CompactFlash cards are thicker in size than SmartMedia cards since all the logistics are built into the card and therefore the camera does not need any extra facilities to read it. The card is based on “non-volatile” flash memory technology, which means it doesn't need current to hold information.
There are two types of CompactFlash cards on the market, The older Type I and the latest Type II. The latter is 5.5 mm thick, which is the same size as the common PMCIA Cards. Type I cards can be used in Type II slots, but not the other way around.
As CompactFlash cards do not contain any moving parts they are quite rugged and hardly susceptible to temperature variations. They will function normally in operating temperatures ranging from –25 to +75 degrees Celsius. CompactFlash cards have a lifespan of 100 years and no loss of memory will occur in normal use. They should be able to withstand drops from up to 3 meters. In addition to reliability and ruggedness, their solid state nature also means that they consume very little power.
Storage capacities for Type I range from 8 to 640 Mb, while Type II can hold an even more spacious 8GB. New technologies however, will see larger capacities in the near future.