Memory units

Memory units

	Cache	Primary	Secondary
Nature	Volatile	Volatile	Non-Volatile
Power Off	Data will be lost	Data will be lost	Data never be lost
Speed	Fast	Fast	Slow
Storage	Temporary	Temporary	Permanent
Cost	Expensive	Expensive	Less Expensive
Refreshing	Not Required	Required	Not Required

	Cache Memory Cache memory is a very high speed semiconductor memory which can speed up CPU.  It acts as a buffer between the CPU and main memory. It is used to hold those parts of data and program which are most frequently used by CPU.
	RAM RAM(Random Access Memory) is the internal memory of the CPU for storing data, program and program result.   It is read/write memory which stores data until the machine is working.
	ROM ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. The information is stored permanently in such memories during manufacture.

Difference between RAM and ROM

	RAM		ROM
Types	Static	Dynamic	MROM	PROM	EPROM	EEPROM
Performance	Fast	Moderate	Slow
Refresh	Not Required	Required	Not Required
Uses	Cache	RAM	Storage Device
Size	Larger	Smaller	Larger
Power Consumption	More	Less	More
Storage	Temporary		Permanent
Cost	Expensive		Less Expensive
Program	Not possible		Not Possible	Possible
Erase	Not possible		Not possible		Possible
Time for erase	Not possible		Not possible		40 min	4to10milli seconds