Computer Memory
Memory is an essential component of any digital computer. It is storing device. It stores programs and data, which is required by the CPU, and the results generated after processing.
There are two types of memory are used in computers:
1.Primary Memory (Semi-Conductor Memory)
The Primary memory is the main memory of the computer. It stores the programs and data, which are currently needed by the CPU. The size of the main memory is comparatively much smaller than that of the secondary memory because of its high cost. The CPU communicates directly only with the main memory. As the CPU works at very high speed, its matching memory must be very fast. Only primary memory devices can provide the matching speed.
2. Secondary Memory ( Magnetic Memory)
The storage capacity of the primary memory is not very large, it cannot hold a large amount of data, including programs, which may be needed for processing. Thus, secondary storage devices are necessary. The secondary memory is used as auxiliary memory. The secondary memory is used for bulk storage or mass storage of programs, data, and other information. It has much larger capacity than main memory. The secondary memory retains the information once stored on it. The magnetic memory such as Hard Disk Drive (HDD), Compact Disk, Pen Drive, Memory cards is the most commonly used secondary memory in the computer.
3.Magnetic Disks
Magnetic disks are thin circular plastic plates on which some magnetic material is coated. Magnetic disks come in various sizes and materials. They use the properties of magnetism to store the data on a magnetic surface. A disk pack normally consists of such disks mounted on a central shaft. The central shaft rotates at speeds of about 7200 revolutions per minute (RPM). In a disk plate information is stored on both surfaces. The surface is further divided into a number of invisible concentric circles called as tracks. The tracks are further divided into various sections called as sectors.
4.Hard Disk
The most common physical device for storing files in the hard disk.The hard disk typically contains several rotating disk plates, which are permanently encased in a hard disk. The surfaces of the plates are covered by metal oxide; electromagnetic recording heads. It performs read/write operation. There is one head for each surface, and all the head move together.
5.Floppy Disk
Floppy diskette contains a single flat piece of circular plate (the disk) coated with metal oxide and enclosed in plastic cover. Floppy disks are small and portable. The three common sizes are 3.5”, 5.25” and 8” diameter.
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