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I just had a phone interview where I was asked this question. I am aware of ways to store in register or heap or stack, but cache specifically?
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Unlike other variables, volatile variables are written to and read from the main memory. The CPU does not cache the value of a volatile variable.
Cache memory is not to be confused with the broader term cache. Caches are temporary stores of data that can exist in both hardware and software. Cache memory refers to the specific hardware component that allows computers to create caches at various levels of the network.
Caching is a separate memory, yes, and it has it's own addresses, but when the CPU caches memory lines from RAM, it keeps a record of what RAM-addresses the memory was on, and keeps a map between RAM-address and cache-address. From the point of view of your program, the address is the same.
Not in C as a language. In GCC as a compiler - look for __builtin_prefetch.
You might be interested in reading What every programmer should know about memory.
Just to clear some confusion - caches are physically separate memories in hardware, but not in software abstraction of the machine. A word in a cache is always associated with address in main memory. This is different from the CPU registers, which are named/addressed separately from the RAM.
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In C, as in as defined by the C standard? No.
In C, as in some specific implementation on a specific platform? Maybe.
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