Random Access Memory or RAM is the up gradable type of computer memory that can be accessed easily. It is named as Random access memory because any byte can be accessed without touching the preceding byte. SAM or Serial Access Memory is the opposite type in which the memory is arranged in a series of memory cells that can accessed only in a sequential way. RAM is an essential part of computer and Printers. RAM can be classified into DRAM and SRAM. DRAM or Dynamic Random Access Memory which needs to be refreshed thousands of times per second. SRAM or Static Random Access Memory is faster than DRAM so that refreshing in not necessary. More over the SRAM gives the access time as low as 10 nano seconds compared to the 60 nano seconds of DRAM. But due to the high cost of SRAM, DRAM is commonly used in computers. RAM has volatile memory which will wipe off when the power is switched off. Virtual memory is the method of extending the RAM capacity with a part of the Hard drive and Shadow RAM is another kind of RAM in which the contents of the ROM is copied to read-write memory to reduce the access time. RAM disk is the partitioned region of the physical RAM that can act as a faster Hard disk.