Computers are used to process large volumes of data and to execute very complex programs. The computer needs to have some kind of storage device to hold these programs and data. Such as device should be directly accessible to the CPU and its speed must be compatible with the speed of the CPU. Also computer must be able to store frequently needed data on some permanent storage devices in computer.
Types of Storage Devices in Computer:
. Based on the characteristics of the storage devices we classify these devices as Main Memory and Secondary Memory storage devices. In this article we will describe both types of storage devices in computer briefly.
1. Main Storage Devices:
Digital computers are stored programs computers that mean a program to be executed is first loaded in the memory storage devices in computer and then instructions are executed one by one. The data and results of the calculations are also stored in the memory. In this sense main memory is the working area of the computer. It is very fast but limited in capacity. A computer cannot work without main memory. Most general purpose computer have enough memory to store a few million characters.
The main memory of a computer consists of thousands or even million of cells. Each cell capable of storing a bit that is 0’s and 1’s.These cells are logically organized into groups of 8 bits is called byte. Each byte has unique address assigned to it. This number is called the address of that byte. These scheme of arranging cells into a byte and bytes into memory chip.
2. Secondary Storage Devices:
Primary storage devices are directly accessible to processor and are used to store data and programs that are in current time. The control unit does not have direct access to data that is stored anywhere outside the processor or main memory. However this storage is limited in size and volatile. We need some storage devices that is not temporary in nature and that does not have the same restriction of size as that of main memory. Such a device is called secondary storage devices in computer. Secondary storage devices are categorized according to following:
- Data stored optically and magnetically
- Sequential and direct storage access technique used
- The capacity of the devices according how much we want it
- Easily portable and easily remove or change
Secondary storage is required permanently stone information that is not needed in memory all of the time and which may be too large to fit into the memory of the computer. Two main categories based n the ways of accessing data from a secondary storage are sequential Access and Direct Access or Serial Access and Random Access respectively.
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