Memory is an essential part of the computer system because a computer cannot process any task without it. Memory is used to store data and instructions for performing specific tasks on the computer system. The computer memory is typically a storage space that is capable of storing and fetching data.
Memory is a set of several memory cells known as the building blocks of memory. Each memory cell has a unique index number or identification number known as the unique address of that specific memory cell. The CPU is responsible for selecting memory cells to read or write data.
The performance of the computer system depends on the memory and CPU. CPU cannot store programs or a large set of data permanently. They are only capable of storing basic instructions required to operate the computer. Therefore, it is mandatory to have the memory to run a computer system properly.
There are basically two types of computer memory:
• Internal Memory
• External Memory
RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.
ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to.
PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.
EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light. EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.
SRAM stands for ‘Static Random Access Memory’. It stores the data in a static form which means that the data remains in the memory as long as the computer system is on. SRAM is faster and more expensive than DRAM. It uses a matrix of six transistors and no capacitors. As the transistors do not need the power to prevent leakage, hence, there is no requirement to refresh SRAM again and again.
DRAM stands for ‘Dynamic Random Access Memory'. DRAM is widely used in computer systems. Previously, there was a single data rate (SDR) DRAM in computers. At present, computers are using a dual data rate (DDR) DRAM. DDR is also available in different versions such as DDR2, DDR3, and DDR4, which are more energy-efficient and are providing better performance.
EPROM stands for ‘Erasable Programmable Read-Only Memory’. It is an upgraded version of PROM. Unlike PROM, EPROM allows users to erase the stored data as well as rewrite the data. The data stored in EPROM can be erased by passing ultraviolet light for a particular length of time using an EPROM eraser.
EEPROM stands for ‘Electrically Erasable Programmable Read-Only Memory’. As the name suggests, this type of memory is programmed and erased electrically. Both programming and erasing of data takes around 4 to 10 milliseconds. EEPROM can be erased and reprogrammed for around ten thousand times.
