What is RAM and ROM ? Difference between them along with their types

There are available several types of memory to store the computer's data. Primary memory is part of the memory of the computer. Primary/internal memory is basic for all computers. Both RAM and ROM are the primary / internal memories of the computer. Where RAM is used to temporarily store the data. And ROM data is used permanently to store data. There are many differences between RAM and ROM, so let's start.....

What are RAM and ROM

What is RAM(Random Access Memory):

RAM memory which is also called random access memory. It is called random access memory because here random access means that CPU can directly access any address location of RAM. It is very quickly accessible. RAM is a volatile memory, it stores the data till the power is switched on, once the power goes off the whole data in RAM gets erased and it only stores data which has to be currently processed. 

The storage capacity of RAM is high ranging from 64 MB to 16GB. RAM is the fastest and costliest memory of the computer because of its speed. It is very expensive. It is a read-write memory of the computer which means the processor can read the instructions from the RAM and write the result to the RAM that's how data can be modified in RAM.

Type of RAM:

Two types of RAM are available

1). Static RAM

2). Dynamic RAM

1). Static RAM:  

Static RAM is one which requires the constant flow of the power to retain the data inside. Here the interrupted power could result in loss of data. The static RAM is made up of transistors and latches. Static RAM is faster and more expensive than dynamic RAM. It is mainly used as cache memory for the computer.

2). Dynamic RAM: 

Dynamic RAM needs to be refreshed to retain the data it holds because the capacitor is used in the construction of Dynamic RAM and capacitor has a charge leakage property that's why Dynamic RAM requires a separate refresh circuit. It is slower and cheaper than static RAM and it is highly dense.

What is ROM(Read-Only Memory):

ROM is also called read-only memory. Unlike RAM, ROM memory can't be directly accessed by CPU the data first transferred to the RAM and the CPU can access that data from the RAM. ROM is a non-volatile memory. The information inside the ROM holds regardless of whether the intensity of the CPU is turned off. The limit of ROM is similarly littler than RAM.

It is slower and cheaper than RAM. The data in ROM can only be read by a CPU that's why it is said read-only. The data in ROM cannot be modified. ROM stores the instruction that a computer requires during bootstrapping*.

[ * Bootstrapping is a self-starting process where the basic software's are loaded into the computer memory after power on or on a reset]

Type of ROM:

Basically, there are available three types of ROM

1). PROM ( Programmable ROM )

2). EPROM ( Erasable and programmable ROM )

3). EEPROM ( Electrically Erasable and Programmable ROM) 

1). PROM ( Programmable ROM):

PROM can be modified only once by the user the parent chip have small fuses which are burned open during programming that's why it is not erasable.

2). EPROM ( Erasable and programmable ROM ): 

EPROM(erasable and programmable ROM), the content of this ROM can be erased using ultraviolet rays and the ROM can be re-programmed during programming. An electrical charge is trapped in an insulated gate region the charge can be retained for more than 10 years because the charge has no leakage path. For erasing, discharge ultraviolet light is passed through a quartz crystal window for about 40 minutes this exposure to ultraviolet light dissipates the charge.

3)EEPROM ( Electrically Erasable and Programmable ROM): 

EEPROM can be erased electrically and pre-programmed about 10000 times both erasing and programming in EEPROM takes about 4 to 10 milliseconds. It is flexible because any location in EEPROM can be selectively erased and programmed but only one byte is erased at a time rather than entire the chip that's why it is kind of slow.

Difference between RAM And ROM:

1. RAM stands for random access memory whereas ROM stands for read-only memory.
2. RAM is readable and writable on the other hand ROM is only readable
3. RAM is used to store the data that has to be currently processed by the CPU temporarily in contrast ROM store the instruction required during the bootstrap of the computer.
4. RAM is a volatile memory as against ROM is a non-volatile memory.
5.  RAM sizes from 64 MB to 16 GB on the contrary, ROM is comparatively smaller than RAM.
6. There are two types of RAM static RAM and dynamic RAM whereas ROM has three types PROM, EPROM, and EEPROM.
7. Ram is a very expensive memory while ROM is comparatively cheaper than RAM.
8. Data in RAM can be modified conversely data in ROM cannot be modified.