A block in computing is the smallest amount of data that can be transferred in an input / output operation between the main memory of a computer and peripheral devices or vice versa.
The size of the block or physical register will depend on the characteristics of the computer. In most cases, the size of the block is usually larger than that of the logical record. The adaptation consists of packing in each block as many logical records as possible. The packaging may be of a strong or weak type, depending on whether or not the leftover of a block is allowed, placing records between two contiguous blocks.
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