cards are available in capacities of 16 MB, 32 MB, 64 MB, 128 MB, 256 MB, 512 MB, 1 GB, and 2 GB. xD cards have dimensions of 20 mm × 25 mm × 1.78 mm, and each weighs 2.8 grams

SDHC

A new SD format, SDHC (Secure Digital High Capacity, SD 2.0), allows capacities in excess of 2 GB. SDHC uses the FAT32 file system which supports a higher data density than FAT16[10]. It uses the same form factor as SD, but the SD 2.0 standard in SDHC uses a different memory addressing method (sector addressing vs byte addressing), thus theoretically reaching a maximum capacity of up to 2048GB. SDHC cards only work in SDHC compatible devices, but standard SD cards work in both SD and SDHC devices. The SDHC trademark is licensed to ensure compatibility.[11]

In August 2007 Toshiba announced that they would be launching a 32GB SDHC card and an 8 GB microSDHC card worldwide in January 2008. Toshiba also announced a 16GB version available in the last quarter of 2007.

A number of Key Features have been published for each:

1.SDHC Memory Card (High Speed Type) (1) Realizes maximum write speed of 6 MB per sec. (2) "Class 4” SD Speed Class, guaranteeing sustained data write at 4 MB/s. (3) Integrates highly secure CPRM copyright technology.

2. microSDHC Memory Card (1) Realizes large 8 GB capacity in a microSDHC Card. It can store 139 hours of music at a bit rate of 128kbit/s. (2) "Class 4” SD Speed Class, guaranteeing sustained data write at 4 MB/s. (3) Integrates highly secure CPRM copyright technology.

SDHC cards have SD Speed Class Ratings defined by the SD Association. The SD Speed Class Ratings specify the following minimum sustained write speed on to empty SDHC cards:

Class 2: 2 MB/s
Class 4: 4 MB/s
Class 6: 6 MB/s

As of April 2007, examples of devices which support the SDHC format include:

Photo / video
- Recent models of Canon PowerShot (aka Digital IXUS and IXY Digital),
Canon EOS, Casio Exilim, and Panasonic Lumix digital cameras
- The Nikon D40, D40x and Nikon D80, Pentax K100D, Pentax K110D (with
ROM Firmware ver. 1.01 and later) and the Pentax K10D digital SLRs as
well as ROM updates for other Pentax models
- Panasonic HDC-SD1 and SD5 camcorders
- The Kodak Z1275 will support the SDHC cards up to 8 GB.
- The Sanyo Xacti HDTV video camera
- The Ricoh Caplio R5 (with Firmware v1.6 or later) and Caplio R6.
Audio
- Cowon D2
- Creative Labs ZEN
- Edirol R-09 Solid State Digital Audio Recorder (Firmware 1.10)
- Sansa e200 series with Rockbox firmware (all non -R models) [12]
- Zoom H2
Readers
- SanDisk MicroMate compact USB SD adapter
- Kingston MobileLite 9 Multi Reader
- SanDisk Sansa View
- YE Data YD-8V08 internal floppy disk drive + 18-in-one internal USB
memory card reader/writer
- One Laptop Per Child XO laptops
Other devices
- The HTC Touch and TyTN II smartphones
- The Palm Treo 680
- The Nokia N800 Tablet
- The HTC P3600
- Several Garmin GPS devices such as the Zumo and Nuvi with the proper
software version.
- Nokia N95 mobile phone

Secure Digital card

Secure Digital (SD) is a flash (non-volatile) memory card format developed by Matsushita, SanDisk and Toshiba for use in portable devices, including digital cameras, handheld computers, PDAs and GPS units. As of 2006, SD card capacities include 8MB, 16MB, 32MB, 64MB, 128MB, 256MB, and 512MB, 1GB, 2 GB, 4 GB, 6 GB, 8 GB (4-32 GB: SDHC)[1] and 32GB.

The format has proven to be very popular. However, compatibility issues between older devices and the newer 2 GB and larger cards and the SDHC format have caused considerable confusion for consumers.

Form factor
SD cards are based on the older MultiMediaCard (MMC) format, but have a number of differences:

- The SD card is asymmetrically shaped so that it cannot be inserted upside down, whereas an MMC will go in most of the way but not make contact if inverted.

- Most SD cards are physically thicker than MMCs. SD cards generally measure 32 mm × 24 mm × 2.1 mm, but can be as thin as 1.4 mm, just like MMCs (see below).
The contacts are recessed beneath the surface of the card (like Memory Stick cards), protecting the contacts from contact with the fingers

- SD cards typically have higher data transfer rates, but this is always changing, particularly in light of recent improvements to the MMC standard.

- Digital rights management features are available but are seldom used.

Devices with SD slots can use the thinner MMCs, but the standard SD cards will not fit into the thinner MMC slots. SD cards can be used in CompactFlash or PC card slots with an adapter. miniSD and microSD cards can be used directly in SD slots with a physical interface adapter. There are some SD cards with a USB connector for dual-purpose use, and there are card readers which allow SD cards to be accessed via many connectivity ports such as USB, FireWire, and the common parallel port. SD cards can also be accessed via a floppy disk drive with a FlashPath adapter.