Data Storage in Computers (Primary and Secondary Memories)

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Friends, in our previous post, we have studied how the computer takes data into the Binary System, today we shall see how the computer keeps data in various types of memory.

The greatest merit of a computer is data storage. The place where we keep data is called memory. As we already know, this memory is of two types. Those are,

1. Primary Memory (Main Memory) and
2. Secondary Memory

We can, however, compare the primary memory with our human mind. We can hold the information in the cells of our brain, and take it outside whenever the need arises. For example, we will store the address of a person called Shivani. Sometimes we will write the full address in a diary or a notebook thinking that we may forget it at any time. Then suddenly one of our relatives may ask for the address of Shivani. If we remember it in brain, we will tell it. Here the information given by the brain is called primary memory in the computer terminology.

If you don't remember the proper address and you take the address from the note book, it is termed as secondary memory. As the mind is primary, it is called primary or main memory. As we can not remember long names and numbers, we write in a diary or note book permanently. So it is called Secondary or Permanent memory. 

We will study in detail the above two types of memory. 

Primary Memory

This Primary Memory is again divided into many small parts. These small parts are called memory cells. The computer will fill-up the information given by the users in these cells.

Every cell has an address. Why do we need this address ? Whenever we want to access data from the memory, we have to refer to the address of the cell where data is stored. We can also keep additional information in that cell and we can open that cell to see the data or information contained in it.

Sometimes while working on computer, the power supply may go off. Then what happens to the information ? Suppose we are storing information in the primary memory and suddenly the power goes off, we may lose all the information. To avoid this loss and safeguard the information, secondary memory is used.

RAM and ROM

The Primary Memory in the computer is divided into two parts. Those are,

1. Random Access Memory (RAM)
2. Read Only Memory (ROM)

We will now discuss these two memories in detail.

ROM (Read only Memory)

When we open the computer, a system start up (we call this Booting) process begins. These contents are written in memory at the time of manufacture and they can not be changed by the user. This type of memory is called ROM (Read only Memory). This information is not lost even though the computer is switched off. As it is not lost, it is called Non Volatile Memory. This can be compared with the original thoughts and opinions that are fixed in human mind.

Now a days we have the extensions of this ROM, namely PROM and EPROM.

PROM (Programmable ROM)

As the name indicates, this type of memory can be written only once by the user or programmer. Thereafter it can not be changed by the user.

Erasable Programmable ROM (EPROM)

In this type of memory, we can modify the contents of PROM as many times as we want. This type of memory can be modified using ultraviolet light.

RAM (Random Access Memory)

This type of memory can be read and written by the user. It is called RAM (Random Access Memory) because any place on a chip can be selected at random and used to store programs or data. It deals with current information that we are working on. For example, if we want to add some numbers, they will be contained in RAM. Suppose again we want to type a letter, this new data can be entered into RAM. But when the computer is switched off, the information contained in this memory is completely lost. That is why it is known as "Volatile Memory". So before you switch off the computer, it is better to save the information. This RAM can be compared with the temporary thoughts and opinions in our mind which change frequently.

Secondary Memory

In order to store the information permanently in the computer, as you know secondary memory is the solution. The information stored in the secondary memory is called Saving of Information. The computer in this case will ask for the file name. Whenever you type the name of file, it will be saved in that file permanently.

Once the files are saved, the computer will reproduce it as and when demanded. We can make changes in that file. There will be no loss of information even when power goes off. Normally, secondary memory is stored in Hard Disc, CD Rom or Pen Drive.

That's all for now friends. In our next post we shall discuss about the Data Storing Devices in Computers. Happy Reading :)

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