Computer Memory 2nd Part | Lesson 3

"ফাইল ডাউনলোড করার জন্য নিচে স্ক্রল করুন"

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Computer Memory 2nd Part | Lesson 3

Hard Disk :

Hard-disks are used to permanently store large amounts of data in computers. A hard-disk consists of a series of thin, hard aluminum alloy spherical discs called platters. Both sides of the disk are covered with a coating of magnetic material. Hard disk has more data capacity than a floppy disk. That's why the price of hard disk is much higher than floppy. Hard-disk drives are kept inside a computer by placing them inside a metal jacket to protect the thin metal disks. That is why it is called a permanent disk.

Advantages of using hard disk :

• Hard-disk is much larger in size than floppy so it has more data storage capacity.
• Hard-disk has a longer data storage life than floppy.

Remember : The Operating System along with any other software used to manage the computer is loaded on the hard disk. A new hard-disk needs to be formatted before it can be used.

Size :

Currently hard-disks are available in different capacities. Like 40 GB, 80 GB, 512 GB starting with 1Terabyte data storage capacity.

CD (Compact Disk) :

In addition to floppy and hard-disk in modern computers, CD or compact disk has become very popular for permanent data storage. The compact disc was developed in 1987 by a joint venture between Philips and Sony. It is used to store computer data as a secondary storage device (device). The use of CD revolutionized the computer world. CD is a type of optical disc.

Shape :

CDs are shaped like round discs. They are made of thin plastic. It looks like a listening record.

CD Types :

A large amount of data can be stored on a CD and the data is not easily lost. So the use of CD is increasing day by day. CDs can be broadly divided into two categories. A type of CD in which once data is written, the CD cannot be used to retrieve data. That is, the information on these CDs can only be read. That is why the word CD-R is written on this CD. Those called non-rewritable CD (Non-Rewritable CD).

Another type of CD in which after collecting data, the data can be deleted and re-written if necessary, that is, both data can be written and read in such CDs. These CDs have the word CD-RW written on them. These CDs can be used for a long time. These CDs are called Re-Writable CDs. A single CD can store 650 MB to 700 MB of data.

Advantages of using CD-ROM :

1. A laser beam is used to read and write information on a CD. Therefore, no read/write heads touch the CD. That's why the data on CDs remains intact as there is no friction when reading or writing data over and over again.
2. CD-ROM, such as hard-dick and floppy dicks, is not written with the magnetic field, and the information inside the CD-ROM does not lose contact with a magnet.
3. CD-ROM is made of light plastic so it is not difficult to carry.
4. Information can be stored in it for a long time.
5. Write data to CD very quickly and read data from the CD. Besides, its use is essential for fast data transfer from one place to another. The most important thing is that CD's usage is increasing day by day as the cost is very low.

CD DRIVE :

CD-DRIVE is used to read data inside any CD-ROM. These DRIVES are connected to the computer CPU.

CD-WRITER :

CD-WRITER is used to write and read data on a blank CD. CD-WRITER can both extract data from and write data from a re-writable CD.

Today, with the advancement of technology, the use of CD-WRITER is increasing day by day. As the price of CD WRITER is decreasing day by day, the use of CD-WRITER is increasing instead of the common CD-DRIVE.

DVD :

The full name of DVD is Digital Versatile Disk. It looks just like a compact disc. A DVD can usually hold between 4.7 GB and 17 GB of data. Nowadays DVD is mostly used in movies, video games, technology. This is because a DVD can store five or more data files at once, whereas a typical CD stores only one data file.

Currently DVD-WRITER is introduced to write or read any information on DVD. DVD WRITERs look just like CD-WRITERs, but write or read data to DVDs instead of CDs.

Cache Memory :

Today's computers require the use of complex software to store data rapidly. Cache memory is extremely fast. Current motherboards include this extra memory to help meet this need.

Data Storage Unit :

A unit used to measure any solid or liquid. For example, gram or kilogram for measuring weight, meter/kilometer for measuring distance etc. Similarly, the unit used to measure computer memory is called Byte. A byte is the smallest unit of computer memory.

Bit :

We need to know that computer can read and understand only two numbers. One is '0' (zero) the other is '1' (one). These two numbers are called binary digits or bits for short. All information stored in computer memory is stored as binary digits 0 and 1.

Byte :

Eight consecutive bits are combined together to form a byte. Byte is the smallest unit of computer memory. Each character used in a computer is considered as a byte.

Nibble :

When four bits (Bit) come together to form a word, it is called nibil.

Measurement of any sound in computer:

A computer stores data in memory using millions of bytes. Because the amount of stored data is very large, we express bytes as kilobytes, megabytes and gigabytes. Below is a mathematical solution to illustrate the point:

1024 bytes = 1 kilobyte (KB)

1024 kilobytes = 1 megabyte (MB)

1024 megabytes = 1 gigabyte (GB)

1024 GB =  Terabyte (TB)

ASCII

ASCII stands for American Standard Code for Information Interchange. Data from one computer needs to conform to a specific coding standard to be used as input data to another computer. So today almost all computers use ASCII code to express data. ASCII is the most popular coding system in the computer world. In ASCII code one is expressed by 7 bits. So a code represents a character.

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