Information is normally kept in some storage system viz. Main memory, and the processing of this information is done by CPU. Since the access time taken by CPU is much less as compared to that of Main memory thus in order to match with CPU speed information is copied from main memory into a faster storage system- CACHE memory.Cache is placed between CPU and Main memory because its access time is less than the access time of main memory by a factor of 5 to 10.Working- When we need a particular piece of information, we first check whether it is in cache or not.If it is, we use the information directly from the cache;If it is not, we use the information from source, putting a copy in cache under the assumption that we will need it soon.Mapping- For mapping between Cache memory and Main memory following three methods are employed-1) Associative Mapping- makes use of associative memory.2) Direct Mapping3) Set-associative mapping.dear Kkusumkshp,Mapping procedure between cache and memory is very lengthy to explain here so I would suggest you to refer to some standard book of Computer Architecture(eg. M.Morris Manno). You will get the better explaination there.