types of primary memory in computers


As human beings have a memory system to remember even a tiny thing which went through in one’s life, similarly computer systems do contain a memory system which can store data and can be retrieved when desired. Why not after all it’s been designed and created by intellectual humans only.  Every computer system contains two kinds of memory out of which one is primary and the other is secondary memory. Basically a computer memory can store particularly two things. They are the data and the set of instructions to execute a program.

Now let us take a brief look towards the types of primary storage (or) primary memory. This primary memory can be directly accessed by the processing unit. The contents in the primary memory are temporary. While performing a task if there is any power cut problems then we may lose the data which is in primary memory. One benefit is that we can store and retrieve the data with a considerable speed. Primary memory is more expensive when compared to secondary memory.

RAM (Random Access Memory) could be the best example of primary memory. The primary memory in the computer system is in the form of Integrated Circuits. These circuits are nothing but RAM. Each of RAM’s locations can store one byte [1 Byte = 8 bits] of information. This can be in either of the forms 1 or 0. The primary storage section is made up of several small storage locations in the integrated circuits called cells. Every single cell can store fixed number of bits called word length. Each cell contains a unique number assigned to it and it has the unique address; these addresses are used to identify the cells. The address starts at level 0 and goes up to (N-1).

Let me show you few things which are purely related to primary memory.The different types of primary memory in computers are as follows:

RAM [Random Access Memory]

RAM is the best example of primary storage. We have very good reason to justify because in this kind of memory we can select randomly, use that at any location of the memory, then store and finally retrieve processed data which is information. RAM is a volatile memory because it loses its contents when there is a power failure in the computer system. The memories which lose their contents on power failure are called volatile memories.

ROM [Read Only Memory]:

ROM is also formed by Integrated Circuits. The data which is stored in ROM is permanent. The ROM can only read the data by CPU but can’t be edited or manipulated.ROM is a non-volatile memory because it will not lose its contents when there is a power failure in the computer system. The basic I/O program is stored in the ROM and it examines and initializes various devices attached to the computer when the power is ON. The contents in the ROM can neither be changed nor deleted.

PROM [Programmable Read Only Memory]:

As we know that we cannot edit (or) modify data in the ROM. To overcome this problem to some extent PROM is very helpful that is in PROM we can store our programs in PROM chip. Once the programs are written it cannot be changed and remain intact even if the power is switched off. Therefore programs written in PROM cannot be erased or edited.

EPROM [Erasable Programmable Read Only memory]:

EPROM will overcome the problem of PROM. EPROM chip can be programmed time and again by erasing the information stored earlier in it. EPROM chip has to be exposed to sunlight for some time so that ultra violet rays fall on the chip and that erases the data on the chip and the chip can be re-programmed using a special programming facility. There is another type memory called EEPROM that stands for Electrically Erasable Programmable Read Only Memory in which we can erase the data and re-program it with a fresh content.


Actually computer system uses a number of memory units called registers. Registers store data or information temporarily and pass it on as directed by the control unit.

Flash memory:

It is a non-volatile computer memory that can be electrically erased and reprogrammed. Examples are memory cards, chips, pen drives, and USB flash drives etc. flash memory costs very less than byte-programmable EEPROM. It is very portable in nature.