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A cold buffer is a segment of a computer memory reserved for temporary data storage that has not been accessed or used recently. A cold buffer could also refer to an area of the memory that has not been written recently. The concept of cold buffers is associated with the data structure used for memory management schemes like the least recently used (LRU) policy.
Modern operating systems often use efficient memory management schemes such as segmentation and paging. In paging, the process is divided into pages and memory is divided into frames. The pages are placed in frames as per the demands of the process. Segmentation follows a similar mechanism. Only a subset of the pages that are essential for the execution of a process need to be placed in main memory; the other pages are placed on secondary storage. However, the cost of accessing a page from secondary memory is too costly, which is why a buffer is maintained. The buffer uses an algorithm like the LRU page policy, where the buffer only stores pages that are frequently referenced by the application. This is because the inherent nature of the application dictates that certain parts are accessed more frequently than others.
The buffer stores the least-recently accessed page on the top side, while other pages are pushed down every time a new entry is made in the buffer. The top side of the buffer contains memory addresses that are accessed regularly, and is known as the hot buffer, whereas the bottom side of the buffer contains memory addresses that have not been accessed in a while, and therefore is known as the cold buffer.