1. Copyright © 2015 Pearson Education, Inc. Chapter 1: Data Storage

2. Copyright © 2015 Pearson Education, Inc. 1.1 Bits and Their Storage 1.2 Main Memory 1.3 Mass Storage 1.4 Representing Information as Bit Patterns 1.5 The Binary System Chapter 1: Data Storage 1-2

3. Copyright © 2015 Pearson Education, Inc. 1.6 Storing Integers 1.7 Storing Fractions 1.8 Data and Programming 1.9 Data Compression 1.10 Communications Errors Chapter 1: Data Storage (continued) 1-3

4. Copyright © 2015 Pearson Education, Inc. Ask TA Mine: Monday 11-2 in room 135 or 129 maybe, not sure. (ask Rasha, the admin) Syllabus Office Hours 1-4

5. Copyright © 2015 Pearson Education, Inc. 0-5

6. Copyright © 2015 Pearson Education, Inc. 0-6

7. Copyright © 2015 Pearson Education, Inc. 0-7

8. Copyright © 2015 Pearson Education, Inc. Bit: Binary Digit (0 or 1) Bit Patterns are used to represent information –Numbers –Text characters –Images –Sound –And others Bits and Bit Patterns 1-8

9. Copyright © 2015 Pearson Education, Inc. Boolean Operation: An operation that manipulates one or more true/false values Specific operations –AND –OR –XOR (exclusive or) –NOT Boolean Operations 1-9

10. Copyright © 2015 Pearson Education, Inc. Figure 1.1 The possible input and output values of Boolean operations AND, OR, and XOR (exclusive or) 1-10 The NOT operation NOT 1 NOT 0 0 1

11. Copyright © 2015 Pearson Education, Inc. Figure 1.1 The possible input and output values of Boolean operations AND, OR, and XOR (exclusive or) 1-11 AND OR XOR 1 1 ▬► 1 1 0 ▬► 1 0 1 ▬► 1 1 0 ▬► 1 0 1 ▬► 1

12. Copyright © 2015 Pearson Education, Inc. Gate: A device that computes a Boolean operation –Often implemented as (small) electronic circuits –Provide the building blocks from which computers are constructed –VLSI (Very Large Scale Integration) Gates 1-12

13. Copyright © 2015 Pearson Education, Inc. Figure 1.2 A pictorial representation of AND, OR, XOR, and NOT gates as well as their input and output values 1-13

14. Copyright © 2015 Pearson Education, Inc. Flip-flop: A circuit built from gates that can store one bit. –One input line is used to set its stored value to 1 –One input line is used to set its stored value to 0 –While both input lines are 0, the most recently stored value is preserved Flip-flops 1-14

15. Copyright © 2015 Pearson Education, Inc. Figure 1.3 A simple flip-flop circuit 1-15

16. Copyright © 2015 Pearson Education, Inc. Figure 1.4 Setting the output of a flip-flop to 1 1-16

17. Copyright © 2015 Pearson Education, Inc. Figure 1.4 Setting the output of a flip-flop to 1 (continued) 1-17

18. Copyright © 2015 Pearson Education, Inc. Figure 1.4 Setting the output of a flip-flop to 1 (continued) 1-18

19. Copyright © 2015 Pearson Education, Inc. Figure 1.5 Another way of constructing a flip-flop 1-19

20. Copyright © 2015 Pearson Education, Inc. Hexadecimal notation: A shorthand notation for long bit patterns –Divides a pattern into groups of four bits each –Represents each group by a single symbol Example: 10100011 becomes A3 Hexadecimal Notation 1-20

21. Copyright © 2015 Pearson Education, Inc. Figure 1.6 The hexadecimal coding system 1-21

22. Copyright © 2015 Pearson Education, Inc. Cell: A unit of main memory (typically 8 bits which is one byte) –Most significant bit: the bit at the left (high- order) end of the conceptual row of bits in a memory cell –Least significant bit: the bit at the right (low- order) end of the conceptual row of bits in a memory cell 1.2 Main Memory Cells 1-22

23. Copyright © 2015 Pearson Education, Inc. Figure 1.7 The organization of a byte-size memory cell 1-23

24. Copyright © 2015 Pearson Education, Inc. Address: A “name” that uniquely identifies one cell in the computer’s main memory –The names are actually numbers. –These numbers are assigned consecutively starting at zero. –Numbering the cells in this manner associates an order with the memory cells. Main Memory Addresses 1-24

25. Copyright © 2015 Pearson Education, Inc. Figure 1.8 Memory cells arranged by address 1-25

26. Copyright © 2015 Pearson Education, Inc. Random Access Memory (RAM): Memory in which individual cells can be easily accessed in any order Dynamic Memory (DRAM): RAM composed of volatile memory Memory Terminology 1-26 http://computer.howstuffworks.com/ram1.htm

27. Copyright © 2015 Pearson Education, Inc. Kilobyte: 2 10 bytes = 1024 bytes –Example: 3 KB = 3 times1024 bytes Megabyte: 2 20 bytes = 1,048,576 bytes –Example: 3 MB = 3 times 1,048,576 bytes Gigabyte: 2 30 bytes = 1,073,741,824 bytes –Example: 3 GB = 3 times 1,073,741,824 bytes Measuring Memory Capacity 1-27

28. Copyright © 2015 Pearson Education, Inc. Measuring Memory Capacity 1-28 A petabyte is (1,000,000,000,000,000) bytes A terabyte is a trillion bytes (1,000,000,000,000) A exabyte is (1,000,000,000,000,000,000) bytes A zettabyte is (1,000,000,000,000,000,000,000) bytes

29. Copyright © 2015 Pearson Education, Inc. Are devices for storing data permanently. Advantages over main memory –Less volatility –Larger storage capacities –Low cost –In many cases can be removed 1.3 Mass Storage 1-29

30. Copyright © 2015 Pearson Education, Inc. Magnetic Devices –Magnetic disks –Magnetic tape Optical Devices –CDs –DVDs –Blu Ray Solid State Devices –Flash drives –Solid-state disks (SDD) 1.3 Mass Storage 1-30

31. Copyright © 2015 Pearson Education, Inc. Figure 1.9 A magnetic disk storage system 1-31

32. Copyright © 2015 Pearson Education, Inc. 32 Magnetic Disks Bits of data (0’s and 1’s) are stored on circular magnetic platters called disks. A disk rotates rapidly (& never stops). A disk head reads and writes bits of data as they pass under the head. Often, several platters are organized into a disk pack (or disk drive).

33. Copyright © 2015 Pearson Education, Inc. 33 A Disk Drive Disk drive with 4 platters and 8 surfaces and 8 RW heads surfaces Spindle Boom Read/Write heads

34. Copyright © 2015 Pearson Education, Inc. 34 Looking at a surface Surface of disk showing tracks and sectors sector tracks

35. Copyright © 2015 Pearson Education, Inc. 35 Organization of Disks Disk contains concentric tracks. Tracks are divided into sectors A sector is the smallest addressable unit in a disk.

36. Copyright © 2015 Pearson Education, Inc. 36 Disk Controller Disk controllers: typically embedded in the disk drive, which acts as an interface between the CPU and the disk hardware. The controller has an internal cache (typically a number of MBs) that it uses to buffer data for read/write requests.

37. Copyright © 2015 Pearson Education, Inc. Structure of Hard Disk

38. Copyright © 2015 Pearson Education, Inc. Figure 1.10 CD storage 1-38 http://www.explainthatstuff.com/how-cd- writers-work.html

39. Copyright © 2015 Pearson Education, Inc. 39 Physical Organization of CD-ROM Compact Disk – read only memory (write once) Data is encoded and read optically with a laser Can store around 600MB data Digital data is represented as a series of Pits and Lands: 1.Pit = a little depression, forming a lower level in the track 2. Land = the flat part between pits, or the upper levels in the track

40. Copyright © 2015 Pearson Education, Inc. 40 Organization of data Reading a CD is done by shining a laser at the disc and detecting changing reflections patterns. –1 = change in height (land to pit or pit to land) –0 = a “fixed” amount of time between 1’s LANDPITLANDPITLAND...------+ +-------------+ +---... |_____| |_______|..0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 1 0 0.. Note : we cannot have two 1’s in a row! => uses Eight to Fourteen Modulation (EFM) encoding table.

41. Copyright © 2015 Pearson Education, Inc. 41 Properties Note that: Since 0's are represented by the length of time between transitions, we must travel at constant linear velocity (CLV)on the tracks. Sectors are organized along a spiral Sectors have same linear length Advantage: takes advantage of all storage space available. Disadvantage: has to change rotational speed when seeking (slower towards the outside)

42. Copyright © 2015 Pearson Education, Inc.

43. Flash Memory – circuits that traps electrons in tiny silicon dioxide chambers Repeated erasing slowly damages the media Mass storage of choice for: –Digital cameras SD Cards provide GBs of storage Flash Drives 1-43 –Smartphones

44. Copyright © 2015 Pearson Education, Inc. Each character (letter, punctuation, etc.) is assigned a unique bit pattern. –ASCII: Uses patterns of 7-bits to represent most symbols used in written English text –ISO developed a number of 8 bit extensions to ASCII, each designed to accommodate a major language group –Unicode: Uses patterns up to 21-bits to represent the symbols used in languages world wide, 16-bits for world’s commonly used languages 1.4 Representing Text 1-44

45. Copyright © 2015 Pearson Education, Inc. Figure 1.11 The message “Hello.” in ASCII or UTF-8 encoding 1-45

46. Copyright © 2015 Pearson Education, Inc. Binary notation: Uses bits to represent a number in base two Limitations of computer representations of numeric values –Overflow: occurs when a value is too big to be represented –Truncation: occurs when a value cannot be represented accurately Representing Numeric Values 1-46

47. Copyright © 2015 Pearson Education, Inc. Bit map techniques –Pixel: short for “picture element” –RGB –Luminance and chrominance Vector techniques –Scalable –TrueType and PostScript https://www.youtube.com/watch?v=fy9Pby0Gzsc Representing Images 1-47

48. Copyright © 2015 Pearson Education, Inc. Sampling techniques –Used for high quality recordings –Records actual audio MIDI –Used in music synthesizers –Records “musical score” Representing Sound 1-48

49. Copyright © 2015 Pearson Education, Inc. Figure 1.12 The sound wave represented by the sequence 0, 1.5, 2.0, 1.5, 2.0, 3.0, 4.0, 3.0, 0 1-49

50. Copyright © 2015 Pearson Education, Inc. The traditional decimal system is based on powers of ten. The Binary system is based on powers of two. 1.5 The Binary System 1-50

51. Copyright © 2015 Pearson Education, Inc. Figure 1.13 The base ten and binary systems 1-51

52. Copyright © 2015 Pearson Education, Inc. 0-52

53. Copyright © 2015 Pearson Education, Inc. 0-53

54. Copyright © 2015 Pearson Education, Inc. Figure 1.14 Decoding the binary representation 100101 1-54

55. Copyright © 2015 Pearson Education, Inc. Figure 1.15 An algorithm for finding the binary representation of a positive integer 1-55

56. Copyright © 2015 Pearson Education, Inc. Figure 1.16 Applying the algorithm in Figure 1.15 to obtain the binary representation of thirteen 1-56

57. Copyright © 2015 Pearson Education, Inc. Figure 1.17 The binary addition facts 1-57

58. Copyright © 2015 Pearson Education, Inc. Figure 1.18 Decoding the binary representation 101.101 1-58

59. Copyright © 2015 Pearson Education, Inc. Two’s complement notation: The most popular means of representing integer values Excess notation: Another means of representing integer values Both can suffer from overflow errors 1.6 Storing Integers 1-59

60. Copyright © 2015 Pearson Education, Inc. Figure 1.19 Two’s complement notation systems 1-60

61. Copyright © 2015 Pearson Education, Inc. Figure 1.20 Coding the value -6 in two’s complement notation using four bits 1-61

62. Copyright © 2015 Pearson Education, Inc. Figure 1.21 Addition problems converted to two’s complement notation 1-62

63. Copyright © 2015 Pearson Education, Inc. Figure 1.22 An excess eight conversion table 1-63

64. Copyright © 2015 Pearson Education, Inc. 0-64

65. Copyright © 2015 Pearson Education, Inc. Figure 1.23 An excess notation system using bit patterns of length three 1-65

66. Copyright © 2015 Pearson Education, Inc. Floating-point Notation: Consists of a sign bit, a mantissa field, and an exponent field. Related topics include –Normalized form –Truncation errors 1.7 Storing Fractions 1-66

67. Copyright © 2015 Pearson Education, Inc. Figure 1.24 Floating-point notation components 1-67

68. Copyright © 2015 Pearson Education, Inc. Figure 1.25 Encoding the value 2 5 ⁄ 8 1-68

69. Copyright © 2015 Pearson Education, Inc. A programming language is a computer system created to allow humans to precisely express algorithms using a higher level of abstraction. 1.8 Data and Programming 1-69

70. Copyright © 2015 Pearson Education, Inc. Python: a popular programming language for applications, scientific computation, and as an introductory language for students Freely available from www.python.org Python is an interpreted language –Typing: print('Hello, World!') –Results in: Hello, World! Getting Started with Python 1-70

71. Copyright © 2015 Pearson Education, Inc. Variables: name values for later use Analogous to mathematic variables in algebra s = 'Hello, World!' print(s) my_integer = 5 my_floating_point = 26.2 my_Boolean = True my_string = 'characters' my_integer = 0xFF Variables 1-71

72. Copyright © 2015 Pearson Education, Inc. print(3 + 4) # Prints 7 print(5 – 6) # Prints -1 print(7 * 8) # Prints 56 print(45 / 4) # Prints 11.25 print(2 ** 10) # Prints 1024 s = 'hello' + 'world' s = s * 4 print(s) Operators and Expressions 1-72

73. Copyright © 2015 Pearson Education, Inc. # A converter for currency exchange. USD_to_GBP = 0.66 # Today's exchange rate GBP_sign = '\u00A3' # Unicode value for £ dollars = 1000 # Number dollars to convert # Conversion calculations pounds = dollars * USD_to_GBP # Printing the results print('Today, $' + str(dollars)) print('converts to ' + GBP_sign + str(pounds)) Currency Conversion 1-73

74. Copyright © 2015 Pearson Education, Inc. Syntax errors print(5 +) SyntaxError: invalid syntax pront(5) NameError: name 'pront' is not defined Semantic errors –Incorrect expressions like total_pay = 40 + extra_hours * pay_rate Runtime errors –Unintentional divide by zero Debugging 1-74

75. Copyright © 2015 Pearson Education, Inc. Lossy versus lossless Run-length encoding Frequency-dependent encoding (Variable length encoding) (Huffman codes) Relative encoding Dictionary encoding (Includes adaptive dictionary encoding such as LZW encoding.) 1.9 Data Compression 1-75

76. Copyright © 2015 Pearson Education, Inc. 4, 11 4, 9, 2, 1 4, 11 4, 9 5, 7 0, 17 1, 15 Run Length Encoding Example 0-76

77. Copyright © 2015 Pearson Education, Inc. 0-77 Run Length Encoding Example

78. Copyright © 2015 Pearson Education, Inc. Huffman Codes –Letters with high frequency are encoded using shorter symbols. –Letters with low frequency are encoded using longer symbols. –Huffman code (for a set of seven letters): four bits per letter (minimum 3 bits). –The string “abefd” is encoded as “1010000100100000”. –Huffman codes are used in some UNIX systems for data compression.

79. Copyright © 2015 Pearson Education, Inc. LZW Example 0-79 xxy yyx xxy xxy yyx 1123221343435

80. Copyright © 2015 Pearson Education, Inc. GIF: Good for cartoons JPEG: Good for photographs TIFF: Good for image archiving Compressing Images 1-80

81. Copyright © 2015 Pearson Education, Inc. MPEG –High definition television broadcast –Video conferencing MP3 –Temporal masking –Frequency masking Compressing Audio and Video 1-81

82. Copyright © 2015 Pearson Education, Inc. EndofChapter