Explain different types of storage devices

Topic: Explain different types of storage devices in Computer systems

Storage Devices

Storage devices are used to store data and instructions permanently. Storage devices are also called secondary storage devices / backing storage devices / external storage devices or auxiliary storage devices. Examples of storage devices include Hard Disk, CD and DVD etc.

Why Secondary Storage Devices are Used?

Secondary storage devices are used because:

1. Primary memory(RAM) is volatile and temporary. When computer is switched off, all data in ram is erased.
2. Storage devices can store large amounts of data and instructions permanently whereas Primary memory has less capacity of storing data.

Types Of Storage Devices

There are three main types of storage devices:

•  Magnetic Tape 
•  Magnetic Disk 
•  Optical Disk 
•  Flash Memory storage devices

1. Magnetic Tape



Magnetic tape is the oldest storage device. It is made of plastic coated with magnetic material. Data is stored on magnetic tape in the form of magnetic spots. Tape drive is used to read and write data on tape. Magnetic disk is sequential access device. It is slower device than magnetic disk or optical disk. Magnetic tapes are used in reels of different lengths, for example 200, 600, 1200 feet etc.

2. Magnetic Disk

A magnetic disk is a thin circular metal or plastic disk coated with magnetic material. Data is stored in the form of magnetic spots. Magnetic disk is random access device. It is faster than magnetic tape. There are three main types of magnetic disk:
a. Hard Disk b. Floppy Disk c. Zip Disk

a. Hard Disk

The hard disk is also called fixed disk. It consists of one or more metal plates. The plates are fixed in the drive. Metal plates are coated with magnetic material to store data. A motor rotates disks. There is also an access arm and read / write heads to read and write data on disks.
Following are major characteristics of hard disk:
- The storage capacity of hard disk is much greater than floppy disk.
- Now a days hard disks of size 40 GB, 80 GB or more are available.
- Hard disk is covered in a hard jacket and there are less chances of disk damage due to dust and mishandling.
- Now days Operating system and application programs are installed on hard disk.
- Before using a magnetic disk we use operating system to format the disk. Operating system divides the disk into circles called tracks. Each track is divided into pie-shaped areas called sectors. Data is stored in sectors. Each sector can store 512 bytes.

b. Floppy Disk

Floppy disk is a small plastic plate coated with magnetic material. Data is stored in magnetic spots. Main advantage of floppy disk is that it is used to transfer data from one computer to another. Floppy disk drive is used to read and write data on floppy disk.
Floppy disk is available in two sizes:
· 3 ½ INCH Floppy Disk
It is also called micro floppy disk. Its diameter is 3½ inch. It is covered in a hard plastic cover. Read/Write window is covered with a metal shutter. When disk is inserted into disk drive then shutter is automatically opened. It can be write protected by a notch. Storage capacity of micro floppy is 1.44 MB.
· 5¼ Inch floppy disk.
It is a 5¼ inch diameter plastic plate coated with magnetic material. Its storage capacity is 1.2 MB. It is not used in modern computers.

c. Zip Disk

Zip disk is similar to 3 ½ inch floppy disk. But it can store 100 MB or more data. Zip disk drive is used to read and write data on a zip disk.

3. Optical Disk

LASER technology is used to read and write data on Optical disk. LASER stands for Light Amplification through Emission of Radiation. Laser beam writes on the surface of optical disk by creating very small holes. The presence of hole represents a One and absence of the hole represents a Zero. There are following main types of optical disk.
1.CD-ROM, 2. CD-R or WORM, 3. CD-RW
4.DVD-ROM, 5. DVD-R, 6. DVD-RW, 7. Blue-Ray disk

 1. CD-ROM



CD-ROM stands for Compact Disk-Read Only Memory. The data stored on Cd-Rom can only be read. It cannot be deleted or changed. It is a portable storage device. Data can be easily transferred by CD Rom from one computer to another. Commonly it can store 650 MB / 700 MB/ 750 MB data. It is used to store large amounts of data like Software or audio/video data.We purchase Software, movies, dramas, lectures, books, wallpapers and other data on Cd-Rom. There are many Advantages of Compact Disk.

2. CD-R (CD Recordable) Or WORM (Write Once Read Many)

CD-R stands for Compact Disk -Recordable. Initially, it is a blank disk. User can store data on it only once. This is why it is also called WORM(Write Once Read Many) disk too. Because we can write data on it only once and later we can read many times. The devices to store data on CD-R are called CD Writers or CD Burners. We can write data on CD-R only once, but can read data many times. Because of this write once read many quality, CD-R is often known as WORM(write once read many).

3. CD-RW ( CD Rewritable )

CD-RW stands for Compact Disk Rewritable. This is a special type of CD. User can write data on it, if there is an error in writing data, he may erase the contents and rewrite again. CD-Writers are used to store data on CD-RW.

4. DVD - Digital Video Disk (DVD-ROM)

DVD stands for Digital Video Disk. A laser beam with a short wave length is used to create very very small holes on the surface of disk. So there are much more tiny holes on the surface of DVD as compared to that of CD. Therefore, storage capacity of DVD is much larger than CD. It can store up to 17 GB or more data. DVD-ROM is pre recorded and it can contain data like movies, videos and software etc. User cannot change or delete data from DVD-ROM. It is read only. There are several Benefits of using Digital Video Disk or DVD.

5. DVD-R (DVD-Recordable)

DVD-R stands for Digital Video Disk Recordable. Initially it is a blank disk. User can store data on disk only once. Then it becomes read only. It is normally used to store high definition video movies. DVD-Writers are used to store data on DVD-R.

6. DVD-RW ( DVD Rewritable)

DVD-RW stands for Digital Video Disk Rewritable. User can write data on disk many times by erasing the old data.

Blu-Ray Disk

Blu-Ray Disk is an optical disk used to store digital information such as high-definition video, and able to store more information than a standard DVD
Blu-ray Disk pronounced as Blue-ray Disk is the name of a new type of optical disc
format. The format offers more than five times the storage capacity of traditional DVDs. A Blu Ray disk can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc.

Moreover an other difference between DVD and Blu-Ray disk is that current optical disc technologies such as DVDs rely on a red laser to read and write data, whereas the new format ( Blu-Ray disk) uses a blue-violet laser instead, hence the name Blu-ray Disk.

Blu-ray disk

Here are some Differences Between CD and DVD.

4. Flash Memory Storage Devices

Flash memory is a non volatile memory - a kind of memory that retains data in the absence of a power supply. We can write new data on flash memory devices and can erase the existing data electronically.
Flash memory devices contain no moving parts.

Different types of flash memory storage devices are as follows:

Solid State Drives
USB Flash Drives
Memory Cards




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Discuss Differences Between RAM and ROM

We have already discussed the topics:
1. What is RAM, Explain Different Types of RAM
2. What is ROM Explain Different Types of ROM
Here we discuss differences between RAM and ROM

13 Differences Between RAM and ROM

Thirteen Differences Between RAM and ROM

Sr #	RAM	ROM
1	RAM stands for Random Access Memory	ROM stands for Read Only Memory.
2	RAM is a temporary memory.	ROM is a permanent memory.
3	RAM is a volatile memory.	ROM is a non volatile memory.
4	When computer is turned off, all data and programs are erased from RAM.	When computer is turned off, all data and programs are retained in ROM.
5	RAM is a Read / Write memory. Data can be read and written to RAM.	ROM is a read only memory. Data from ROM only can be read and not written.
6	Data and programs in RAM can be changed.	The contents of ROM cannot be changed.
7	Data or programs in RAM can be deleted.	Contents of ROM cannot be deleted.
8	The instructions and data  are written (loaded) in RAM at execution time, when computer is working.	The instructions in ROM are written at the time of manufacturing.
9	RAM is used to load data and programs currently running.	ROM contains the instructions that help the computer to start-up and make it ready for work.
10	RAM is much faster than ROM.	ROM is slower than RAM.
11	RAM has two main types: Static RAM and Dynamic RAM	ROM has three types: PROM, EPROM and EEPROM
12	Physically RAM chip is larger than ROM chip.	Physically ROM chip is smaller than RAM chip.
13	Picture of RAM is: RAM	Picture of ROM is: ROM

These were the differences between Random Access Memory and Read Only Memory

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What is ROM Explain Different Types of ROM

Topic: What is ROM Explain Different Types of ROM

ROM

ROM stands for Read Only Memory, because its contents can be read and used only and we cannot change or delete its contents. It is a non volatile memory. Its retains its contents even after switching off the computer. Therefore, ROM does not require electricity to retain its contents. ROM is a permanent memory. The instructions in ROM are written at the time of manufacturing by the manufacturer.  

Importance of ROM in Computer System

1. One important reason a computer needs ROM is that instructions stored in ROM (called ROM BIOS - Basic Input/Output System)execute on start-up of computer and guide the computer what to do. They make the computer ready for work.
2. ROM contains a set of start-up instructions to check that memory is functioning well and check for other hardware devices.
3. These instructions also check for an operating system and load its necessary part into RAM, so that a user interface for example "Windows Desktop" is displayed on computer screen. Now computer is ready to work with. A user now can easily perform work on computer.

Where ROM Chip is installed in Computer?

ROM chip is fixed on motherboard as shown in the figure: AMIBIOS -American Megatrends ROM chip.

Another picture of Rom

Types of ROM

Following are the types of ROM

• PROM

PROM stands for Programmable Read Only Memory. Instructions can be stored in PROM only once. Then it becomes ROM and we cannot change instructions in it. Initially PROM is a blank chip. Once instructions are written on it, then it become ROM. Now we cannot change or delete the instructions. If there is any error in writing instructions then PROM chip becomes unusable.

• EPROM

EPROM stands for Erasable Programmable Read Only Memory. Program instructions written on EPROM can be erased and changed with the help of ultra violet rays. So if once we write instruction on this chip with errors, we can erase wrong instructions and rewrite new instructions.

• EEPROM

EPROM stands for Electrically Erasable Programmable Read Only Memory. Program instructions written on EEPROM can be erased with the help of electricity and rewritten.

Computer Hardware Concepts

2.1 What are Different Types of Hardware
2.2 What are Different Types of Input Devices
2.3 Explain Different Types Of Output Devices
2.4 Explain Parts of CPU and its Working
2.5 What are Dual Devices or Both Input/ Output Devices
2.6 What is RAM, Explain Different Types of RAM
2.7 What is ROM Explain Different Types of ROM
2.8 Discuss Differences Between RAM and ROM
2.9 Explain different types of storage devices
2.10 What are Pointing Input Devices
2.11 Different Types of Mouse Input Device
2.12 Types Of Scanners Input Device

What is RAM, Explain Different Types of RAM

Today we are going to discuss Different Types of RAM, that is, Random Access Memory.

RAM    /    What does RAM mean

Ram stands for Random Access Memory. Data in RAM can be accessed directly. That is, we can access data directly from any location of RAM in the same time. This Random Access quality makes RAM a very fast memory. RAM is volatile. Data and programs in RAM are erased when computer is turned off.

What does RAM do

Therefore RAM is a temporary memory. It is used to store those data and programs, which are currently being executed by CPU. Ram is also called Primary Memory or Main Memory.

Where RAM memory chip is installed?

RAM chip is installed into one of the memory slots on motherboard, as shown in the figure:

What does RAM mean

Importance of RAM.

1.  A Program must be laoded in RAM for execution.
The programs and data currently being executed are in computer's main memory, that is, in RAM. The programs and data needed by these programs is loaded into RAM and run from this memory for FAST ACCESS. Because hard disk is very slow device, every program we run, is loaded into RAM from hard disk first, and then it is executed by processor. CPU is very fast device, it can take instructions and data to execute from RAM much faster than from a hard disk. 


2. RAM is an  Important Factor in increasing Speed of Computer

One of the most important factors affecting the speed and power of a computer is the AMOUNT OF RAM it has. Normally, the more RAM a computer has, the more speed and power of working it has.In fact,  if a computer with a very fast processor has inadequate amount of RAM, it may still run slowly, especially when running multiple programs.

Discuss Different Types of RAM Random Access Memory/ what are the types of  RAM

Types of Ram

What are the types of  Ram

There are two main types of Ram.

• Dynamic Ram (DRAM)

Dynamic Ram is widely used in personal computers. It is a cheaper kind of RAM. DRAM stores data in the form of an electric charge. DRAM loses electric charge with the passage of time, so DRAM needs to be refreshed frequently. Otherwise, it may lose data. Dram is recharged many times in a second. Therefore, it is slower than SRAM. Since CPU cannot access the data from DRAM while it is in the process of refreshing or recharging.

• Static Ram (SRAM)

Static Ram does not need to be refreshed again and again. So processor can access data from static RAM faster than DRAM. There is no time wastage in refreshing the memory again and again. Static RAM is more expensive and faster than DRAM. Static Ram is used to build a very fast memory called CACHE (pronounces 'cash' ) memory.

Computer Hardware Concepts

2.1 What are Different Types of Hardware
2.2 What are Different Types of Input Devices
2.3 Explain Different Types Of Output Devices
2.4 Explain Parts of CPU and its Working
2.5 What are Dual Devices or Both Input/ Output Devices
2.6 What is RAM, Explain Different Types of RAM
2.7 What is ROM Explain Different Types of ROM
2.8 Discuss Differences Between RAM and ROM
2.9 Explain different types of storage devices
2.10 What are Pointing Input Devices
2.11 Different Types of Mouse Input Device
2.12 Types Of Scanners Input Device

What are Dual Devices or Both Input/ Output Devices

The devices that can be used to perform both functions -input and output- are called Dual Devices. These devices are also called Dual Purpose Devices or Both Input/Output Devices. With the help of a dual purpose device, we can enter data into computer as well as we can output data from the computer to outside world.  For example, Dual devices include:  Touch Screen Monitor, Modem, Network Interface Card, Sound card, Hard disk drive, Floppy disk Drive, Magnetic Tape Drive CD-Writer and DVD-Writer etc. These are also called Input/output devices, because they perform both functions.

• Touch Screen Monitor

Dual Devices or Both Input / Output Devices - Touch screens

Touch Screen Monitor is an input/output device. It uses a special touch sensitive screen. The User can enter data by touching icons or menus on the screen. As soon as the user selects a command from menu, output is displayed on screen. Commonly touch screen monitors use sensors to detect touch of finger.

•      Headset

A headset may be considered as both Input / Output device, because it has a microphone for voice input and small speaker phones for  sound output.

Example of Both Input / Output Devices - headsets

Headsets are used for video conferences and video calls through SKYPE and other such free software to make video calls.

• Modem

Internal modem

External modem

Modem stands for Modulator / Demodulator. Modem is a communication device.  It makes possible receiving data from internet into our computer (input) and sending data from our computer to another computer on internet(output).  It performs two functions: Modulation (converting digital signal into analog signal) and Demodulation(converting analog signal to digital signal). It makes possible receiving data from internet into our computer (input) and sending data from our computer to another computer on internet(output). Modem sends and receives data from one computer to another through telephone lines. It links your personal computer to the Internet through your ISP (Internet Service Provider). A telephone line supports only analog signals, whereas computer accepts only digital signals. So when a computer wants to send data to another computer, digital data is converted into analog data before placing on telephone line. The process of converting digital signal into analog signal is called Modulation. Similarly, on the receiving computer, modem converts analog data (from telephone line) into digital data, before it is entered into receiving computer. The process of converting analog signal into digital signal is called Demodulation.

• NIC - Network Interface Card

NIC or LAN card - NIC is Example of Dual devices

NIC stands for Network Interface Card. It is used to link network computers for transmitting data. With the help of NIC our computer can receive  data, instructions and information from another computer (input). NIC will also be helpful to send data from our computer to another computer on the network (output). NIC is also called a LAN card, local area network card or LAN adapter.

• Sound Card

Sound card or audio card

A sound card is a computer component that facilitates the input and output of audio signals to and from a computer. A speaker produces audio output with the help of sound card. In addition we use microphone to input our voice into computer with the help of sound card. 

•     Hard disk Drive

Hard disk drive is an input/output device. It has read/write heads to read data from hard disk(input) and to write data to hard disk(output).

• Floppy disk Drive

Floppy disk drive is an input/output device. It has read/write heads to read data from floppy disk(input) and to write data to floppy disk(output).   

• Magnetic Tape Drive

Magnetic Tape drive is an input/output device. It has read/write heads to read data from magnetic tape(input) and to write data to magnetic tape(output).

• CD-Writer / CD-Recorder

CD-Writer is an input/output device. It is used to store data on CD. It is used to read data from CD(input) and to write data to CD(output).

• DVD-Writer / DVD-Recorder

DVD-Writer is an input/output device. It is used to store data on DVD. It is used to read data from DVD(input) and to write data to DVD(output).

Computer Hardware Concepts

2.1 What are Different Types of Hardware
2.2 What are Different Types of Input Devices
2.3 Explain Different Types Of Output Devices
2.4 Explain Parts of CPU and its Working
2.5 What are Dual Devices or Both Input/ Output Devices
2.6 What is RAM, Explain Different Types of RAM
2.7 What is ROM Explain Different Types of ROM
2.8 Discuss Differences Between RAM and ROM
2.9 Explain different types of storage devices
2.10 What are Pointing Input Devices
2.11 Different Types of Mouse Input Device
2.12 Types Of Scanners Input Device

Explain Parts of CPU and its Working

CENTRAL PROCESSING UNIT / CPU / Microprocessor / Processor

Central processing unit is the brain of computer. It is also called CPU or processor. Processor is used to process data according to given instructions. It performs arithmetic and logical operations on data.

Parts / Components of CPU / Processor on computergap.com

It controls all activities of different parts of a computer. As brain in human body controls all other parts of body and takes decisions, CPU controls all other parts of the computer and their working. A CPU has three basic parts: Arithmetic Logic unit, Control unit and Registers.

Parts of Microprocessor or Processor or CPU or Central Processing Unit computergap.com

1.    ARITHMETIC LOGIC UNIT (ALU)

ALU performs data processing according to given instructions. All computations are done in this unit. ALU is the real place in computer where actual execution of instructions takes place. ALU may be further categorized into two sections according to their function:
ARITHMETIC SECTION of ALU performs arithmetic operations like addition, subtraction, multiplication and division on data.
LOGIC SECTION of ALU performs logical operations like comparison between two values. For example, 10>5 will give TRUE answer. And 5<1 will give FALSE answer. Control unit sends data and instruction to perform calculation on the data to the ALU. ALU then performs this calculation. 

2.    CONTROL UNIT

Control unit controls all over operations of different parts of computer. For example it takes data and instructions from input unit and stores it into memory. It sends data to ALU for processing. It takes results from ALU and sends it to output device. It can also store results in memory. Control unit performs all these functions by giving commands to relevant part of the computer.
Control unit performs following four functions for executing instructions of a computer program.

1.  Fetching: obtaining instruction from memory
2.  Decoding: understanding this instruction
3.  Data Fetching: If needed, obtaining data from memory
4.  Executing: Control unit sends the instruction and data to ALU for taking suitable action on the instruction

3.    REGISTERS

A register is a very small and temporary memory area in ALU. It holds instruction and data as long as it is being processed by CPU. When instruction and data is fetched from memory then it is stored in a register. ALU contains a number of registers for example AX, BX, CX, DX etc. A Register may be of 8 bits, 16 bits, 32 bits or more.

Computer Hardware Concepts

2.1 What are Different Types of Hardware
2.2 What are Different Types of Input Devices
2.3 Explain Different Types Of Output Devices
2.4 Explain Parts of CPU and its Working
2.5 What are Dual Devices or Both Input/ Output Devices
2.6 What is RAM, Explain Different Types of RAM
2.7 What is ROM Explain Different Types of ROM
2.8 Discuss Differences Between RAM and ROM
2.9 Explain different types of storage devices
2.10 What are Pointing Input Devices
2.11 Different Types of Mouse Input Device
2.12 Types Of Scanners Input Device

Explain Different Types Of Output Devices

Output devices


Out put devices are used to display results of processing to the user. They perform the following functions:

1.  Receive results from memory
2.  Convert data into human readable form
3.  Display results to the user

Examples include: Monitor, printer, plotter, speaker, and multimedia projector.

Different Types of Output Devices

1.    Monitor

LCD Monitor

CTR Monitor

   

Monitor is the most commonly used output device used to display results of processing. It has a TV like shape. Pictures on monitor are formed with picture elements called PIXEL. Monitors may be Monochrome that will display results in Black & White. Color Monitors are also available. They display results in multi colors. Monitor produces soft copy output.


2.    Printers

Printers are used to produce hard copy out put. They print processing results on paper. Printers are divided into two main categories:
·    Impact Printers
·    Non Impact printers

Impact Printers.

These printers print with striking of hammers or pins on ribbon. For example Dot Matrix printer and daisy wheel printers are impact printers.

Non-Impact Printers.

These printers do not use striking mechanism for printing. They use electrostatic and laser technology. Quality and speed of these printers is better than Impact printers. For example Laser printer and Inkjet printers are non-impact printers.

3.    Speaker and Headsets

Speakers for Desktop computer

Speakers and head sets produce sound output. We can listen recorded voices, sounds or music with the help of speaker or headset. Speaker produces sound output with the help of sound card.

Headsets - used to produce audio output

4.    Plotter

A plotter is an output device used to produce image-quality graphics in a variety of colors. Plotters are used to print large maps, architectural drawings, graphs and charts. Plotters are used to draw different designs of buildings or internal structure of machines. Plotters offer the fastest way to efficiently produce very large drawings or color high-resolution graphics. Engineers and Architects use plotters.

5.    Multimedia Projector.

Multimedia Projector

Multimedia projector is used to produce computer output on a big screen. These are used in meeting rooms or in classrooms of educational institutes. Since the output produced by multimedia projector is displayed on a large screen, it can be viewed by a large number of people in a hall, meeting / conference room or a class room. Mostly teachers use data projectors in class rooms for delivering lectures ( a use of audio visual aids technology)

Computer Hardware Concepts

2.1 What are Different Types of Hardware
2.2 What are Different Types of Input Devices
2.3 Explain Different Types Of Output Devices
2.4 Explain Parts of CPU and its Working
2.5 What are Dual Devices or Both Input/ Output Devices
2.6 What is RAM, Explain Different Types of RAM
2.7 What is ROM Explain Different Types of ROM
2.8 Discuss Differences Between RAM and ROM
2.9 Explain different types of storage devices
2.10 What are Pointing Input Devices
2.11 Different Types of Mouse Input Device
2.12 Types Of Scanners Input Device