WHAT IS COMPUTER "MEMORY"
by sumit kumar
Type of computer memory - Computer Knowledge
It is an internal storage area in the Computer System.
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Introduction of Memory
It is an internal storage area in the Computer System. the term Memory is used for physical memory, which refers to the actual chips capable of holding data. There is also a virtual memory, which expands physical memory into a hard disk. There are two types of memory use in Computer Primary and secondry.
The term memory can be categories in two ways.....
- Primary Memory : Every Computer comes with a certain amount of physical memory. usually referred to as min memory or primary memory for example RM and ROM.
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- Secondary Memory : These types of memories are internal or external devices either inside or outside the Computer. It store programs and data permanently. It is slower, but cheaper. Floppy disk, hard drives, CD, DVD pen drive etc are secondary storage devices. The secondary storage can be divided into Magnetic device, optical Device and Flash memory.
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RAM (Random Access Memory)
It is a temporary (Volatile) storage area utilized by the CPU. Before a program runs, the program is loaded into the memory which allows the CPU direct access to the program.
SRAM : Abbreviation is Static Random Access Memory that is faster and more reliable than the more common DRAM (Dynamic RAM). The term Static is derived from the fact that it doesn't need to be refreshed like Dynamic RAM. SRAM is often used only as a memory cache usually found in the CPU (L1, L2 and L3 Cache).
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DRAM : Stands for Dynamic Random Access Memory, a type of memory used in most personal Computers.
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DDR2- SDRAM : Abbreviation is Double Data Rate Synchronous DRAM 2 is a type of DDR that supports higher speed than it's ancestor DDR SDRAM.
DDR3- SDRAM : Abbreviation is Double Data Rate Synchronous DRAM 3 is the newest type of DDR that supports the fastest speed of all the SDRAM memory.
ROM (Read Only Memory)
Computers always contain a small amount of Read-Only Memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. It is non-volatile which means once you turn off the computer the information is still there.
PROM (Programmable Read-Only Memory)
A PROM is a memory chip on which data can be written only once. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process.
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EPROM (Erasable Programmable Read-Only Memory)
It is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased.
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EEPROM (Electrically Erasable Programmable Read-Only Memory)
Pronounced double-EE-Prom or e-e-prom, an EEPROM is a specil type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not aas fast as RAM. EEPROM is similar to flsh memory (sometimes called flash EEPROM).
BOOTING
Booting is the starting process of an operating system. This is a term we refer as what the computer is now will get ready to take command first of starting the operating system and afterward as per the user. Familiarly there are two types of booting the first one is Cold booting and the another is warm booting. In the Cold booting, a computer is started manually after pressing the power button of the CPU whereas a computer at its running condition is pressed a reset button to restart it then that one is known as Warm booting.
When you press power button to start or boot a computer system then it loads the necessary building block files and resources to the main memory afterwards when this process get ends then you can now surf the computer system.
The booting process includes loading of BIOS (Basic Input Output System) files and resources from ROM (Read Only Memory) to the main memory RAM ( Random Access Memory ) where when it gets ready, you can work ahead on the computer system and when yu turn off the computer system, all the files and resources loaded get erased from RAM whereas ROM keep and retain the information regarding the boothing process even after the power is off.
The BIOS first does POST (Power on self test) testing about the resources and devices attached to the computer system wheather those are in good conditions or not and functioning proper or not.
There are few of the building block files used to start or boot and operating system, in windows there is a file named Win.ini and Autoexec.BAT in DOS.
STORAGE UNITS
Storage units are considered as memory devices used to store data permanently. A storage device can be a Hard disk, Flash drive, Floppy, Optical disk, Zip drive etc. These storage devices are used to access or mobile the data to anywhere, to any computer system.
Here are some examples of Storage units.....
- Hard disk
- Flash drive
- Floppy
- Optical disk
- Zip drive
Secondary Storage Devices
Theseare another memory devices non-volatile in nature used to keep or store the data permanently to that you can access anytime when attached to the computer. You can not store the data in primary memory permanently and primary memory costs higher than primary memory whereas the secondary memory devices are cheaper comparetively. There are many secondary storage drives available to store the data permanently like floppy disk, Optical disk, Magnetic disk, Flash drives etc.
FLOPPY & HARD DISK
Floppy or Hard disk are based on Magnetic disk technology. In Floppy there is magnetic tape whereas there are track and sector functions like a magnetic disk. here are the detailed description...
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FLOPPY DISK
it is removable device or data traveler and re-writable. Floppy disk is flat, circular piece of Mylar plastic that rotate within a jacket. The circular plastic film is divided into track and sector. It is also known as diskette. the size of Floppy is 3.5 inches and the storage capacity of Floppy disk is 1.44 MB.
A Hard disk is a Magnetic disk made of metal and covered with a magnetic recording surface. Drive is the main location where all data is stored. Most hard disk drives consist of spinning platters of aluminum, glass or ceramic that is coated with a magnetic media. A single hard disk usually consists of several platters. Hard disk are used to store huge amount of data permanently. Now-a-days there are huge capacitive Hard disk available in the market to store the data like 500GB, 1TB and even greater.
There have been kind of Hard disk like Internet and External. Internal Hard disk is set and fitted inside the computer system whereas External Hard disk is accessed through outside using a USB port.
Each platter requires two read/write heads, one for each side. All the read/write heads are attached to a single access arm so that they cannot move independently. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder. It measured in MB, GB and TB etc.
The Hard disk drive has following components...
Platter
The actual fixed disk within the hard disk drive; there cn be several platters within the hard drive. In the center of the hard disk, there are platters which hold all of the data on the hard disk. A disk can contain one or more platters depending on the capacity. platters are round with a hole in the center- similar to a record used on a record player. A spindle with a motor holds the platters together and rotates them at a certain speed measured in RPM (revolutions per minute). This creates air pressure that lifts the read/write heads off the platters.
Heads : All the heads are attached to a single head actuator, or actuator arm, that moves the heads around the platters. Older hard drives used a stepper motor actuator, which moved the heads based on a motor reacting to stepper pulses.
Actuator
The actuator moves the actuator arm to the correct position on the platters using voice coils motivated by electric currents. When no electric current is being received, the actuator causes the actuator arm to place the read/write heads in the parked position.
Tracks
Large sections that completely circle the platter, just like there are grooves (tracks) on a music record, there are also tracks on each platter. These tracks are evenly spaced across the platter's surface.
Sector
The platter is divided into pie-shaped slices, called sectors, Now the confusing thing about sectors is that where a track intersects with a sector, sector are created- also known as sectors! Each sector (block) - 512 bytes in size- is the actual storage area for data.
Cluster
A group of sectors makes up a cluster, which is the allocation unit for a file- meaning wher a file is saved. When a partition (a logical division of space on the disk is formatted, the file system determines the cluster size based upon the partition size. For example, a 2GB FAT partition uses a 32k cluster size, That same 2GB partition formatted as FAT 32 uses only a 4k cluster size.
Cylinder
All platters in the hard disk contain the same number of tracks, but that number varies from one hard disk to another. These tracks are numbered from the outside in, starting with 0 (zero) For examples, on a platter with ten tracks, the track closest to the outer edge of the platter is track 0, and the track closest to the center is track 9.
Optical Disk CD ROM
This kind of storage devices come under secondary storage devices whereas CD-ROM is the driver to access or read an optical disk. Here arre the full details....
Optical Disk
It isa n advanced technology for dt storage. Optical disk read and written by laser beam. Optical disk does not need to move access arms and read/write heds, because a laser beam can be moved electronically. For writing dt, a laser bem burns tiny cavities into the surface of disk to mark bits for data. To read the data, a laser beam scans these areas.
There are kinds of Optical disk available....
Write Once Read Many Disk (Normal CD)
This kind of optical disk are plain and simple and easy to write the data once only and that ofter you can not re-write that disk ever but you can access or read it many times you want. This kind of optical disk contain upto 700 MB data.
Re-writable Optical Disk
This is an optical disk that can be erased and written upon repeatedly. An erasable optical disk has a great deal of data capacity. This kind of optical disk cost little higher than normal CDROMs.
CD-ROM (Compact Disk Read Only Memory)
This kind of Secondary memory device is an optical disk that is written upon once only by the user's environment and then cannot be re-written. It is situated at front panel of the CPU and set inside with face outside along with an open/close button. As per the optical disk technology, this access the data through random address and integrates the data packet accessed randomly.
DVD (Digital Video Disk)
It is even known as Digital Versatile disk. It is mass storage disk nomes normally upto 4.7 GB and in special case it comes even upto 45 to 50. This uses digit al technology to store data in concized form. It stores more than a normal compact disk. It looks similar as Compact disk but has grater storage capacity. DVDs can not be read or accessed by a CDROM drive because it has pits.
Mass Storage Devices
Mass Storage device is referred as the storage device which can hold more data than normal storage device.
USB Thumb drive
USB thumb drive normally known as flash drive or pen drive is used to store bulk data as per its capacity. They are small in size with a USB face is portable to be used any where any computer. This is little faster comparetively. This is a plug n play device which you do insert in the USB port of computer, do the data transaction and remove from that computer and can use it to other one that's why most of time it is even known as Data Traveler.
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