1. Quiz # 1
Chapters 1,2,3, & 4

2. Analog and Digital Information
Information can be represented in one of two ways: analog or digital
Analog data
A continuous representation, analogous to the actual information it represents
Digital data
A discrete representation, breaking the information up into separate elements

3. Digitization Initially transforming data for computer use
Assigning people social security numbers
The creation of telephone numbers
Encoding information became the way to transform the real world into a context that the computer could understand

4. Information Metamorphosis
Fitting the real world into the computer
Computer’s world
Electronic
Fast
Binary
Real World
Multiple forms of data / information
Imprecise / vague
Non uniform speeds

5. Information Metamorphosis
Real World Data Forms
Numeric Data
Character Data
Graphical / Visual Data
Audio Data
Instructional Data
Methodology needed to transform real world data into computer world (binary)

6. Binary Number System Binary for numeric data Binary digit = Bit
8 Bits = Byte
Smallest addressable unit within the computer
4 Bytes = Word
Basic unit for arithmetic
Contains 32 bits
Converting from binary

7. Numeric Data Converting to binary Repeated division by 2
Remainders are the important part
Read from bottom up as if left to right

8. Character Data Binary for Character Data
8 bit combinations assigned to a symbol
Name for mapping process is ASCII table

9. Graphical Data
Binary for Graphical Data

10. Graphical Data
Binary for Graphical Data

11. Graphical Data Binary for Graphical Data
Each black pixel is represented as a “1”
Each white pixel is represented as a “0”
Pixels are grouped in units of 8 so they can be stored in 1 byte

12. Graphical Data A 1” picture scanned at 150 DPI (dots per inch)
Total size = 150 X 150  22,500 dots
Memory required = 22,500 / 8  2,813 bytes
Color requires more bits to represent each dot
Using 8 bits for each dot allows for 256 different colors
The 1” picture now requires 22,500 bytes

13. Graphical Data Printers are rated in DPI for print quality
Scanners are rated in DPI for image resolution
Monitors / displays have display settings for display resolution
800 X 600
1024 X 768
1280 X 1024
1400 X 1050

14. Audio Data Binary for audio data Sound as a waveform
Y-axis represents voltage
X-axis represents time
Suppose the wave form shown represents 1 second of sound

15. Audio Data
Divide Sample into segments

16. Audio Data
Divide Sample into more segments

17. Audio Data
Divide Sample into even more segments

18. Audio Data The more segments the better the re-created wave form
The given sample was divided into 34 segments (approx)
An Audio CD utilizes 44,000 samples per second of sound

19. Instructional Data Binary for Instructional Data
Instructional Data has not only content but sequence
Driving directions to NJ Aquarium
Designated number of steps
Sequence of steps is critical to success
Rearranging sequence will not get you to the NJ Acquarium
Recipe / Directions / Program

20. The Unicode Character Set
Extended ASCII is not enough for international use
One Unicode mapping uses 16 bits per character
How many characters can this mapping represent?
Unicode is a superset of ASCII
The first 256 characters correspond exactly to the extended ASCII character set

21. Keyword Encoding
Replace frequently used words with a single character

22. Run-Length Encoding
A single character may be repeated over and over again in a long sequence
Replace a repeated sequence with
a flag character
repeated character
number of repetitions
*n8
* is the flag character
n is the repeated character
8 is the number of times n is repeated

23. Huffman Encoding
In Huffman encoding no character's bit string is the prefix of any other character's bit string
To decode
look for match left to right, bit by bit
record letter when a match is found
begin where you left off,going left to right

24. Digitized Images and Graphics
Digitizing a picture
Representing it as a collection of individual dots called pixels
Resolution
The number of pixels used to represent a picture
Raster Graphics
Storage of data on a pixel-by-pixel basis
Bitmap (BMP), GIF, JPEG, and PNG are raster-grahics formats

25. Digitized Images and Graphics
Bitmap format
Contains the pixel color values of the image from left to right and from top to bottom
GIF format (indexed color)
Each image is made up of only 256 colors
JPEG format
Averages color hues over short distances
PNG format
Like GIF but achieves greater compression with wider range of color depths
Which is better for line drawings? Pictures?

26. Vector Graphics Vector graphics
A format that describes an image in terms of lines and geometric shapes
A vector graphic is a series of commands that describe a line’s direction, thickness, and color
The file sizes tend to be smaller because not every pixel is described

27. Vector Graphics The good side and the bad side…
Vector graphics can be resized mathematically and changes can be calculated dynamically as needed
Vector graphics are not good for representing real-world images

28. Computers and Electricity
Gate
A device that performs a basic operation on
electrical signals
Circuits
Gates combined to perform more
complicated tasks

29. Computers and Electricity
How do we describe the behavior of gates and circuits?
Boolean expressions
Uses Boolean algebra, a mathematical notation for expressing two-valued logic
Logic diagrams
A graphical representation of a circuit; each gate has its
own symbol
Truth tables
A table showing all possible input value and the associated
output values

30. NOT Gate
A NOT gate accepts one input signal (0 or 1) and returns the opposite signal as output
Figure 4.1 Various representations of a NOT gate

31. AND Gate An AND gate accepts two input signals
If both are 1, the output is 1; otherwise,
the output is 0
Figure 4.2 Various representations of an AND gate

32. OR Gate An OR gate accepts two input signals
If both are 0, the output is 0; otherwise,
the output is 1
Figure 4.3 Various representations of a OR gate

33. XOR Gate An XOR gate accepts two input signals
If both are the same, the output is 0; otherwise,
the output is 1
Figure 4.4 Various representations of an XOR gate

34. NAND Gate The NAND gate accepts two input signals
If both are 1, the output is 0; otherwise,
the output is 1
Figure 4.5 Various representations of a NAND gate

35. NOR Gate The NOR gate accepts two input signals
If both are 0, the output is 1; otherwise,
the output is 0
Figure 4.6 Various representations of a NOR gate

36. Combinational Circuits
Gates are combined into circuits by using the output of one gate as the input for another

37. Combinational Circuits
Three inputs require eight rows to describe all possible input combinations
This same circuit using a Boolean expression is (AB + AC)

38. Combinational Circuits
Consider the following Boolean expression A(B + C)
Does this truth table look familiar?
Compare it with previous table

39. Combinational Circuits
Circuit equivalence
Two circuits that produce the same output for identical input
Boolean algebra allows us to apply provable mathematical principles to help design circuits
A(B + C) = AB + BC (distributive law) so circuits must be equivalent

40. Adders
The result of adding two binary digits could produce a carry value
Recall that = 10 in base two
Half adder
A circuit that computes the sum of two bits and produces the correct carry bit
Truth table

41. Adders sum = A  B carry = AB
Circuit diagram representing a half adder
Boolean expressions
sum = A  B
carry = AB

42. Adders Full adder A circuit that takes the carry-in value into account
Figure A full adder

43. Circuits as Memory
The design of this circuit guarantees that the two outputs X and Y are always complements of each other
The value of X at any point in time is considered to be the current state of the circuit
Therefore, if X is 1, the circuit is storing a 1; if X is 0, the circuit is storing a 0
Figure An S-R latch

44. Ethical Issues Email Privacy Explain why privacy is an illusion.
Who can read your ?
Do you send personal from work?
Does everyone in your family use ?