representing nonnumeric data everything is really a number
TRANSCRIPT
Representing Nonnumeric Data
Everything is really a number
Its all 1’s and 0’s
• How do we represent other things? • Words/Pictures/Sound?• The trick is to come up with an encoding
scheme…
Text
• To store English we need– Letters (upper case & lower)– Punctuation– Special marks (space, newline, etc…)
• Assigned each a number between 0 and 127– A is 65, B is 66…– a is 97, b is 98…
• ASCII encoding : most popular such scheme
ASCII tableDEC OCT HEX BIN Symbol
47 057 2F 00101111 /
48 060 30 00110000 0
49 061 31 00110001 1
50 062 32 00110010 2
51 063 33 00110011 3
52 064 34 00110100 4
53 065 35 00110101 5
54 066 36 00110110 6
55 067 37 00110111 7
56 070 38 00111000 8
57 071 39 00111001 9
58 072 3A 00111010 :
59 073 3B 00111011 ;
60 074 3C 00111100 <
61 075 3D 00111101 =
62 076 3E 00111110 >
63 077 3F 00111111 ?
64 100 40 01000000 @
65 101 41 01000001 A
66 102 42 01000010 B
67 103 43 01000011 C
68 104 44 01000100 D
69 105 45 01000101 E
70 106 46 01000110 F
71 107 47 01000111 G
72 110 48 01001000 H
73 111 49 01001001 I
• Partial table • Full Table:
http://www.ascii-code.com/
• A = 65 = 01000001
• My name:A n d r e w
01000001 01101110 01100100 01110010 01100101 01110111
Text
• Why 0-127?– Well it seemed like enough– 127 is 2^7 – the biggest number you can write with 7
binary digits.
• Need more characters?– Extended ASCII – 8 bits (1 byte) – 256 characters – Unicode – universal scheme – up to 4 bytes per character
http://unicode-table.com/en/#devanagari
Basic Types of Graphics
• Two basic types of 2D graphicBitmap Vector
Bitmaps
• Image divided into pixels– Each pixel either on (1) or off (0)
Adding gray
• 2 digits for each square give 4 “colors” (00, 01, 10, 11)
Adding gray
• 2 digits for each square give 4 “colors” (00, 01, 10, 11)
Image Size
Image is 2000 pixels wide & 1000 pixels tall.
2000 x 1000 = 2,000,000 pixels
Bits per Pixel 24 8 8 1
Number Colors 16,777,216 256 (color) 256 (grays) 2
Image Size 48,000,000 bitsor ~5.7 MBytes
16,000,000 bitsor ~1.9 MBytes
16,000,000 bitsor ~1.9 MBytes
2,000,000 bitsor ~244 KBytes
Vector Art
• Vector images are mathematically based– Everything described as lines and curves– Shapes are filled with solid color, gradients or patterns
Computer Sounds
• Two approaches to representing sound as numbers:– MIDI sequences– Samples
MIDI
• Musical Instrument Digital Interface– Sheet music for your computer. – Does not store actual sounds – just instructions for
generating the sounds.• Very compact• Been around since the 60’s
Samples
• Sounds are just pressure waves:
Samples
• Simulate a wave with lots of data points– Intensities at points in time– Computer reconstructs wave from points