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

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

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 = = = = =

Convert the following numbers: to decimal number to binary number (using 8 bits)

Numbers are stored in memory. Main memory is divided into many memory locations (or cells) Each memory cell has a numeric address, which uniquely identifies it

Storing Information Large values are stored in consecutive memory locations Each 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, 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 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

Make a truth table for voting. People can vote if they are a citizen, are 18 and are registered.

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.

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.)