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IT 101

Spring, 2005Department of Electrical and Computer

Engineering

Lecture Notes - 1

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Course Objectives

To provide students with an understanding of the evolution of information technology and its role in modern society.

To introduce fundamental concepts and components of information technology, such as computer architectures, networking, and telecommunications.

To provide exposure to the quantitative aspects of information technology and teach students to perform some of IT’s basic computational tasks.

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Introductions

Instructor: Laura DeNardis Contact Information: ldenardi@gmu.edu Office Hours: By Appointment in Science and Tech.

II, Room 235 Teaching Assistant: Ramya Sree Kanakamedala. Student Questionnaire

Name and class year Major; full or part time status; employment Math background Reason for taking IT 101 IT topics that interest you

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Administrative Matters

Required Text: “Information Technology: Inside and Outside” by David Cyganski and John A. Orr with Richard F. Vaz, Prentice Hall, 2001.

Optional Text: “The Digital Information Age” by Roman Kuc, PWS, 1999.

Required Equipment: A calculator (e.g. Casio, TI) and a computer with web access.

Course Web Site: Selected lectures, homework, schedule, and announcements will be posted on the IT 101 Section 2 web site. http://ece.gmu.edu/ececourses/it101/prah.html.

Class Environment: Turn off cell phones and personal communication devices.

Attendance: Class begins promptly at 7:20 p.m. Please arrive on time and attend all lectures for maximum learning. (Some exam questions will draw exclusively from class lectures.)

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Grading Policy

Averages will be calculated as follows: Exam 1: 25% (February 23) Exam 2: 25% (April 6) Homework: 15% Comprehensive Final Exam: 35%

(May 11)

No exam rescheduling will be possible because of class size.

All exams will be closed book, closed notes.

If the University is officially closed for snow or emergency on an exam date, the exam will be held the following class period.

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Honor Code

THE GEORGE MASON UNIVERSITY HONOR CODE WILL BE STRONGLY ENFORCED WITHOUT EXCEPTION.

Absolutely no cheating.

All students have the duty as participating members of the GMU community to report Honor Code violations.

Homework and exams must be individual effort.

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Course Outline

Understanding terminology Examples of information systems Significance of digital technology

Module I

INTRODUCTION TO INFORMATION

SYSTEMS Representing numbers, text, images, and video in binary

Converting analog to digital

Module II

BINARY REPRESENTATION AND INFORMATION CODING

Module III

Local area networks

Wide area networks

The Internet Network securityModule IV

COMPUTER NETWORKING

The phone system Wireless

telephony Convergence of

voice and dataModule V

TELECOMMUNICATIONS

History of computing

Computer system components

Computer software

COMPUTER ARCHITECTURE

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The Information Age

Day-to-Day Living – Online shopping, virtual education, telecommuting, online banking and bill payment, online course registration, airline reservations.

Entertainment – Television, movies, radio, CDs, video cameras, computer games, web surfing.

Social Life – Web communities, online dating, instant messaging, email, cell phones, personal communication devices.

Economics – IT use in business and government has engendered significant productivity increases. The IT industry itself (dot-com implosion not withstanding) has become a major economic sector.

Today, information technology touches every aspect of our lives.

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Information Technology:According to WhatIs.com

IT (information technology) is a term that encompasses all forms of technology used to create, store, exchange, and use information in its various forms (business data, voice conversations, still images, motion pictures, multimedia presentations, and other forms, including those not yet conceived). It's a convenient term for including both telephony and computer technology in the same word. It is the technology that is driving what has often been called "the information revolution."

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Information System Example

Breakthrough in the communication of information (sound).

Invented by Thomas Edison. A diaphragm vibrates when it detects sound waves. The diaphragm transfers a vibration to a stylus, which cuts

grooves into a solid material.

Cylinder

Needle

DiaphragmSound Collecting Horn

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Information System Example

The telephone was invented by Alexander Graham Bell in 1876

Transmitter Receiver

Transmission Media

Switching and Signaling System

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Information System Example

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Components of Information Systems

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Components of Information Systems

Input Transducer(s) - Also known as a sensor. Converts a physical signal to an electrical, electromechanical, mechanical, optical, or electromagnetic signal.

Transmitter - A device that sends the transduced signal to a receiver.

Transmission Channel - A physical medium by which a signal is carried.

Receiver - A device that recovers a transmitted signal from the transmission channel.

Output Transducer - A device that converts the received signal back into a useful physical quantity.

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Signals v. Messages v. Information

Signal – A physical representation of a process. Examples include sound waves, light pulse, electronic impulses, etc.

Message – The content of the signal. Examples include binary representation, alphanumeric characters, etc.

Information – Whatever the content of the message conveys to the observer.

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Analog Versus Digital

Exists at SPECIFIC POINTS in space and time

Variables can have ONLY SPECIFIC values

Example: Clock hand that rotates in jumps (ticks)

Exists for ALL values of space and time

Variables can have ALL POSSIBLE values

Example: smoothly rotating hand on a clock

DISCRETE CONTINUOUS

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Analog and Digital Technologies

Digital ThermometerMercury Thermometer

DVDVCR

CDVinyl Record

CalculatorSlide Rule

Digital ClockAnalog Clock

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The Natural World is Analog

This continuous acoustical waveform can be detected by a device and converted into an analogous electrical waveform for transmission over a circuit.

Human speech is an example of analog communication.Speech causes air to vibrate with varying amplitude (volume) and frequency (pitch).

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The Computer World is Digital

Digital computers communicate using 2 discrete values. In other words, they speak in binary (0 and 1).

Of course, 0s and 1s are not literally transmitted In an electrical network, variations in voltage represent one of the

two discrete values. In an optical network, pulses of light provide the discrete values.

Recall that the 0s and 1s are the “message” and the pulses of light or voltage variations are the “signal.”

Two values in different combinations sufficiently encode text, numbers, image, and video!

Note that the telegraph was an early example of communications using discrete, electrical pulse transmission.

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A Problem with Analog

Analog signal

Noise

If an analog signal provides such a close representation of information sources, why do we use digital?

Analog signal on magnetic tape. Random fluctuations in the magnetic tape add noise to the tone. The tone-like noise components cannot be removed and become part of the subsequent versions of the analog signal.

Distorted Signal(EMI - ElectroMagnetic InterferenceRFI - Radio Frequency Interference)

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The Digital Advantage

Restoration of digital signals stored on magnetic tape. Random fluctuations in the magnetic tape add noise to the digital signal. A processor, called a threshold detector, compares the signal to a threshold (dashed line) and decides that the data value is a 1 if the signal lies above the threshold, or a 0, otherwise.

Digital Signal Noise Distorted Signal

ThresholdDetector

Regenerated Digital SignalProcessor

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The Digital Advantage

As shown in the previous slide, digital information is resistant to signal degradation.

Copying analog information magnifies noise and interference. Digital information can be perfectly regenerated.

Analog signals can be scrambled (through frequency mixing) to provide some security.

Digital signals can be manipulated with complex encryption algorithms for much improved security.

Digital information can be easily compressed, providing more efficient transmission.

Digital information systems are cheaper than analog systems.

Management features can be designed into digital signals.

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Digital Computers Speak in Binary Code

To capture information for storage, manipulation, or transmission, we require a process of encoding the information.

One example of a code is the alphabet, which uses: 26 lower case characters 26 upper case characters 10 numbers 32 special characters

Another example of a code is binary, a code with only two distinct symbols in its alphabet.

Digital computers process, store, and communicate information using binary code. In other words, computers speak in binary.

A “bit” is an individual 1 or 0. Bit stands for “binary digit.”

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Why Use a Code with Only Two Values?

A binary system is resistant to errors! The two symbols are highly distinguishable from one another. Consider a compact laser disc for music or computer storage:

A CD is comprised of an enormous number of domains, each of which stores one bit.

Each domain either has a smooth surface that reflects the laser or a “pit” which doesn’t reflect the laser. It’s very clear which of the two values is held by each domain.

If, instead of 2 values, each domain held 3 values (domains of zero, partial, and high reflectivity) a simple fingerprint might create errors.

The 2 clear values make the system simple and reliable. Two values correspond well to the “on” and “off” states of

electronic switches that comprise digital computers.

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How do Digital Systems Produce 0s and 1s?

Physically, a 1 or a 0 can be produced in several ways: The presence of or level of voltage in an electrical network. A pulse of light or varying of light intensity in an optical network. Discrete variations of signal amplitude in a radio network like

satellite or cellular. STORAGE - To store binary data, storage media must represent two

values. Magnetic disk can be magnetized in two directions “up” or “down” Laser disk domains have either a smooth surface or pitted surface.

TRANSMISSION - Two distinct electrical or optical quantities are transmitted such as a pulse of light and absence of light.

PROCESSING - Computer circuits can be broken down into the fundamental building block, the electronic switch (either “on” or “off”).

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Practical Use

Everyday stuff measured in bits: 32-bit sound card 64-bit video accelerator card 128-bit encryption in your browser 650 MB CD

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Representing Information in Bits

BInary digiTal symbols (BITs) form a universal language for any:

Numbers Text Sound Images Video Anything else you can imagine…

How is this possible????

To begin with, how can everyday numbers be represented in binary?

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How Do We Normally Represent Numbers?

We normally don’t use Binary Digits (Bits) (in which a single placeholder can hold only 0 or 1) in everyday life.

We use Decimal Digits - a single placeholder can hold one of ten numerical values between 0 and 9.

Digits are combined together into larger numbers. For example: 8,234 is made up of 4 digits. The 4 holds the

“1s place,” the 3 holds the “10s place,” the 2 holds the “100s place” and the 8 holds the “1000s place.”

Before we discuss binary code, let’s think about the number system we use every day.

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The Decimal System

Decimal digits are combined to create larger numbers4,567 => (4 x 103) + (5 x 102) + (6 x 101) + (7 x 100)

10 raised to the power of … 100 =1 101 =10 102 =10x10=100 103 =10x10x10=1,000 104 =10x10x10x10=10,000 and so on

Also called Base-10 system There are other ways of representing numbers other

than using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.

We have ten fingers and use ten

digits! Coincidence?

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Comparing the Decimal Number System to the Binary Number System

While people routinely use decimal digits, computers use binary digits.

The decimal system uses ten numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) to represent all values. The binary system uses two numbers (0 and 1) to represent all values.

In other words, computers use the “base-2” system rather than the “base-10” system.

Counting in binary is simple (different, but simple) because you use powers of two instead of ten. Example follows.

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Binary versus Decimal Numbers

2s p

lace

1s p

lace

4s p

lace

8s p

lace

1 0 1 0 11 0 1 0 1

16s

plac

e

10s

plac

e1s

pla

ce

100s

pla

ce

1,00

0s p

lace

9 5, 1 0 79 5, 1 0 7

10,0

00s

plac

e

9 x 10,000 = 90,000+ 5 x 1,000 = 5,000

+ 1 x 100 = 100+ 0 x 10 = 0

+ 7 x 1 = 7_______________

= 95,107 (10)

1 x 16 = 16+ 0 x 8 = 0+ 1 x 4 = 4+ 0 x 2 = 0+ 1 x 1 = 1

_______________= 21 (10)

Decimal NumberDecimal Number Binary NumberBinary Number

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Determining the Value of a Binary Number

The same as calculating the value of a decimal system number except use powers of two instead of powers of ten.

• The binary number 1101 can be converted to decimal as follows: (1x23) + (1x22) + (0x21) + (1x20) = 8 + 4 + 0 + 1 = 13

1 1 0 1

8 4 2 1

8 4 0 1 = 13

multiply

add

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For understanding binary, it’s helpful to have a good command of powers of 2

20 = 1

21 = 2

22 = 2x2 = 4

23 = 2x2x2 = 8

24 = 2x2x2x2 = 16

25 = 2x2x2x2x2 = 32

26 = 2x2x2x2x2x2 = 64

27 = 2x2x2x2x2x2x2 = 128

28 = 2x2x2x2x2x2x2x2 = 256

29 = 2x2x2x2x2x2x2x2x2 = 512

210 = 2x2x2x2x2x2x2x2x2x2 = 1024

and so on...

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Another Example: Converting Binary to Decimal

A computer generates the following sequence of bits: 110101(2)

How do we convert 110101(2) into decimal?

(1x25) + (1x24) + (0x23) + (1x22) + (0x21) + (1x20) = 32 + 16 + 0 + 4 + 0 + 1 = 53(10)

110101(2) = 53(10)

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In Class Example

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Real World Example: The Internet Address

An Internet address, known as an IP address for “Internet Protocol” is comprised of four binary octets, making it a 32-bit address.

IP addresses, difficult for humans to read in binary format, are often converted to “dotted decimal format.”

To convert the 32-bit binary address to dotted decimal format, divide the address into four 8-bit octets and then convert each octet to a decimal number.

Each octet will have one of 256 values (0 through 255)

Converting a 32-bit Internet address into dotted decimal format

192.48.29.253(IP address in dotted decimal form)

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Real World Example: The Internet Address

Convert the following 32-bit Internet address into dotted decimal format:

01011110000101001100001111011100

1) Divide the IP address into four octets01011110 00010100 11000011 11011100

2) Convert each binary octet into a decimal number01011110 = 64+16+8+4+2 = 9400010100 = 16+4 = 2011000011 = 128+64+2+1 = 19511011100 = 128+64+16+8+4 = 220

3) Write out the decimal values separated by periods94.20.195.220

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Practice Converting an Internet Address

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How Can We Reverse the Process?Converting Decimal to Binary

Sometimes it can be done intuitively. For example:

The decimal number 1 represented in 8-bit binary is: 00000001.

The decimal number 128 represented in 8-bit binary is:

10000000. The decimal number 129 represented in 8-bit binary

is: 10000001.

The decimal number 2 represented in 8-bit binary is: 00000010.

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Conversion from Decimal to Binary

The decimal number 4 represented in 8-bit binary?

The decimal number 6 represented in 8-bit binary?

Think about the following examples:

These examples are intuitively simple, but what are we really doing mathematically?

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Converting a Decimal Number to Binary Convert the Decimal Number 174 to a binary octet

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

Step 1: Compare 174 to 128. 174>128 so place a 1 in the 128s place and subtract 174-128 = 46

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

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Step 2: Compare 46 to 64. 46<64 so place a 0 in the 64s place and continue with 46.

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

11 00

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Reversing the Process: Converting a Decimal Number to Binary

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

Step 3: Compare 46 to 32. 46>32 so place a 1 in the 32s place and subtract 46-32=14

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

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Step 4: Compare 14 to 16. 14<16 so place a 0 in the 16s place and continue with 14.

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

11 00

00 11

00

Step 5: Compare 14 to 8. 14>8 so place a 1 in the 8s place and subtract 14-8=6.

11 00 11

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Reversing the Process: Converting a Decimal Number to Binary

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

00

Step 6: Compare 6 to 4. 6>4 so place a 1 in the 4s place and subtract 6-4=2.

11 00 11 11

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

00

Step 7: Compare 2 to 2. 2=2 so place a 1 in the 2s place and subtract 2-2=0.There is no remainder left to convert, so also place a 0 in the 1s place.

11 00 11 11 11

____ ____ ____ ____ ____ ____ ____ ____

1s place

2s place

4s place

8s place

16s place

32s place

64s place

128s place

0011 00 11 11 11 0011

The decimal number 174 has been converted to the binary number 10101110

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Another Approach: Converting from Decimal to Binary Using BCD

We can also simply represent one number at a time. How can we represent the ten decimal numbers (0-9) in binary code?

NumeralNumeral00112233445566778899

BCD RepresentationBCD Representation00000000000100010010001000110011010001000101010101100110011101111000100010011001

We can represent any integer by a string of binary digits. For example, 749 can be represented in binary as: 011101001001

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In-Class Examples

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Binary Conventions

Most Significant Bit (MSB) and Least Significant Bit (LSB)

Decimal Example: 64 6 is the Most Significant Digit 4 is the Least Significant Digit

Binary: 1000000 1 is the MSB 0 on the right is the LSB

Subscripts: Note that the subscript “2” makes it clear a number is in binary format and the subscript “10” makes it clear a number is in decimal format.

This avoids confusion between a number like 110101 which can either be binary, written as 110101(2) or decimal, written as 110,101(10)

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Something to Remember

“Bits” are often used in terms of a data rate, or speed of information flow:

56 Kilobit per second modem (56 Kbps) A T-1 is 1.544 Megabits per second (1.544 Mbps or 1544 Kbps)

“Bytes” are often used in terms of storage or capacity--computer memories are organized in terms of 8 bits.

256 Megabyte (MB) RAM 40 Gigabyte (GB) hard disk