Network Model

 The term computer network model defines the category in which a computer network can be grouped into. Networks are divided into two broad categories:

1.Peer to peer or Workgroup Model

2.Domain based model or Client/server model

1.Peer to peer or Workgroup Model

When nodes or workstations perform the same communication functions, they are referred to as peers, in this network model, both server and client operations are performed by the same computer. Each user administers his/her workstation and the resources in it. In a peer-to-peer network, there are no dedicated servers, and there is no hierarchy among the computers. All the computers are equal and therefore are known as peers. Each computer functions as both a client and a server, and there is no administrator responsible for the entire network. The user on each computer determines which data on that computer is shared on the network.

Advantages of using peer to peer

• They are easy to configure
• Computers communicate easily.
• They don’t require additional server hardware or software
• Users can manage their own resources.
• They don’t require a network administrator
• They reduce total cost of network setup.

Disadvantages of using peer to peer

1. They provide a limited number of connections for shared resources.
2. Computers with shared resources suffer from sluggish performance.
3. They don’t allow for central management
4. Users are responsible for managing resources. These resources include data in shared directories, printers, fax cards, and so on.
5. They offer very poor security.

2.Domain based model or Client/server model

This is a network model that offers centralized access to services and devices. One computer plays the role of a server. It is the most common type of network architecture today that provides centralized data storage, security, manning of applications and network administration. Most servers operating system are Novel Netware, Windows NT, Apple talk, Linux, Banyan VINES etc…

Disadvantages

• Cost: – More expensive in terms of hardware and network operating system.
• Complexity: – Experienced system administrators are required to manage the systems.
• Dependence: – When server goes down, operations will cease across the network.

Advantages

1. They are best suited for 10 or more users.
2. Security: – All major server based systems provides sophisticated security.
3. Administration: – Servers are centralized making them easier to manage.
4. Stability: – Server based systems are designed to support a wide range of organization sizes. Additional servers are added to increase capacity.
5. Client server networks offer centralized backup where data can be stored in one server.
6. Flexibility – New technology can be easily integrated into the system.
7. Accessibility – Server can be accessed remotely and across multiple platforms.

Applications of Computer

 There are many applications of computers and which are used in various fields.

Below are the names of the fields where the applications of a computer are used.

• Education & Training centers
• Business
• Banking & Financial company
•  Entertainment
• Engineering
• Accounting
• Communications
• Digital Advertisement
• Pharmacy & Hospital
• Office
• Library
• Transporting
• Gaming
• CAD/CAM

Applications of Computer in Education

In the field of education too, the application of computer is being used to teach children in every school, college, the university today.

Through education applications, children are being taught in an even better way so that children are reading and understanding better. Through education applications, you can read and create digital books, digital notes. There are many applications of such education that run through the internet.

Today in every training center such as a computer training center, driving training center and many more training centers are being taught using training applications.

Applications of computer in Business

Computers are also being used in the field of business so that the business can be made more profitable and the business of businessman becomes even easier.

There are many business applications in the market today for business as well.

Through these business applications, you can completely monitor your business like - do calculations, give e-bill or paper bills to customers, do sales analyses, check price, check stock of an item, how much is left in stock now is.

Applications of computer in Banking & finance

Even in the banking sector, today all the work is being done in every bank with the use of a computer.

With the use of computers, the work of banks has become fast and convenient, due to which bank customers are also getting a lot of benefits.

Today every bank in the world is dependent on computers because every bank does its work from computers like - printing bank holder's passbook, opening new accounts, electronic fund transfers, e-banking, and many more. are done by computer. The basic work of a finance company is to give loans to its customers, before giving a loan, this company checks the credit score of that customer, after that, it decides whether to give a loan or not.

 Applications of Computer in Entertainment

Computers are also being used tightly in the field of entertainment.

Today, the computer is the only means of entertainment for people around the world, due to which people never get bored and the number of people who are being entertained by computers is increasing day by day. The VLC media player is an entertainment application and there are many other types of entertainment that are given below.

• YouTube
• Amazon Prime
• Netflix

These are all entertainment applications.

Applications of Computer in Engineering

Computers are also being widely used in the engineering sector.

Today the engineer is able to complete every one of his projects through the computer only.

Engineers used to make blueprints of their projects from sketches, which take them a lot of time, but today engineers make blueprints of their projects from computers, which saves them a lot of time.

For example, civil engineers design the map of a house, complex, mall with CAD (computer-aided design).

CAD (computer-aided design) is a 2D and 3D designing application.

Mechanical engineers also use designing applications to make model designs of vehicles.

 Applications of Computer in Communication

Even in the field of communication, people are able to communicate with each other only through computer applications.

Through communication application, whenever people want to talk, they can talk to anyone.

The specialty of these applications is that it delivers your message within a few seconds from which you send the message.

These communication applications will be used by almost all the people of the world.

Through these communication applications, you can communicate with text, voice, and video.

Human Brain vs Computer

 

Key Differences Between Brain and Computer

1. The brain can have 100 teraflops of memory with a density of 107 circuits per cm3 while computer memory has the 100 million megabytes with a density of 1014 bits per cm3. Memory in brain grows instantly just by connecting synaptic link whereas in a computer to scale the memory the chips need to be added.
2. Brain has the inbuilt backup system where the functioning pathways replace the damaged pathways. As against, backup systems are constructed manually in a computer.
3. The energy consumption in the brain is less than the computer.
4. To store information the brain uses electrochemical and electromagnetic form. Conversely, in a computer, the information is stored in the symbolic and numeric form.
5. In the brain, the information is transmitted with the help of chemicals to fire action potential in the neurons. On the contrary, the computer uses electrically coded signals to transmit the data.
6. The processing power of the brain is unlimited and provides online processing, but the brain processes information at slow speed because neurons are slow in action. In contrast, the processing power of computers is significant because of fast transistors.
7. The brain is self-organised while the computer is preprogrammed structure.

RISC Vs CISC

 

BASIS FOR COMPARISON	RISC	CISC
Emphasis on	Software	Hardware
Includes	Single clock	Multi-clock
Instruction-set size	Small	Large
Instruction formats	fixed (32-bit) format	Varying formats (16-64 bits each instruction).
Addressing modes used	Limited to 3-5	12-24
General purpose registers used	32-192	8-24
Memory inferences	Register to register	Memory to memory
Cache design	Split data cache and instruction cache.	Unified cache for instructions and data.
Clock rate	50-150 MHz	33-50 MHz
Cycles Per Instruction	Single cycle for all instructions and an average CPI < 1.5.	CPI between 2 and 15.
CPU Control	Hardwired without control memory.	Micro-coded using control memory (ROM).

 

Master Slave Flip Flop

Basically, this type of flip flop can be designed with two JK FFs by connecting in series. One of these FFs, one FF works as the master as well as other FF works as a slave. The connection of these FFs can be done like this, the master FF output can be connected to the inputs of the slave FF. Here slave FF’s outputs can be connected to the inputs of the master FF.

In this type of FF, an inverter is also used addition to two FFs. The inverter connection can be done in such a way that where the inverted CLK pulse can be connected to the slave FF. In other terms, if CLK pulse is 0 for a master FF, then CLK pulse will be 1 for a slave FF. Similarly, when CLK pulse is 1 for master FF, then CLK pulse will be 0 for slave FF.

 

Master-Slave FF Working

Whenever the CLK pulse goes to high which means 1, then the slave can be separated; the inputs like J & K may change the condition of the system.

The slave FF can be is detached until the CLK pulse goes to low which means to 0. Whenever the CLK pulse goes back to low-state, then the data can be transmitted from the master FF to the slave FF and finally, the o/p can be obtained.

At first, the master FF will be triggered at a positive level whereas the slave FF will be triggered at a negative level. Due to this reason, the master FF responds first.

If J=0 & K=1, then the output of the master FF ‘Q’ goes to the input K of the slave FF & the CLK forces the slave FF to RST (reset), therefore the slave FF copies the master FF.

If J=1 & K=0, then the of the master FF ‘Q’ goes to the input J of the slave FF & the CLK’s negative transition sets the slave FF, and copies the master.

If J=1 & K=1, then it toggles over the CLK’s positive transition & therefore the slave toggles over the CLK’s negative transition.

If both the J & K are 0, then the FF can be immobilized & Q remains unmovable.

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SCANNERS

A scanner is a device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display. Scanners come in hand-held, feed-in, and flatbed types and for scanning black-and-white only, or color. 

 

HOW SCANNERS WORK
Scanners operate by shining light at the object or document being digitized and directing the reflected light (usually through a series of mirrors and lenses) onto a photosensitive element. In most scanners, the sensing medium is an electronic, light-sensing integrated circuit known as a charged coupled device (CCD). Light-sensitive photosites arrayed along the CCD convert levels of brightness into electronic signals that are then processed into a digital image.

A scanner consists of a flat transparent glass bed under which the CCD sensors, lamp, lenses, filters and also mirrors are fixed. The document has to be placed on the glass bed. There will also be a cover to close the scanner. This cover may either be white or black in colour. This colour helps in providing uniformity in the background. This uniformity will help the scanner software to determine the size of the document to be scanned.

The lamp brightens up the text to be scanned. Most scanners use a cold cathode fluorescent lamp (CCFL).

A stepper motor under the scanner moves the scanner head from one end to the other. The movement will be slow and is controlled by a belt. The scanner head consists of the mirrors, lens, CCD sensors and also the filter. The scan head moves parallel to the glass bed and that too in a constant path. As deviation may occur in its motion, a stabilizer bar will be provided to compromise it. The scan head moves from one end of the machine to the other. When it has reached the other end the scanning of the document has been completed. For some scanners, a two way scan is used in which the scan head has to reach its original position to ensure a complete scan.

As the scan head moves under the glass bed, the light from the lamp hits the document and is reflected back with the help of mirrors angled to one another. According to the design of the device there may be either 2-way mirrors or 3-way mirrors. The mirrors will be angled in such a way that the reflected image will be hitting a smaller surface. In the end, the image will reach a lens which passes it through a filter and causes the image to be focussed on CCD sensors. The CCD sensors convert the light to electrical signals according to its intensity. Take a look at the diagram given below.

The electrical signals will be converted into image format inside a computer. This reception may also differ according to the variation in the lens and filter design. A method called three pass scanning is commonly used in which each movement of the scan head from one end to another uses each composite colour to be passed between the lens and the CCD sensors. After the three composite colours are scanned, the scanner software assembles the three filtered images into one single -colour image.

Digitizer, stylus, Accelerometer and Gyroscope

 

A digitizer is a hardware device that receives analog information, such as sound or light, and records it digitally. Usually, the information is stored in a file on a computing device. This process is called digitization.

For example, a digital camera is a digitizer. Light enters through the camera lens, and the hardware and software inside the camera converts that information to binary data, and stores it an image file. The user may then transfer the file to a computer, where he or she can edit the image, print it out, or share it online.

Examples of digitizers

A digital camera is one example of a digitizer. Other examples include:

Audio digitizer

Most computers have a microphone jack, where you can connect an analog microphone. The analog input (the audio signal) is processed in the computer by a discrete sound card, or by audio hardware on the motherboard itself. This data can then be used by software running on the computer. Some audio digitizers are small hand-held devices, and some are expensive peripherals that provide professional-level conversion quality. The microphone in a smartphone is another audio digitizer.

Digital Tablet

A tablet is a computing device that is controlled with a finger or a digital pen called a stylus. A tablet is usually larger than a smartphone, but smaller than a computer monitor. Some tablets have a screen, which is touched directly, and some tablets are peripheral devices, without screens, which attach to a computer. The user can write, draw, and paint by touching the tablet. Software converts the analog touch input to lines or pressure-sensitive brush strokes in a document. The software may also perform handwriting recognition to convert handwritten text to typewritten words. When dealing with graphics these tablets are often referred to as a graphics tablet.

Accelerometer and gyroscope

Digitizers inside smartphones and tablet computers can detect how fast the device is moving (an accelerometer), and the angle it's held (a gyroscope). The analog information of motion and angular rotation is converted to data your apps can use in real time. For example, using a gyroscope, a smartphone could be held up to the sky to receive information about the position of stars and planets. The accelerometer helps reduce motion blur when you're taking a photo, and can trigger safety mechanisms if the device is accidentally dropped.

 

MAC Address

 A MAC (Media Access Control) address is a 48 bit unique ID assigned to every internet-connected machine that allows it to be identified when connected to a specific network. Also known as Hardware Address or physical address of machine on network.

A MAC address is a hardware identification number that uniquely identifies each device on a network. The MAC address is manufactured into every network card, such as an Ethernet card or Wi-Fi card, and therefore cannot be changed. 

MAC is divided into The vendor ID (24 bit) and other NIC identifier 24 bit.

Because there are millions of networkable devices in existence, and each device needs to have a unique MAC address, there must be a very wide range of possible addresses. For this reason, MAC addresses are made up of six two-digit hexadecimal numbers, separated by colons. For example, an Ethernet card may have a MAC address of 00:0d:83:b1:c0:8e. Fortunately, you do not need to know this address, since it is automatically recognized by most networks.

Finding Your MAC Address

windows

1. Click Start then Run (in Windows 7, Start and type in the Search Programs and Files box.)
2. Enter: cmd
3. Enter: ipconfig /all
   If the output scrolls off your screen, and it will on Vista and Windows 7, use: ipconfig /all | more
4. The Physical Address is your MAC address; it will look like 00-15-E9-2B-99-3C. You will have a physical address for each network connection that you have.

 Linux

Linux

1. Become root, using su.
2. Enter: ifconfig -a

   # ifconfig -a
   eth0      Link encap:Ethernet  HWaddr 00:09:3D:12:33:33  
             inet addr:10.248.155.17  Bcast:10.248.255.255  Mask:255.255.0.0
             inet6 addr: fe50::234:3dff:fe12:7d73/64 Scope:Link
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:3489041718 errors:0 dropped:0 overruns:0 frame:0
             TX packets:3259212142 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:1000 
             RX bytes:2732221481 (2.5 GiB)  TX bytes:4065716672 (3.7 GiB)
             Interrupt:185

3. The ethernet devices are called eth0, eth1, and so on The MAC address is in the first line of the output, labeled HWaddr, it is 00:09:3D:12:33:33.

 

 

 

UNIX -- An INTRODUCTION

 

What Is UNIX?

UNIX is an operating system developed in the Bell Laboratories AT&T and is an example a multi-tasking, multi-user operating system. It provides its users with: program development tools; electronic communications facilities, such as an electronic mail; text editors and text formatters. There are also many development tools available as standard within the UNIX operating system that other operating systems require as add-ons.

UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.

UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.

Types of UNIX

There are many different versions of UNIX, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X.

Operating System Notes Part 2 PDF

OS NOTES PART 5

OS NOTES PART 6

OS NOTES PART 7

OS NOTES PART 8

OS NOTES PART 9

OS NOTES PART 10 

 

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