Memory

 Computer:

            

                                      A Computer is a machine that accepts data from the user, processes it and gives output in return. It performs all computations with great speed and accuracy. It means, the user of the computer tells his problem to the computer through keyboard, computer through processing resolves it and returns it to the user, as well as stores it in memory for later use. Computer memory is very valuable feature. For example, as in our daily routine we save our things in a box, similarly, memory is a box where we store our data.

What is Memory?

                                                   Memory is like our brain. It stores our data and information. From memory we can retrieve our data in future, apply changings and update our data. We can store both input and output here. A memory is classified into two types of primary memory and secondary memory. Primary memory is computers memory. And secondary memory is like USB, Memory card etc.

Characteristics of Memory:

• Computers memory's speed is faster than secondary memory.
• It is volatile memory. It mean its content may destroy when computer shut down.
• It is compulsory for computer.
• It is the semiconductors memory.
• This memory is the main memory of the computer.

Different types of memory:

1.Secondary Memory
2.Primary Memory

1.Primary Memory:

Primary memory is also called computer's main memory. It stores the program during computer operations. In primary memory, semiconductors technology is used so it is called semiconductor memory.

It has two types:

1.RAM
2.ROM

1.RAM:

RAM stands for random access memory. It is volatile memory. It means its working depends upon power supply. If power supply suddenly of or interrupted, its content may lose. It may used for booting up the computer. It temporary stores the information during program.

It also has two types:

1.SRAM
2.DRAM

1.SRAM:

      SRAM stands for Static Random Access Memory. This type of memory uses transistors and circuits of this memory are able for retaining their contents

until the power supply exists. It takes less time to access any thing so it is faster memory. It consists of a string of flip flop and each flip flop stores one bit.

2.DRAM:

DRAM stands for Dynamic Random Access Memory. This type of memory uses transistors and capacitors. It stores data as a charge on to the capacitors. These capacitors contains many thousand of memory cells. Its disadvantage is that it is compulsory to refresh the charge on the capacitor after the some milliseconds. So, this type of memory is slow.

2.ROM:

 ROM stands for read only memory. This type of memory is non-volatile. It means if the power supply is sudden off or interrupted, its contents may not destroy. As its Read only memory, its contents are only readable. We cannot change, edit or modify its contents. It is used for important operations of computer.

It consists of some electronic fuses that may be programmed for a piece of the special information.

 And this information is stored on to the ROM in binary form. It is also called permanent memory.

It consists of four types:

• MROM
• PROM
• EPROM
• EEPROM

1.MROM:

              MROM stands for Masked rom.  A Hard-wired device with the pre-programmed collection of the data or the instructions were the earliest ROMs. Masked ROMs are the kind of the low-cost ROM that performs its works in this way.

2.PROM:

            PROM stands for programmable read only memory. The user can change this type of memory only once. The user buys a blank PROM and edit the data he wants on PROM. Then its contents become permanent.

3.EPROM:

             EPROM stands for Electrically Programmable rom. This type of memory is an extension to the PROM. And here you can remove the contents of ROM by exposing it to Ultraviolet rays for 40 minutes.

4.EEPROM:

                EEPROM stands for Electrically Erasable Programmable Read Only Memory. In this type of memory, the written contents can be removed electrically. You can also delete and reprogrammed EEPROM up to the 10,000 times. It takes very little time in erasing and reprogramming, For example, nearly 4 -10 MS (milliseconds). You can erase and re-programme any area of EEPROM of your choice. 

2. Secondary Memory:

Secondary memory is also called auxiliary memory. It is non-volatile memory; it means its contents do not destroy if power supply is interrupted. It is used for storing a large amount of data permanently. It is used to take the backup of data. We can store our data in secondary memory for a long time. The contents of secondary memory first stored in primary memory then CPU process it. But its speed is slow. 

Characteristics of Secondary Memory:

• This type of memory is slower than primary memory, but we can use it again and again.
• It is an easy to use and its contents do not destroy if power is off.
• Its cost is lower than primary memory.
• It can store a large amount of data than primary memory.
• This type of is not compulsory for computer like primary memory.
• The data of secondary memory is permanent.

Types of secondary memory:

1.Magnetic tape:

                             On this type, data is stored in magnetic form. It is used for backup. In this type of memory if we want the last song, we have to play all previous songs.

2.Magnetic Disk:

                               It is a circular disk on which data is magnetize. It is a type of memory on which we can access data from where we want. Its types are floppy disk Zip disk.