How many computers do you have?

All digital electronics use computers.

Computer CD & DVD players IPod Cell phone HDTV Digital cameras

What industry is the biggest user of computers?

Car may have over 50 computers

What are the main parts of a computer?

Computers hold a collection of numbers.

Computers store and manipulate numbers.

What do we mean by digital?

What are examples of analog processes or systems?

Sound, water flow, electric power, role a tire. What are examples of digital processes or systems?

Walk, light switch (except dimmer), pregnant.

Why do computers use binary numbers?

Binary numbers are easy to represent electrically.

on / off like a light switch

Binary numbers are accurate. Binary numbers can be

transmitted accurately. Binary numbers are easily

manipulated. math & logic

3V?

1V, 1V

21 20

How does a computer handle information?

Look at word processing as an example. As you type a word, every character is stored as a

number, including spaces, digits, and punctuation.

Upper and lower case letters are separate characters.

H i , H e a t h e r .

72 105 44 32 72 101 97 116 104 101 114 46

ASCII code

How are numbers stored?

Computers use binary numbers. Binary numbers use bits, each representing a power of 2.

How high can you count on one hand?

To five using decimal system.

You can count to 31 with binary system.

0

123

4

20 = 1

21 = 222 = 423 = 8

24 = 16

1+2+4+8

+16 31

Convert the following numbers:

10101101 to decimal number.173

93 to binary number (using 8 bits).01011101

Numbers are stored in memory.

Main memory is divided into many memory locations (or cells)

927892799280928192829283928492859286

Each memory cell has a numeric address, which uniquely identifies it

Storing Information

927892799280928192829283928492859286

Large values arestored in consecutivememory locations

1001101010011010Each memory cell stores a set number of bits (usually 8, 16 or 32 bits)

Music is also converted to numbers.

CD music may be encoded as 44.1 kHz, 705.6 kbps.

The music is 'sliced' 44,100 times a second.

The rate determines how many bits can be filled per second.

16 bits means the height range is 65,536 different values for each sample.

The finer the grid, the better the digital representation.

To recreate an analog signal, need good digitization.

Data compression, like MP3, reduces the bit rate.

Almost any operation can be broken down into a series of yes/no decisions.

Digital electronics make logic decisions.

A fire alarm sounds if it senses heat or smoke. You can go to the movie if you have $10 and if you

can find a ride to the theater. People can vote if they are a citizen, are 18 and are

registered.

How does a computer handle this?

A fire alarm sounds if it senses heat or smoke. Two conditions - heat OR smoke. One action - sound the alarm

heat smoke alarmno no noyes no yesno yes yesyes yes yes

heat smoke alarm0 0 01 0 10 1 11 1 1

yes = 1

no = 0

Truth table for going to a movie.

You can go to the movie if you have $10 and you have a ride.

Two conditions - $10 AND ride. One action – see movie

Have $10 Have ride Go movieno no noyes no nono yes noyes yes yes

Hav $10 Have ride Go movie0 0 01 0 00 1 01 1 1

Make a truth table for voting.

People can vote if they are a citizen, are 18 and are registered.

Citizen18 years old

Registered to vote Vote

0 0 0 00 0 1 00 1 0 00 1 1 01 0 0 01 0 1 01 1 0 01 1 1 1

Make a truth table for going to a movie.

You can go to the PG movie if you have $10 and if you are over 18 or accompanied by a parent.

You have $10

You are over 18

Have Parent

Go to movie

0 0 0 00 0 1 00 1 0 00 1 1 01 0 0 01 0 1 11 1 0 11 1 1 1

You are over 18

Have parent OR

0 0 00 1 11 0 11 1 1

Toxic Waste Incinerator

The intense heat of the fire is neutralizes the toxicity of the waste introduced into the incinerator.

Suppose we were given the task of designing a flame detection circuit for a toxic waste incinerator.

So long as a flame is maintained in the incinerator, it is safe to inject waste into it to be neutralized.

Write truth table for safe operation.

Failure of a single sensor does not lead to an emission of toxins out the exhaust.

Action = open valve Condition = 3 sensors on

Write truth table for safe but economical operation.

Want at least two sensors showing flame to open waste valve. Action = open valve Condition = 2 sensors on

But need to add a check for bad sensors.

Do all sensors agree? Add a second output

to show sensor agreement.

Homework - Write Truth Tables for toy car.

You will design a simple digital circuit to make a toy car follow a flashlight. The car has three light sensors looking right, center, and left. The car has two motors to drive the right and left wheels.

Make a truth table with three inputs and two outputs, as shown below. (Please use these columns to simplify troubleshooting.)

R Sensor L Sensor C Sensor L Wheel R Wheel