What is Memory Device in Computer.Basic Materials Of Computer Science.

 WHAT IS MEMORY DEVICE IN COMPUTER

Types of Computer Memory.

RAM vS ROM. 

Uses of memmory.

Primary vs Secondary Computer .

Computer memmory application.

Computer memmory longgivity.

Computer memmory data storage.

What is Floppy Disk.

Types of RAM & ROM .

Dvd Vs CD.

         

INTRODUCTION

Computer structure is not different for the human anatomy. Our entire body works like a computer. We memories works we do and its duration and size depend upon individual capacity. Computer also avails the facility of memory that helps us remember wOrk, Computer memory is more efficient and more reliable than human memory.

WHAT IS MAIN MEMORY ? 

In Generally Memory refers to the processes that are used to acquire, store, retain, and later retrieve information.Memory is the working storage of computer. This is a very important part of computer which stores data temporarily or permanently for future use. Memory is also called primary memory or main memory. Memory uses several space for storage that are definite in number called capacity or size of memory. The unit, that measures capacity of memory called byte. 

MEMORY CAPACITY 

Memory capacity is defined in terms of the number of bytes a computer system store. 

Memory capacity of a computer system is normally stated in terms of Kilobytes (KB) Megabytes (MB), Gigabytes (GB). 

CLASSIFICATION OF MEMMORY

Memory classification has been shown as under the chart 

 1.PRIMARY MEMORY 

Primary memory is a part of the CPU whereas The secondary memory is the external to the             CPU.The secondary memory stores the data and keep it even when the electricity to the PC is cut off whereas the primary looses its contents immediately.

 

2.SECONDARY MEMMORY

Secondary memory refers to storage devices, such as hard drives and solid state drives. It may also refer to removable storage media, such as USB flash drives, CDs, and DVDs. Unlike primary memory, secondary memory is not accessed directly by the CPU.

   The secondary memmory is employed for bulk storage (mass storage) of programs, data and other information system.It has much larger capacity than the main memory.Its Store software, assemblers, compilers, useful packages, large data files etc. The Secondary memory is non-volatile in nature.  

HOW COMPUTER MEMMORY WORKS

3.Cache Memory 

Cache Memory is a high speed storage unit. It is much faster than main memory. Cache age is extremely expensive compared to main memory. The characteristics of cache memory compared to main memory are as under 

1.Access time is less 

 2.Access speed is more

TYPES OF PRIMARY MEMORY 

Primary Memory is basically used for doing the computer's internal task. Primary is of two types from the technology point of view. These are (a) Analog Memory (b) Digital Memory .

Based on its working methodology, it can be classified as follows

1. Random Access Memory (RAM) : 

It is the part of the primary memory which is used by the computer for performing all jobs supplied by the user. Generally, all data stored here is based on charge, and hence is power dependent. In this case, the user has both read and write permission. At power off condition, the Ram looses all its contents permanently. Basically, RAM comes into use when the user uses the computer. Based on its functioning, Ram is of two types  

                  

• Static Random Access Memory (SRAM) : It is faster and hence costlier. For this reason, it is available in limited amount in the computer. (SRAM comprises only about 10% of total RAM). 
• Dynamic Random Access Memory (DRAM): This part of RAM is Capacitor based ana hence it needs to be recharged at frequent intervals of time to retain the information.This extra activity makes it comparatively slower than S-RAM. For this same reason, it is cheaper and is available in large amount in the computer.

2. Read Only Memory (ROM): 

This part of the memory is circuit based and all the instructions stores here uses (RAM and ROM) logic gates rather electric charge. This makes ROM non volatile and hence its contents are not erased due to power shutdown or due to human manipulation. The contents of ROM remain unchanged through its life. Generally, ROM stores instruction necessary for ensuring proper working to the computer. These instructions are never changed and are stored using hard. ware circuits. These instruction are called FIRMWARE.

     Types of ROM: 

1.  Programmable Read Only Memory (PROM) 
2. Erasable Programmable Read Only Memory (EPROM) 
3.  Electronically Erasable Programmable Read Only Memory (EEPROM) 

TYPES OF SECONDARY MEMORY 

Secondary memory is generally used by the users for storing large amount of information. Based on the methods of accessing information, secondary memory can be of two types-

1.SEQUENTIAL ACCESS STORAGE DEVICE 

In this type of storage device, the access time varies according to storage location because here information's are accessed sequentially. . It finds its application in prepara- tion of telephone bills etc.  

• MAGNETIC TAPE: Magnetic tape is the most popular storage medium for large data, which are sequen- tially accessed and processed.   The magnetic tape medium is a plastic ribbon, which is usually % inch or 4 inch wide, and 50 to 2400 feet long. It is located with a magnetically recording material, such as iron oxide or chromium oxide. Like audio or videotape, the magnetic tape used in and computer systems can also be erased reused indefinitely. 

2. DIRECT ACCESS STORAGE DEVICE

 This type of storage device is used in those application where information has to be accessed at random or directly. In this type of device, accessing of takes same any information time irrespective of its position. This system. type of device is used in reservation system.

    2.A. MAGNETIC DISK

Magnetic Disk  is the most popular storage medium for direct access secondary storeage.Due to their random access capability, magnetic disk are the most popular on line storage device.

A magnetic disk is a thin, circular plate/ platter made of metal or plastic, which is usually coatEd on the both sides with a magnetizable recording material. The disk itself is stored in a specially designed protective envelope or cartridge.

2.A.1. Floppy Disk : 

Floppy disks are made of thin , flexible plastic material. Here a read write head is available for each surface and the head physically touches the surface reading data. Floppy disks are portable, quite cheap, but have less storage capacity. 

Floppy disks are basicaly of the following types 

A.Single Sided Single Density (SSSD) 
B.Single Sided Double Density (SSDD) 
CDouble Sided Single Density (DSSD) 
D.Double Sided Double Density (DSDD)

The most commonly used variety of floppy disk is DSDD having a capacity of 1.44 MB. 

2.A.2. Hard Disk: 

Hard disks are thin circular disks made of a rigid metallic material and coated with magnetic oxide. A read and write head is available for each of its surfaces but to avoid friction, the head does not physically touch the surface of the hard disk. Because of their extremely high capacity and high speed , hard disk are costlier. For protection, hard disk is permanently housed inside the computer in a protective metallic jacket and for this it is also known as 'fixed disk'. Generally, hard disks have capacities in the range of gigabytes.

  2.B.OPTICAL DISK

Optical disk or optical media are mass storage devices with huge capacity. The advent of compact disk (CD), anon erasable optical disk, made it possible to develop a new low cost storage technology.

     An optical disk storage system consists of a rotating disk. Which is coated with a thin metal or some other material that is highly reflective. Laser beam technology is used for recording / reading of data on the disk. Due to use of laser beam technology, optical disks are also known as laser disks or optical laser disk. 

2.B.1. DVD

Stands for "Digital Versatile Disc." A DVD is a type of optical media used for storing digital data. It is the same size as a CD, but has a larger storage capacity. Some DVDs are formatted specifically for video playback, while others may contain different types of data, such as software programs and computer files.

  

       There are 3 common types of DVDs: DVD-5, DVD-9, and DVD-10. A DVD-5 is a single layer DVD that holds up to 4.7GB of data (around 120-133 minutes of video depending on compression). DVD-9 is a dual layer single sided DVD that holds up to 8.5GB of data (around 240 minutes of video depending on compression).

2.B.2. Compact Disk (CD): 

Compact Disks have got extremely high capacity of data storage and works very fast. It has got a long life, provided that it is used properly . generally, compact disks are used to store extremely important software. Here, data is stored optically on spiral tracks. At the time of recording some information in the CD, laser beam of very high intensity is made incident on the spinning disk.

• CD-ROM (Compact Disk Read Only Memory) 

The original, standard CD, CD-ROM stands for Compact Disc, Read-Only Memory. What this means is that you can only read information from a CD-ROM; you can't add new information in a way. 

 

• CD-R 

If you have a CD-RW drive you can permanently store information on a CD-R (Compact Disc Record able) disc. The information you write or burn to a CD-R is permanent and can't be changed or erased. You can also use CD-R discs to create musical CD's that you can listen to in a stereo system.