A CompactFlash card uses flash memory, also referred to as solid-state memory, along with a controller chip to write and read data by applying tiny electrical charges to the electrons in the cells of the memory chips. Flash memory generally stores information in individual blocks, and a user rewrites these blocks by erasing all the data and replacing it rather than changing it byte by byte as traditional memory does.
CompactFlash cards are a specific type of flash memory developed by SanDisk and initially marketed in 1994. They offer anywhere from 100 GB all the way down to 8 MB of storage and require dedicated card readers or adapters. Many portable media devices such as digital cameras incorporate the use of these flash cards.
There are two types of CompactFlash cards: Type I and Type II. The only significant difference between the two is thickness; Type I cards are 3.3 millimeters thick, while Type II cards have a thickness of 5 millimeters.
Since the development of the original CompactFlash card, solid state memory has become much more widespread as it became more cost-effective to put large amounts of storage space in solid-state drives. Modern laptops often use flash drives as replacements for traditional hard drives because they boot up faster and are less prone to breaking.