Compact Flash or CF as it is also known is a popular type of flash based memory. It was developed and released by SanDisk in 1994. This small device was.
Compact Flash solid state memory device which retains data even without power being applied to it. "Compact Flash" or CF defines the physical format (and electrical interface) of the card. Within the card are one or more solid state memory chips, plus a memory controller. CF cards actually come in two different sizes:

As you can see, the only physical difference is in the thickness of the card. All Canon EOS DSLRs can take both type I and type II cards, but some cameras can only accept type I cards. The thicker cards were originally either high capacity cards or microdrives. Today even high capacity cards are usually type I, but most microdrives are type II.
Types of Compact Flash Memory
Compact Flash memory cards fall into two categories. Type 1 card and Type II card The Compact flash also has 3 speeds CF, CF High Speed (using CF+/CF2.0), and an even faster CF3.0. The type I interface can supply up to 70mA to the card, the type II interface can supply up to 500mA, so you can see that a type II interface is required if the card draws a lot of power.
At 43mm (1.7") x 36mm (1.4") x 3.3mm (0.13"), the CF Type I card's thickness is about one-half of a current PCMCIA Type II card. It is actually one-fourth the volume of a PCMCIA card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs. It can be easily slipped into a passive 68-pin PCMCIA Type II to CF Type I adapter that fully meets PCMCIA electrical and mechanical interface specifications.
At 43mm (1.7") x 36mm (1.4") x 5mm (0.19"), the CF Type II card's thickness is equal to a current PCMCIA Type II card. It is actually less than one-half the volume of a PCMCIA card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs. It can be easily slipped into a passive 68-pin PCMCIA Type II to CF Type II adapter that fully meets PCMCIA electrical and mechanical interface specifications.
The only difference between CF Type I and CF Type II cards is the card thickness. CF Type I is 3.3 mm thick and CF Type II cards are 5mm thick. A CF Type I card will operate in a CF Type I or CF Type II slot. A CF Type II card will only fit in a CF Type II slot. The electrical interfaces are identical. CompactFlash is available in both CF Type I and CF Type II cards, though predominantly in CF Type I cards. The Microdrive is a CF Type II card. Most CF I/O cards are CF Type I, but there are some CF Type II I/O cards.

Use of Compact Flash Memory

The market demand for CF cards has surged with the advent of new computers, cameras and electronics products. CF technology has widespread application in digital cameras. The current roster of CFA members already includes several major companies that produce digital cameras. The momentum created by such companies as Canon, Epson, JVC, Kyocera, Kodak, Konica-Minolta, Pentax, Pretec, Ricoh, Nikon, Sanyo and Yashica joining a single organization committed to the development of CF-based products, has propelled the adoption of the CF specification as an industry standard.
CompactFlash and CF cards are the film in small, lightweight digital cameras currently being sold and developed for the mass consumer market. "Canon's commitment to the CFA is driven by our belief that CompactFlash cards has become the film for next-generation digital cameras," said Toru Takahashi, Director and Group Executive of Research and Development at Canon, Inc.
With CF cards, camera users can easily eject their "film" and transport the images via the PCMCIA Type II adapter card or a CF reader to either obtain prints or move the photos to another digital system such as a computer, Pocket PC, etc. One 64MB CF card, which can be used repeatedly for more than 100 years to take millions of pictures, will store 100 or more digitally compressed images or photos. Higher capacity CompactFlash cards (currently up to 12GB) and Microdrives up to 4GB can store large numbers of images even with today's highest resolution digital cameras. Photos can be "developed" in seconds and transmitted or printed using high-resolution color printers. Copy shops, camera stores, desktop-publishing service bureaus, and major retail stores already have digital photo printing services that can accept CF cards and print 4x6 photos for as little as 17 cents.
Digital camera owners can use CF cards in a variety of ways. Real estate agents can take pictures of new homes that just came on the market and send them via modem or E-mail to prospective, out-of-town buyers who can view the pictures on their computers. Insurance agents can take pictures of accident scenes, incorporate these pictures into accident reports they compose on their computers and later submit for processing and payment. People can take pictures of family celebrations and later that day send the photos electronically to relatives or friends in distant states or countries. Camera users no longer need to "waste" the shots at the end of a roll of 35mm film just to get pictures developed. They can use as much or as little of the CF card as they need and then erase the CF when they have prints in hand or have stored the images digitally in their PC. The CF is then free for more photo taking. With CF film, taking pictures is less expensive because consumers don't have to keep buying new rolls of film. And "developing" photos in the traditional sense is eliminated altogether.
In general, when using CompactFlash cards, deleted files can be recovered. Also, files on cards that have been re-formatted or the card's file system has been corrupted may be recovered. There are a number of applications to recover files.
After the deletion of files, writing new files or re-formatting the CompactFlash cards may cause some of the old files to be unrecoverable.
What this means to CompactFlash card users:
1) Photo files as well as other types of files that have been deleted accidentally may be recovered from CompactFlash cards.
2) Confidential information contained in deleted files or on formatted CompactFlash cards may be recovered from CompactFlash cards that are given or sold to other persons.

CompactFlash® is a very small removable mass storage device. First introduced in 1994 by SanDisk Corporation, CF™ cards weigh a half ounce and are the size of a matchbook. They provide complete PCMCIA-ATA functionality and compatibility plus TrueIDE functionality compatible with ATA/ATAPI-4. At 43mm (1.7") x 36mm (1.4") x 3.3mm (0.13"), the device's thickness is less than one-half of a current PCMCIA Type II card. It is actually one-fourth the volume of a PCMCIA card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to PCMCIA ATA specs. It can be easily slipped into a passive 68-pin Type II adapter card that fully meets PCMCIA electrical and mechanical interface specifications.
CompactFlash cards are designed with flash technology, a non-volatile storage solution that does not require a battery to retain data indefinitely. CompactFlash storage products are solid state, meaning they contain no moving parts, and provide users with much greater protection of their data than conventional magnetic disk drives. They are five to ten times more rugged and reliable than disk drives including those found in PC Card Type III products. CF cards consume only five percent of the power required by small disk drives.
CF cards are also available for data storage using the Microdrive. CF I/O cards are available as modems, Ethernet, serial, digital phone cards, laser scanners, BlueTooth wireless, 802.11b WiFi LAN, etc.
Dual 3.3V & 5V Operation – CF and CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages
Connector – The connector used with CompactFlash is similar to the PCMCIA Card connector, but with 50 pins. Years of field experience in portable devices have proven the reliability and durability of this connector in applications where frequent insertions and ejections of the card are required. Other small form factor flash cards use connector technology that is not reliable or durable in these applications .
Shock – CF cards have an operating shock rating of 2,000 Gs, which is equivalent to a 10-foot drop. With typical usage, a CF card can be used for more than 100 years with no loss or deterioration of data.
Power – Typically consuming less than five percent of the power than that required to operate 1.8" and 2.5" disk drives, CF cards run at 3.3V or 5V with a single power supply. This makes them ideal for a range of current and next-generation, small-form factor consumer applications.
Operating System Support – Numerous platforms and operation systems support the PCMCIA-ATA standard, including Windows®, Windows XP, OS/2, Apple System 7, most types of UNIX, and many others. These all also support CompactFlash, CF disk drives and CF I/O cards..
Data Reliability – CompactFlash data is protected by built-in dynamic defect management and error correction technologies.
Cost – CompactFlash provides the lowest cost flash storage solution for all capacities. With the built-in controller, a wide variety of low cost flash technologies can be used. The built-in controller lowers costs further by reducing costs in the host device and allowing defective flash chip cells to be mapped out, thus increasing flash chip yields.
CompactFlash® is a small, removable mass storage device. First introduced in 1994, CompactFlash cards weigh a half ounce and are the size of a matchbook. They provide complete PCMCIA-ATA functionality and compatibility.
CompactFlash cards are designed with flash technology, a nonvolatile storage solution that does not require a battery to retain data indefinitely.
The CompactFlash card specification version 3.0 supports data rates up to 66MB/sec and capacities up to 137GB.
CompactFlash storage products are solid state, meaning they contain no moving parts, and provide users with much greater protection of their data than conventional magnetic disk drives. They are five to ten times more rugged and reliable than disk drives including those found in PC Card Type III products. CF cards consume only five percent of the power required by small disk drives.
CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages.
CF+ data storage cards are also available using magnetic disk (Microdrive).
CF+ I/O cards include modems, Ethernet, 802.11b WiFi, serial, Bluetooth wireless, digital phone cards, USB, laser scanners, VGA, etc.
The connector used with CF and CompactFlash is similar to the PCMCIA Card connector, but with 50 pins. Years of field experience in portable devices have proven the reliability and durability of this connector in applications where frequent insertions and ejections of the card are required. Other small form factor flash cards use connector technology that is not reliable or durable in these applications .
CompactFlash provides the lowest cost flash storage solution. With the built-in controller, a wide variety of low cost flash technologies can be used. The built-in controller lowers costs further by reducing costs in the host device and allowing defective flash chip cells to be mapped out, thus increasing flash chip yields. CompactFlash provides the lowest cost data storage solution.
When compatibility, interoperability, reliability, cost, and performance count, CF and CompactFlash cards are the ATA-compatible solution that delivers
Many leading consumer electronics companies, including the CFA's roster of members, have designed CF technology into next-generation products developed for consumer markets. CF technology is widely used in such products as portable and desktop computers, digital cameras, handheld data collection scanners, PDAs, Pocket PCs, handy terminals, personal communicators, advanced two-way pagers, audio recorders, monitoring devices and set-top boxes. CF technology offers all of these applications new and expanded functionality while enabling smaller and lighter designs

The market demand for CF cards has surged with the advent of new computers, cameras and electronics products. CF technology has widespread application in digital cameras. The current roster of CFA members already includes several major companies that produce digital cameras. The momentum created by such companies as Canon, Epson, JVC, Kyocera, Kodak, Konica-Minolta, Pentax, Pretec, Ricoh, Nikon, Sanyo and Yashica joining a single organization committed to the development of CF-based products, has propelled the adoption of the CF specification as an industry standard.
CompactFlash and CF cards are the film in small, lightweight digital cameras currently being sold and developed for the mass consumer market. "Canon's commitment to the CFA is driven by our belief that CompactFlash cards has become the film for next-generation digital cameras," said Toru Takahashi, Director and Group Executive of Research and Development at Canon, Inc.
With CF cards, camera users can easily eject their "film" and transport the images via the PCMCIA Type II adapter card or a CF reader to either obtain prints or move the photos to another digital system such as a computer, Pocket PC, etc. One 64MB CF card, which can be used repeatedly for more than 100 years to take millions of pictures, will store 100 or more digitally compressed images or photos. Higher capacity CompactFlash cards (currently up to 12GB) and Microdrives up to 4GB can store large numbers of images even with today's highest resolution digital cameras. Photos can be "developed" in seconds and transmitted or printed using high-resolution color printers. Copy shops, camera stores, desktop-publishing service bureaus, and major retail stores already have digital photo printing services that can accept CF cards and print 4x6 photos for as little as 17 cents.
Digital camera owners can use CF cards in a variety of ways. Real estate agents can take pictures of new homes that just came on the market and send them via modem or E-mail to prospective, out-of-town buyers who can view the pictures on their computers. Insurance agents can take pictures of accident scenes, incorporate these pictures into accident reports they compose on their computers and later submit for processing and payment. People can take pictures of family celebrations and later that day send the photos electronically to relatives or friends in distant states or countries. Camera users no longer need to "waste" the shots at the end of a roll of 35mm film just to get pictures developed. They can use as much or as little of the CF card as they need and then erase the CF when they have prints in hand or have stored the images digitally in their PC. The CF is then free for more photo taking. With CF film, taking pictures is less expensive because consumers don't have to keep buying new rolls of film. And "developing" photos in the traditional sense is eliminated altogether.
Small, handheld audio recorders employ CF technology. Audio messages are be stored on CF cards capable of holding over 60 minutes of sound. With CF slots designed across numerous platforms, the digital messages can be moved to several different kinds of products using adapter cards. An office supervisor on their way to work could dictate a message to a subordinate who had submitted a budget update on a spreadsheet. The supervisor could record comments to the subordinate indicating specific areas on the spreadsheet where data seemed inconsistent. Later, at the office, the spreadsheet user would insert the CF card into a PC and would work on the document while being guided by the supervisor's pre-recorded voice comments linked to the spreadsheet file.

Audio (MP3) Players?

Small, MP3 players employ CF technology. MP3 music files are stored on CF cards capable of holding hours of near CD quality sound. With CF slots designed across numerous platforms, the MP3 files can be moved from a PC to a CF card and played in a CF MP3 Player. Small size and totally skip proof operation make a CF MP3 player a cool accessory..

Capacities?

CF cards are available in capacities from 16MB to 12GB. The CF Specification can support capacities up to 137GB.
While many CF applications can operate with low capacity CF cards, higher capacity cards are increasingly used as digital camera resolution rises.

Dual Voltage Support?

CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages

The Connector?

The connector used with CompactFlash is similar to the PCMCIA Card connector, but with 50 pins. Years of field experience in portable devices have proven the reliability and durability of this connector in applications where frequent insertions/ejections of the card are required. Other small form factor flash cards use connector technology that is not reliable or durable.

Cost?

CompactFlash provides the lowest cost flash storage solution. With the built-in controller, a wide variety of low cost flash technologies can be used. The built-in controller lowers costs further by allowing defective cells to be mapped out, thus increasing flash chip yields and by reducing costs in the host device.
Compact Flash Specifications

 

Advantages

Disadvantages