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Pin Diagram Of 8086 Microprocessor: The Hardware Model

The 8086 is a 16-bit microprocessor intended to be used as the CPU in a microcomputer. The 8086 Microprocessor - Internal Architecture sh...

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Hexadecimal Number System


Hexadecimal or base 16 number systems having 16 possible symbols, the decimal symbols 0 through 9 are used up and the letters A through F for values 10 through 15. This number system is often called Hex code.

Conversion from Binary to Octal and Octal to Binary

The conversion from Binary to Octal Numbers are quite simple. Steps are as follows.

Octal Number System and Conversions

A octal or base 8 number systems having 8 symbols 0 through 7.  The number system is as like 0, 1, 2, ….., 6, 7, 10, 11, 12,……, 16, 17, 20, 21, 22  and so on.

Transmission Media (Guided): Coaxial Cable

Baseband Coaxial Cable:

Another Common transmission medium is the coaxial cable. It has better shielding than twisted pairs. It consists of a stiff copper wire surrounded by an insulating material.
The insulator is encased by a braided mesh cylindrical conductor. The outer conductor is covered in a protective plastic sheath.
Coaxial cable gives a good combination of high bandwidth and excellent noise immunity. The bandwidth is depends on cable length. E.g. 1-km cables, data rate of 1 to 2 Gbps.
This cable is commonly used in telephone system, cable television and some LAN.
Coaxial cable is commonly used in two types. 50-ohm cable, called baseband coaxial cable, is commonly used for digital transmission.
Another 75-ohm cable, called broadband coaxial cable, is commonly used for analog transmission on standard cable television cabling.

A Coaxial Cable

Broadband Coaxial Cable:

Broadband networks (a) Dual cable, (b) Single cable.
Broadband systems typically cover a large area and therefore need analog amplifiers to strengthen the signal. These amplifiers can only transmit signals in one direction, so a computer outputting a packet will not be able to reach computers upstream from it if an amplifier lies between them. To solve this problem, two types of broadband systems have been developed: Dual cable and single cable systems.
Dual cable systems have two identical cables running in parallel. The root of the cable tree is head-end. All computers transmit data on cable 1 and receive data on cable 2.
The single cable system allocates different frequency bands for inbound and outbound communication on a single cable. The low frequency band is used for communication from the computers to the head-end, which then shifts the signal to the high-frequency band and rebroadcast it. for inbound traffic, 5 to 30 MHz frequencies are used, and for outbound traffic, 40 to 300 MHz frequencies are used.


Fiber Optics: The Transmission Media

An optical transmission system has three components: the light source, the transmission medium, and the detector. The transmission medium is an ultra-thin fiber of glass. The detector generates an electrical pulse when light falls on it.

Transmission Media (Guided): Twisted pair:

A twisted pair consists of two insulated copper wire about 1mm thick. The wires are twisted in a helical form to reduce the electrical interference from similar pairs. Twisted pairs can be used either analog or digital transmission. The bandwidth depends on the thickness of the wire and the distance traveled, but several megabits/sec can be achieved for few kilometers.

The Unguided Transmission (Wireless): Light wave Transmission

A modern application is to connect the LANs in two buildings via lasers mounted on their rooftops. So each building needs its own laser and its own photo detector.

The Unguided Transmission (Wireless): Infrared and Millimeter Waves

Infrared and millimeter waves are widely used for short-range communication. The remote controls used on televisions, VCR’s, and stereos all use infrared communication.

They are relatively directional, cheap, and easy to build, but they cannot pass through solid objects.
It can be used for indoor wireless LANs; without any interfere with a similar system in adjacent rooms i.e. security is better than radio systems.  
It cannot be used outdoors because the sun shines as brightly in the infrared as in the visible spectrum.

The Unguided Transmission (Wireless): Microwave Transmission

Microwave communication is widely used for long-distance telephone communication, cellular telephones, television distribution, and other uses, that a severe shortage of spectrum has developed.

The Unguided Transmission (Wireless): Radio Transmission

Radio Transmission
Radio waves are easy to generate, can travel long distances, and penetrate buildings easily, so they are widely used for indoor and outdoor communication.
Radio waves also are omnidirectional, means they can travel in all directions from the source. The radio waves are frequency dependent, at low frequencies radio waves pass through obstacles well, such as VLF, LF, MF bands; radio waves follow the ground, as shown in fig.

Binary Number System

Binary Number System: A binary or base 2 number systems having 2 symbols 0 and 1s.

The number system is as like 0, 1, 10, 11, 100, 101, 110, 111, 1000 etc. By adding 1 to last number i.e. 1 + 1 = 10, again 10 is a combination of existing 0 and 1 digit only.

Number Systems: Decimal Number System

Decimal Number System: A Decimal Number systems means group of 10 numbers (based on the number 10) from 0 through 9.

The next number is formed by adding 1 to last number i.e. 9 + 1 = 10, again 10 is a combination of existing 0 to 9 numbers. When we write numbers, the position (or "place") of each number is important. The digits in the decimal number 5346 tell you that you have 5 thousands, 3 hundreds, 4 tens, 6 ones. This number system contains decimal point. E. g. 5346.7, 5 thousand, 3 hundred, 4 tens, 6 ones and 7 tenths
  5    3    4     6     .  7   

                                               103 102 101  100    10-1

Types of Programming Languages:

The computer programs that run on a computer are called software.  Programmers write the instructions in various programming languages,

but computer can understand only one language called machine language and other languages that may require Intermediate translator to perform the conversion. The so many computer languages are use today and these languages may be divided into three category.

Computer Definition

Introduction

Computers today have gained access to every aspects of our life. Computers appear to us in so many ways that many times we fail see them as they actually are. Business today relies on computer technology to assist them in almost every area of corporate life. It is hard to imagine a world without computers. Computers are changing the way people work and communicate, they are become more and more a part of our everyday lives.

What is Computer?

A computer is an electronic device that accepts input, processes data, stores data and produces output, all according to a series of stored instructions (program).

A computer is an electronic device that process raw data and generates meaningful information under the control of set of instructions with speed and accuracy.

The 4 basic operations are:

      i.          Input: entering data into the computer.

    ii.          Processing: performing operations on the data.

  iii.          Output: presenting the results.

  iv.          Storage: saving data, programs/output for future use

Computer System=Hardware + software + User

Where, Hardware=Internal Devices + Peripheral Devices

             Software=Programs

             User=Person who operates computer.

Hardware: The term Hardware refers to the Physical components of computer such as mouse, keyboard, monitor etc.

Software: Software refers to the instructions or programs that make the computer work.  Example: word, excel, e-mail, notepad etc.

Program: A program consists of step by step instructions that tell the computer how to do its work. The purpose of software is to convert data into Information.

Computers are very powerful & cheap enough to do tasks such as video conferencing, image processing, animations, speech processing etc.

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The Unguided Transmission (Wireless): The Electromagnetic Spectrum

In guided media, medium is more important in setting transmission parameters, whereas in unguided media, signal characteristics is more important.

Wireless transmission medium typically used where laying a cable is not practical. For example
If running a fiber (or any guided medium) to a building is difficult due to the Terrain (mountains, jungles, swamps etc.)

Comparison of Fiber Optics and Copper Wire (Pros and Cons)

The comparison of fiber optics cable and copper wire  is as follows. 

Transmission Media (Guided): Magnetic Media:

The purpose of physical media is to transport a raw bit stream from one machine to another.
These media are roughly grouped into guided media, such as copper wire and fiber optics, and unguided media, such as radio and lasers through the air. Each one has its own characteristic in terms of bandwidth, delay, cost, and ease of installation and maintenance.

The OSI Reference Model : Network Architecture

This model is developed by the International Standards Organization (ISO) as the first step toward international standardization of the protocols used in the various layers. The model is called the ISO-OSI (Open System Interconnection) Reference Model because it deals with connecting open systems- that is, systems that are open for communication with other systems.

Comparision of OSI and TCP/IP

We have already seen that the OSI reference model and the TCP/IP reference model The OSI and TCP/IP reference models have much in similar such as,
Both are based on the concept of a stack of independent protocol.
The structure or the functionality of the layers is roughly similar.
Despite these fundamental similarities, the two models also have many differences these are as follows.

The TCP/IP Reference Model

History: The ARPANET was a research network sponsored by the DoD (U. S. Department of defense). It connected hundreds of universities and government installations using leased telephone lines.
When satellite and radio networks were added, the existing protocols had trouble interworking with them, so new reference architecture was needed.

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