what is RAM and ROM | RAM aur ROM kya hota h

 Now we will learn about what is RAM and ROM. So let's get started...

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What is RAM (Random Access Memory) :

In the random-access memory (RAM) the memory cells can be accessed for information transfer from any desired random location. That is, the process of locating a word in memory is the same and requires an equal amount of memory, thus the name "random access".

Communication between a memory and its environment is achieved through data input and output lines, address selection lines, and control lines that specify the direction of transfer. 

The main drawback of RAM memory is that it is a volatile memory. That is, when power goes off, the contents of RAM get erased.

Types of RAM:

1. Dynamic RAM (DRAM) :

Dynamic RAM consists of transistor and capacitor that's capable of storing an electric charge. Depending on the switching action on the transistor, the capacitor either conatins no charge (0 bit) or does hold a charge (1 bit). The dynamic RAM provides volatile storage i.e., contents are lost in the event of power failure.

The amount of time taken to produce data required from memory, from the start of access untill the availability of data is called memory access time. Today's DRAM chips have access time ranging from below 7 to 70 nanoseconds.

DRAM storage density- Since a DRAM cell consists of only one transistor and capacitor per bit, it allows a DRAM chip to pack a large number of cells wiithin the chip compared to SRAM. Generally DRAM chips are available with 128 bit or 256 bit densities or even more.

DRAM refreshing- The problem of a capacitor is that it starts loosing the charge over a period of time, and can retain data for barely a thousandth of a second. Even a read-attempt also drains out the charge. Therefore, the memory controller needs to refresh the memory contents as many as thousand times a second, which is called memory refreshing. The refresh operation operation consumes precious processor time, because each refresh cycle takes several CPU cycles to complete.

2.Static RAM (SRAM) :

Static RAM is also volatile but as long as they are supplied with power, they need no special regnerator circuits to retain the stored data. The static RAM consists eventually of internal flip-flops that stire the binary information. The stored information remains valid as long as power is applied to the unit.

 Static RAMs take up more space for a given storage capacity than do dynamic RAMs. Static RAM are thus usedbin specialized applications while dynamic RAMs are used in the primary 

storage sections of most computers. The static RAM is easier to use and has shorter read and write cycles compared to dynamic RAM.

 

 

  Will be continued.....