Computer Memory

A computer is an electronic machine. It works very fast. It works by following the Input-Process-Output cycle. It accept input, processes it and gives the result. A computer receives data or instructions through input devices. The entered data is processed or changed into meaningful information by the CPU. The results of processing are displayed through the output devices.

Just we have a memory to remember things, a computer also have a memory. A computer uses its memory for processing and storing data and instructions. However, we tend to forget things over time, but a computer can keep on storing data for years. This data can be retrieved from the computer’s memory as and when required.

 

Measuring Computer Memory:                                                            

There are different units of measurement such as grams and kilograms for weighting, meters and kilometers for distance. Similarly, there is a unit for measuring the computer memory.

A computer can understand only the binary language. This is because a computer is an electronic machine and can understand only two states – ON (represented by 1) and OFF (represented by 0). Binary language consists of 0s and 1s. These binary digits – 0s and 1s are called bits.

The data is stored in the computer memory in the form of bits or binary digits. The capacity of a computer memory can also be expressed in terms of bytes. A combination of eight bits makes up one bytes. There are other bigger units of measuring memory given below:

UNIT	ABBREVIATION	STORAGE
Bit	B	Binary Digit, Single 1 or 0
Nibble	-	4 bits
Byte	B	1 Byte = 8 bits
Kilobyte	KB	1 Kilobyte = 1024 bytes
Megabyte	MB	1 Megabyte = 1024 KB
Gigabyte	GB	1 Gigabyte = 1024 MB
Terabyte	TB	1 Terabyte = 1024 GB
Petabyte	PB	1 Petabyte = 1024 TB
Exabyte	EB	1 Exabyte = 1024 PB
Zettabyte	ZB	1 Zettabyte = 1024 EB
Yottabyte	YB	1 Yottabyte = 1024 ZB

 

Types of Computer Memory:

You can remember things because they are stored in your memory (brain). Similarly, a computer has memory to store data and information for future use. Computer Memory are two types:

1. Primary Memory/Main Memory
2. Secondary Memory

1. Primary Memory or Main Memory:

Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and it is directly accessible to the CPU.

Characteristics of Main Memory:

1. These are semiconductor memories
2. Usually volatile memory because data is lost in case power is switched off.
3. Faster than secondary memories.
4. A computer cannot run without primary memory

It is divided into two subcategories RAM and ROM.

Random Access Memory (RAM):

RAM is a type of memory which is readable and writable. CPU can read and write the information to this primary storage area through RAM. RAM is volatile as any interruption in power supply results in loss of data in RAM.

Read Only Memory (ROM):

This memory uses Metal Oxide Semiconductor Technology. RAM is read-write memory whereas ROM is Read-Only-Memory. This memory is used to store frequently used programs in the system and also storing a special software called BIOS (Basic Input / Output System). This software helps to load the operating system when the computer is switched on.

Distinguish between RAM and ROM:

	RAM		ROM
1.	Random Access Memory.	1.	Read Only Memory.
2.	It is Volatile or temporary memory.	2.	It is Non-Volatile or permanent memory
3.	Data gets erased when power supply off	3.	Data stored permanently
4.	Faster memory.	4.	Slow memory.
5.	It is used in the normal operations of a computer after starting up and loading the operating system.	5.	A ROM chip is used primarily in the start-up process of a computer.

2. Secondary Memory or Auxiliary Memory:

This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently. CPU directly does not access these memories. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. Secondary storage devices that were used earlier are – floppy disks, zip discs and punched cards. The floppy disk is a removable magnetic storage medium. A normal 3½ inch disk can store 1.44 megabytes of data.

For example- Magnetic Disk, Hard Disk, Optical Disks, CD-ROM, DVD, etc.

Hard Disk

1. A hard disk is the main secondary-storage device found inside the CPU box.
2. It can store large amount of data.
3. All the work done on a computer can be stored on a hard disk.

CD (Compact Discs)

1. CD are circular in shape.
2. They can be easily carried from one place to another.
3. Most of the programs and games that you use on your computer are available on CDs.
4. They store up to 700MB of data.

CDs can be of two types

• CD-R - meaning CD-Recordable, they are cheap and work best when recording data that will not change.  In other words, once data has been written to the disc it cannot be erased again.
• CD-RW - meaning CD-Rewritable, where data once written to the disc can be erased and the disc written to over and over. CD-RW media can only be written to in a CD-RW drive.

DVD (Digital Versatile Disk)

1. A DVD looks like a CD.
2. A DVD is capable of storing six times more data than a CD.
3. A DVD can be single or double sided.
4. A single sided DVD can store up to 4.7 GB.
5. A double-sided DVD can store roughly 9.4GB of data

Blu-ray Disk (BD)

1. The name blue-ray disc is derived from the blue-violet laser that is used to read and write this type of disc.
2. A blue-ray disc can store five times more data than a DVD.
3. A BD can be single or double sided.
4. A single sided BD disc can store up to 25 GB.
5. A double-sided BD disk store 50 GB of data
6. It is mainly used for storing very high-quality video files and video games that require large amount of storage space.

Pen/ Flash Drive

1. Pen drive is a storage device which is very small in size.
2. It can be easily carried in a pocket.
3. It can be connected to the USB (Universal serial Bus) port of a computer.
4. They store from 4GB, 8GB, 16GB, 32GB to 256 GB and more.

Memory Card

1. It is storage device that is used for storing media and data files.
2. Memory cards are commonly used in small, portable devices, such as cameras and mobile phones, digital cameras, mp3 players and many others portable devices.

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