How many types of computer memory?

Describe the different types of computer memory

Memory is the place to hold memories or information. Information can be stored here. Memory is mainly of two types,

(a) Main memory/Primary memory

(b) Auxiliary memory/Secondary memory

Main memory is again of two types, namely--

(i) RAM or Random Access Memory

(ii) ROM or Read-only memory (ROM or Read-only memory).

1. Main memory/ Primary memory: The memory with which ALU has a direct connection is called the main memory. The main memory also needs to be very fast as it is directly connected to the ALU and capable of very fast calculations. All the information and instructions that are always needed are kept in the main memory. In addition, the necessary data and instructions for the calculations performed by the ALU are fetched from the auxiliary memory and temporarily stored in the main memory. After the calculation is finished they are moved back to the auxiliary memory.

Main memory is of three types namely-- 

(a) Internal, (b) External and (c) Read Write (R.W.) Memory.

Internal memory is inside the microprocessor. The ALU communicates with this first. There are two types of external memory, namely RAM and ROM. These are some of the markings on the outside of the microprocessor on the motherboard. A program or data comes to RAM before coming to ALU, then comes from RAM or ROM to internal memory. After the operation of ALU, internal memory goes to RAM or an external device. Read Read Write Memory can be both read and written like Data RAM, but it is a permanent memory.

2. Auxiliary memory/Secondary memory: Auxiliary memory is used to expand the working area of ​​the computer. It is also known as external or secondary memory. Auxiliary memory stores the main processing results and some necessary programs. It is a non-destructive, modifiable emulator with additional space in addition to the main memory provided by auxiliary memory. Its capacity is much larger than the main memory. Here only data and instructions can be stored. No processing operations are organized into it. It is slower than the main memory. It should be noted here that in computer processing work takes place in main memory and storage work takes place in auxiliary memory. Auxiliary memory includes magnetic tape, floppy disk, hard disk, magnetic drum, etc. Auxiliary memory contains information and instructions that are not currently needed for computation but will be needed shortly. Since there is no direct connection to the ALU, it is slightly slower, but not too slow. Because data and instructions are always moving between auxiliary and main memory.

The storage capacity of auxiliary memory is much larger than that of main memory. Because it contains all the information and instructions needed for calculations shortly. The cost per bit is also lower as it is slower than the main memory. As a result, the storage capacity is high but the auxiliary memory is not redundant. Its access time is milliseconds.

RAM: It is a temporary memory. The data we input is first stored in RAM. Then the processor processes the data from the RAM and returns it to the RAM. Then we see it on the monitor. All data is deleted when the computer is turned off. RAM capacity can be 4 GB or more.

ROM: The part of the computer which is provided by the company, under the instructions of which the computer is operated, is called ROM. As soon as the computer is turned on, the ROM checks all the hardware and creates the working environment by fetching the operating system from the hard disks. If no hardware is found, it returns the signal.

Classification of ROM:

Based on the data storage technique, ROMs can be divided into the following categories, namely--

1. MROM (MROM Mask Programmable Read Only Memory)

2. PROM or PROM (PROM Programmable Read Only Memory)

3. EPROM or EPROM (EPROM Erasable Programmable Read Only Memory)

4. EEPROM or EEPROM (EEPROM Electrically Erasable Programmable Read Only Memory)

5. EAPROM (EAPROM Electrically Alterable Programmable Read Only Memory)

1. MROM (MROM Mask Programmable Read Only Memory): Information is stored in it by a program using photographic masks. Usually, EMROM is programmed by the company according to the user's needs. It is quite expensive. However, the use of many programs with similar programs is economically viable. Once programmed it cannot be re-programmed.

2. PROM or PROM (PROM- Programmable Read Only Memory): Usually the disadvantage of ROM is that the user cannot change the program at will or write a new program. But not all the programmed ROMs available in the market work. In these cases, prom is used. In this method, the user can convert his own program into a microprogram and store it in PROM. Newer ones available in the market have one fuse in each cell. As a result, all cells in a newly purchased prom contain binary 1s.

With a special PROM program, the user can reset the PROM to 0 by blowing fuses in special memory cells. In this way, the user can store his written microprogram in PROM. Once the PROM is programmed, the information stored in it cannot be changed. That is, the PROM then becomes ROM and the information stored in it can only be read. Like Saram Nyaya Pram is also non-volatile, i.e. the data stored in it is not erased when power is turned off. Special PROM program tools are available for programming multiple ROMs in the same program.

3. EPROM or EPROM (EPROM-Erasable Programmable Read Only Memory): Once the information is stored in ROM or PROM, it cannot be changed. So to remove this problem a special type of ROM has been developed which is called EPROM or EPROM. Data stored in EPROM can be erased and reprogrammed with a special program. Eprom has a small quartz window through which the silicon wafer can be seen. While erasing the stored data, UV rays fall on the silicon wafer through a ramp window that holds the EPROM under an ultraviolet lamp. As a result, the e-prom information is deleted in no time. Later, the data can be saved to EPROM again with the help of the PROM program. EPROM is non-volatile i.e. the programmed data is not erased by turning off the power supply. Generally, EPROM is made using FET (FET-Field Effect Transistor).

4. EEPROM or EEPROM (EEPROM Electrically Erasable Programmable Read Only Memory): The disadvantage of EEPROM is that it takes about half an hour to erase the information stored in it and no information can be partially erased. EEPROM was developed to overcome this difficulty. It can easily be erased and reprogrammed with all the information stored in it or one or more bits as required by the current. That's why its name is Electrically Erasable Programmable Read Only Memory abbreviated EEPROM. It has to be opened from the computer while programming. It takes much less time to erase the data stored in it than EPROM.

5. ERAM (EAPROM-Electrically Alterable Programmable Read Only Memory): Like EEPROM, any bit of PROM can be erased and reprogrammed by an electric current. However, it is not necessary to remove the text from the computer while erasing it.

Classification of RAM: According to the operating mode RAM can be divided into two parts namely--

(A) Static RAM and

(B) Dynamic RAM

Static RAM: Static RAM is made up of flip-flops that hold binary registers 0 and 1. The data stored in it remains in the memory as long as there is a power supply. Data stored in the memory is erased when the power supply is turned off. Static RAM is very fast so it is used for video RAM, cache memory etc.

Dynamic RAM: In dynamic RAM, binary bits 0 and 1 are stored in capacitors in the form of electrical charges. If the capacitor is charged, the 1 state, if not, means that the capacitor's charge is slowly dissipated even when the power supply is present. So every few milliseconds the information written in each memory cell has to be rewritten with the help of the RAM controller. In capacitor terms, this is called memory refresh. Dynamic RAM is usually used as the main memory in microcomputers.