What is Ram, Rom and Cache & virtual Memory in Computer?

                           RAM ,ROM & CACHE

RAM(Random Access Memory):-

   Random access memory as same as main memory . Ram refers to a memory in which data and program can not only be obtained from primary storage , but also can be put into it. it is volatile, means the contents of the memory disappear once the current is turned off.
        Before a program runs,the program is loaded into a ram which allow the CPU direct access to the program.
example( if you have a smartphone and you have never open any application , you open any application as your choice if you open it,it take some second to view the content , after open you press home button and reopen a same application , this time you see a same application is open but it never take a same time becoz its already in ram so it is not take a long time , if you clear all apps from the task manager and stop application from the background and you open any application again so it takes some time again) 

Types of Ram in used in PC:-

Dynamic RAM is abbreviated as DRAM. DRAM being the more common type need to be refreshed (refreshing means recharging the chip with electricity) more often - thousand of times per second . Each time chip is refreshed , the content are lost. Recharging the chip quit often makes it slower then other RAMs.

Synchronous RAM:-

  This type of chip work faster than DRAM . This chip is faster because it moves at the speed of CPU's clock , it can moves data much more efficient than DRAM.

Static RAM:-

Static RAM need to be refreshed less often and hence contain data longer than DRAM ,ALL the RAM's are volatile but DRAM is slower and less expensive than SRAM , it is especially than DRAM. SRAM is used in super computer.

SIMM:-

SIMM

A SIMM, or Single  In line Memory Module, is a type of memory module used for random access memory in personal computer , it  differs from DIMM (the most predominant from of memory module today) in that the contacts on a SIMM are redundant on both sides of a modules.
memory modules evolved from need of saving motherboard space and ease memory expansion, instead 8 and 9 single DRAM DIP chips .only one additional memory module was needed to increase the memory of the computer. a few 80286- based computer used (often non-standard ) memory module like SIPP(Single In line Pin Package ).
SIPP's 30 pin often bent or broke during installation, which is why they are quick replaced by SIMMs which used content plates rather than pins.

DIMM:-

DIMM(Dual In line Memory Module ) Comprise a series of a random access memory integrated Circuit .These modules are mounted on a printed circuit board and designed for use in PC . DIMM's began to replace SIMM's the predominant module as Intel's Pentium process began to control the market.

The main deference SIMM and DIMM is that SIMM have 32 bits data path and DIMM have 62 bit data path.Since Intel's Pentium has (as do several other processor ) a 64 bit bus width , it required SIMM installed in matched pairs in order to use them.

CACHE MEMORY:-

Cache is a storage unit on the motherboard that allows you to store your frequently or most used information and avoids loading it from a slower storage medium. The main purpose of a cache is to cut down information access time for frequently used files.

In a simple term, cache memory is a special type of high speed memory built onto or next to the processor , your processor moves and works with lot of data . sometimes , your processor is work on a problem and needs to set it aside and start working an other before picking up the original problem , Without cache , your processor would have to store the set aside data into conventional memory (RAM) .while there is no particular reason your processor cannot do this. it's nowhere near as your processor.Designers figured out that there had to be a much faster and more efficient way for this happen.

Depending on what you do, the amount of cache your system has , can greatly increase or decrease the overall speed of system . for example a 405MHz Pentium III has lot more cache than a 405MHz celeron, even both chips has a same clock speed ,they do not perform same at the same level of situation,

Types of cache memory:

L1 Cache:

L1 Cache is also know as on board or primary cache and is built into the CPU itself. L1 cache is typically very small in size (for most of the computer is 16kb-128kb although this is changing rapidly) but it is very fast.

 L2 Cache:

L2 cache memory is also known as external or secondary cache , it is built into a separate chip, but it is still much faster then conventional memory because it , too is not subject to the speed limitation of the motherboard , typically range for L2 cache are 128kb - 1MB.

3. L3 Cache.

Usually , it is not used . This Cache is connected to the motherboard . This Cache is used for computer with high capacity . L3 is not necessary for all computer.

ROM(Read Only Memory):

Read only memory , in a sort , ROM is permanent memory of computer . Program are built into ROM at the factory level and cannot changed by the users . You can read them  , but can not alter . ROM's is non- volatile - the contents program that are 'firm' - not changeable. ROM is a non-volatile memory the content do not disappear when the current is turned off.

ROM is of the following type:

1. Programmable Read Only Memory (PROM)

2. Erasable programmable Read Only Memory (EPROM)

3. Electrical Erasable programmable Read Only Memory (EEPROM)

Virtual Memory

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