RAM stand for Random Access Memory. It is also called direct access. Random Access means that each individual byte in entire memory can be accessed directly. RAM is used to store data and instructions temporarily.
RAM is volatile. It means that data are lost when power is turned off. RAM is a Read/Write Memory. CPU can read data from RAM and write data to RAM. It is used to store data and instruction while data to RAM. When a computer is turned on, the data transfer from Hard disk to RAM. It also called main and primary memory.
Types of RAM build by using two different techniques:
It stands for Dynamic Random Access Memory and type of RAM used in most of the computer. It is least expensive kind of RAM.
DRAM requires an electric current to maintain its electric state. The electric charge of DRAM decreases with a time that may result in loss of data. It is recharged or refreshed again and again to maintain its data. The processor cannot access the data of DRAM when it is being refreshed. That is why it is slow.
It stands for Static Random Access Memory. The memory cells are made from digital gates. Each cell can store data without any need of frequent refreshing. CPU does not need to wait to access data from SRAM during processing. That is why it is faster than DRAM. It utilizes less power than DRAM. SRAM is more expensive. Cache memory is an example of SRAM.
It is a type of SRAM. A cache (pronounced “cash”) is a small and very fast memory. It is designed to speed up the transfer of data and instructions. It is faster than other memories. The data and instructions that are most recently or most frequently used by CPU are stored in a cache.
The data are retrieved from RAM when CPU uses them for the first time. A copy of that data is stored in a cache. The next time the CPU needs that data, it first locates in the cache. If required data is found there, it is retrieved from a cache instead of main memory. It speeds up the working of CPU.
ROM stands for Read Only Memory. The instruction in ROM prepares the computer for use. These instructions can only be read but cannot be changed or deleted. It is not possible to write new information or instructions into ROM.
It stored data permanently. When the power switched off, the instructions stored in ROM are not lost. That is why ROM is known as non-volatile. The information in ROM is stored by the manufacturer. When the computer is switched on, the instruction in ROM is automatically loaded into RAM.
There are Four types of ROM which are listed below:
It stands for Programmable Read Only Memory. This form of ROM is initially blank. The manufacturer or user writes data and program on it using the special device only once. If any error found, it cannot be removed from it. The chip becomes unusable.
It stands for Erasable Programmable Read Only Memory. It is blank initially and then user or manufacturer writes data and program on it using a special device. Data written on it can be erased with a special device using ultraviolet rays which are the complicated task. Then the user will able to write new data.
It stands for Electronically Erasable Programmable Read Only Memory. In this types, a user can erase and write with the help of electrical pulses. If there is any error in a program, the user can erase content electronically. It is easy to modify content.