Limitations of Flash memory

Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards, and USB flash drives for general storage and transfer of data between computers and other digital products.

One limitation of flash memory is that although it can be read or programmed a byte or a word at a time in a random access fashion, it must be erased a "block" at a time. This generally sets all bits in the block to 1. Starting with a freshly erased block, any location within that block can be programmed. However, once a bit has been set to 0, only by erasing the entire block can it be changed back to 1. In other words, flash memory (specifically NOR flash) offers random-access read and programming operations, but cannot offer arbitrary random-access rewrite or erase operations. A location can, however, be rewritten as long as the new value's 0 bits are a superset of the over-written value's. For example, a nibble value may be erased to 1111, then written as 1110. Successive writes to that nibble can change it to 1010, then 0010, and finally 0000. Although data structures in flash memory cannot be updated in completely general ways, this allows members to be "removed" by marking them as invalid. This technique must be modified somewhat for multi-level devices, where one memory cell holds more than one bit.

Another limitation is that flash memory has a finite number of erase-write cycles (most commercially available flash products are guaranteed to withstand 100,000 write-erase-cycles for block 0, and no guarantees for other blocks. This effect is partially offset by some chip firmware or file system drivers by counting the writes and dynamically re-mapping the blocks in order to spread the write operations between the sectors; this technique is called wear leveling. Another mechanism is to perform write verification and re-mapping to spare sectors in case of write failure, which is named bad block management (BBM). With these mechanisms in place, some industry analysts have calculated that flash memory can be written to at full speed continuously for 51 years before exceeding its write endurance, even if such writes frequently cause the entire memory to be overwritten. This figure (51 years) involved a worst-case scenario using specific data parameters and should not be confused with a particular "shelf life" for a flash memory device. The bottom line is that a typical user using a commercial device, such as a camera, with a flash drive will probably not wear out the memory for the effective life of the camera. However, it - like any other hardware component - can fail. Anyone using flash memory (and any other medium) for critical data would be well advised to backup the data to another device (preferably of a different medium). Many have found it very fast and reliable for 'read-only' operating systems such as thin clients and routers.

Advantages of professional digital cameras

Advantages of Professional digital cameras are as follows:

• Immediate image review and deletion is possible; lighting and composition can be assessed immediately, which ultimately conserves storage space.
• The ability to shoot in raw image format (images that contain tagged data directly from the sensor). However, as of this writing, there are a number of proprietary RAW formats, some of which require specific software to manipulate.
• Faster workflow: Management (color and file), manipulation and printing tools are more versatile than conventional film
• Immediate image review and deletion is possible; lighting and composition can be assessed immediately, which ultimately conserves storage space.
• The ability to shoot in raw image format (images that contain tagged data directly from the sensor). However, as of this writing, there are a number of proprietary RAW formats, some of which require specific software to manipulate.
• Faster workflow: Management (color and file), manipulation and printing tools are more versatile than conventional film processes. However, batch processing of RAW files can be time consuming, even on a fast computer.
• Digital manipulation: A digital image can be modified and manipulated much easier and faster than with traditional negative and print methods.
• Digital manipulation: A digital image can be modified and manipulated much easier and faster than with traditional negative and print methods.

Consumer’s sales promotions in US

In the U.S, consumer sales promotion sponsors are very careful to disassociate themselves from any suggestion that players must pay to enter, as this would bring them into conflict with federal lottery laws. Sweepstakes typically involve enticements to enter a consumer promotion for prizes that range from fantastic wins such as cars or large sums of money to smaller prizes that are "hot" such Apple iPods. There should be no cost to the entrant to enter for the sweepstakes prize and sweepstakes winners should also not be required to pay a fee of any type to receive their prizes. Because of their potential for abuse, sweepstakes are heavily regulated in many countries. The U.S., Canada, and individual U.S. state all have laws covering sweepstakes, resulting in special rules depending on where the entrant lives. The U.S. Federal Trade Commission exercises some authority over sweepstakes promotion and sweepstakes scams in the United States.

Most corporate-sponsored sweepstakes promoted in the United States limit entry to U.S. citizens, although some allow entry by legal residents of both the United States and Canada. Among the most commonly known sweepstakes in the United States are the American Family Publishers Sweepstakes, Publisher's Clearing House and Reader's Digest Sweepstakes, each of which strongly persuade entrants to purchase magazine subscriptions by placing stickers on contest entry cardstock while promising multi-million dollar (annuity) winners who will be "announced on TV." The American Family Publishers sweepstakes traditionally used paid advertisements during NBC's The Tonight Show to announce its grand prizewinners. Fast-food restaurants frequently use sweepstakes to boost business. One of the most popular has been the McDonald's Monopoly promotion. Soft drink companies also sponsor many sweepstakes, such as the Pepsi Billion Dollar Sweepstakes game and the Pepsi Stuff loyalty rewards program that allowed Pepsi drinkers to accumulate points from packages and cups and redeem them for high-quality, free merchandise. Pepsi Stuff was Pepsi's largest and most successful long-term promotion ever and it ran for many years in the US and in many countries around the world. Other sponsors may require the submission of a UPC of a company product for entry into the sweepstakes drawing. In most sweepstakes, entrants and their relatives must not be related to the sponsor or promoter.