what is ram and rom - what is difference between ram and rom

There are several major differences between the ROM (read-only memory) chip and the RAM (random-access memory) chip. The difference revolves around uses, storage capabilities and capacities, and physical sizes of ROM and RAM chips. 

RAM and ROM

Memory is the most essential element of a computing system because without it a computer cannot perform simple tasks. Computer memory is of two basic types - primary memory (RAM and ROM) and secondary memory (hard drive, CD, etc.). Random-access memory is primary-volatile memory and read-only memory is primary-non-volatile memory.

What is RAM

RAM stands for Random Access Memory, It is also known as main memory placed in the central storage unit of a computer system. It is relatively large and fast memory and is used to store programs and data during computer operations. RAM is used to store all active programs and data: so that they are readily available and easily accessed by the CPU and other components of the CPU.

it is read-write memory In a Random Access Memory, any memory location can be accessed in a random fashion without regard to any other location. The access time is the same for each memory location.

Random-access memory is used to store programs and data that are being used by the CPU in real-time. Random-access memory data can be read, written, and erased at any time. RAM is a hardware element where the data currently being used is stored. It is an unstable memory is RAM

Two types of RAM

1. Static RAM:- The static RAM stores binary information using clocked sequential circuits. that stores a bit of data using the position of a six-transistor memory cell.
2. Dynamic RAM:- The DRAM stores binary information in the form of electric charges. that stores little data using a pair of transistors and capacitors that constitute the DRI memory cell.

What is ROM

A ROM stands for Read-Only Memory. ROM is non-volatile memory i.e. if the power supply is switched OFF, the content of ROM is as it is. It is used for permanent storage. The contents of a ROM is decided by the manufacturer. These contents are permanently stored in a ROM at the time of manufacturing. The user cannot write into a ROM.

A good example of a ROM is the computer BIOS, which is a PROM chip that stores the programming needed to start the initial computer startup process. Using a non-volatile storage medium is the only way for computers and other devices to begin this process. ROM chips were also used in gaming system cartridges, such as the original Nintendo, Gameboy, Sega Genesis, and others.  

Read-only memory (ROM) is a type of memory where data is predetermined. Data stored in ROM is kept even after the computer is turned off, ie non-volatile. Some portion of ROM is used for storing an initial program called the bootstrap loader. The bootstrap loader is a program whose function is to start the computer software operating when power is turned ON. ROM are of different types as follows

There are many types of  ROM 

1. Programmable ROM:- A PROM is a "Programmable Read-Only Memory". This is also non-volatile in nature and can be written only once using some special equipment. The writing process in PROM can be performed electrically by the supplier or the customer. After programming, that can be used as a ROM.
2. Erasable Programmable ROM:- An EPROM is an "Erasable Programmable Read-Only Memory". The contents are erased by exposing EPROM to high-intensity short wave ultraviolet light for 10 to 20 minutes. It can erase the bits stored in the chip. The chip can, therefore, be used again for storing some other information. There should not be overexposure. where data on this non-volatile memory chip can be erased by exposing it to high-intensity UV light.
3. Electrically Erasable Programmable ROM:- EEPROMS are "Electrically Erasable Programmable Read-Only Memory". They need not be removed from a microcomputer board for erasing. The change in contents is made in milliseconds which are much less than the erasing time of an EPROM. A typical time is 10 milliseconds for Motorola 2817. About 10 ms is required to write each byte of data into the device. A single byte of data or the entire device can be erased in about 10 If required single bit can also be erased. Erasing and programming of EEPROM is much easier as compared to EPROM.
4. Mask ROM:- In this ROM, a bit pattern is permanently recorded by the masking and metallization process. It is an expensive and specialized process. Memory manufacturers are generally equipped to do this process, but it is economical only for huge production. in which data is written during memory chip creation.

Different between RAM and ROM

Sr. No.	RAM (Random Access Memory)	ROM (Read Only Memory)
1.	Ram is volatile type of memory	ROM is non-volatile type of primary
2.	It is read/write memory	It is Read Only Memory
3.	It is used for temporary storage of data and instructions.	It is used for storing permanent start-up routines.
4.	It is used as a main memory of computer	ROM is used as a BIOS (Basic Input Output System)
5.	It is relatively large and fast memory and is used to store programs and data during computer operations.	The contents of a ROM are decided by the manufacturing.
6.	RAM is used to store all active programs and data	The contents are permanently stored in a ROM at the time of manufacturing.
7.	RAM can transfer data to and from the CPU for processing	ROM instructions are executed when computer started
8.	RAM are of two types Static RAM and Dynamic RAM	ROM are of two types Static PROM, EPROM, EEPROM and Masked ROM.