NOR flash that was developed by Intel in 1988 with unique feature of long erase and write times and its endurance of erase cycles ranges from 10,000 to 100,000 makes it suitable for storage of program code that needs to be infrequently updated, like in digital camera and PDAs. Though, later cards demand moved towards the cheaper NAND flash; NOR-based flash is hitherto the source of all the removable media. Followed in 1989 Samsung and Toshiba form NAND flash with higher density, lower cost per bit then NOR Flash with faster erase and write times, but it only allows sequence data access, not random like NOR Flash, which makes NAND Flash suitable for mass storage device such as memory cards.

SmartMedia was first NAND-based removable media and numerous others are behind like MMC, Secure Digital, xD-Picture Cards and Memory Stick. Flash memory is frequently used to hold control code such as the basic input/output system (BIOS) in a computer. When BIOS needs to be changed (rewritten), the flash memory can be written to in block rather than byte sizes, making it simple to update. On the other hand, flash memory is not practical to random access memory (RAM) as RAM needs to be addressable at the byte (not the block) level. Thus, it is used more as a hard drive than as a RAM.

Because of this particular uniqueness, it is utilized with specifically-designed file systems which extend writes over the media and deal with the long erase times of NOR flash blocks. JFFS was the first file systems, outdated by JFFS2. Then YAFFS was released in 2003, dealing specifically with NAND flash, and JFFS2 was updated to support NAND flash too. Still, in practice most follows old FAT file system for compatibility purposes.

Although it can be read or write a byte at a time in a random access fashion, limitation of flash memory is, it must be erased a "block" at a time. Starting with a freshly erased block, any byte within that block can be programmed. However, once a byte has been programmed, it cannot be changed again until the entire block is erased. In other words, flash memory (specifically NOR flash) offers random-access read and programming operations, but cannot offer random-access rewrite or erase operations.