SSC CGL 1 Sep 2016 Paper

The write-back method involves updating only the cache location and to mark it as updated with an associated flag bit, often called the dirty or modified bit. The main memory location of the word is updated later, when the block containing this marked word is to be removed from the cache to make room for a new block. The reason for the write back method is that during the time a word resides in the cache, it may be updated several times.