Data Formats used by Computers ISO – International Standards Organization CSA – Canadian Standards Association ANSI – American National Standards Institute IEEE – Institute for Electrical and Electronics Engineers

1. Data Formats used by Computers
Dr. Kamal Gulati

2. Introduction
• Examples
Real World
Data
Computer
DataInput device
Dear Mom: Keyboard 10110010…
Digital
camera
10110010…

3. Format must be appropriate
• The internal representation must be
appropriate for the type of processing to
take place (e.g., text, images, sound)

4. Rules/Conventions
• Proprietary formats
– Unique to a product or company
– E.g., Microsoft Word, Corel Word Perfect, IBM Lotus
Notes
• Standards
– Evolve two ways:
• Proprietary formats become de facto standards (e.g., Adobe
PostScript, Apple Quick Time)
• Committee is struck to solve a problem (Motion Pictures
Experts Group, MPEG)

5. Standards Organizations
• ISO – International Standards Organization
• CSA – Canadian Standards Association
• ANSI – American National Standards
Institute
• IEEE – Institute for Electrical and
Electronics Engineers
• Etc.

6. Examples of Standards
Type of Data Standards
Alphanumeric ASCII, EBCDIC, Unicode
Image JPEG, GIF, PCX, TIFF
Motion picture MPEG-2, Quick Time
Sound Sound Blaster, WAV, AU
Outline graphics/fonts PostScript, TrueType, PDF

7. Why Standards?
• Standard are “arbitrary”
• They exist because they are
– Convenient
– Efficient
– Flexible
– Appropriate
– Etc.

8. Alphanumeric Data
• Problem: Distinguishing between the number 123
(one hundred and twenty-three) and the characters
“123” (one, two, three)
• Four standards for representing letters (alpha) and
numbers
– BCD – Binary-coded decimal
– ASCII – American standard code for information
interchange
– EBCDIC – Extended binary-coded decimal interchange
code
– Unicode

9. Next 2 slides
Standard Alphanumeric Formats
• BCD
• ASCII
• EBCDIC
• Unicode

10. Binary-Coded Decimal (BCD)
• Four bits per digit Digit Bit pattern
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001
Note: the following
bit patterns are not
used:
1010
1011
1100
1101
1110
1111

11. Example
• 709310 = ? (in BCD)
7 0 9 3
0111 0000 1001 0011

12. Next 22 slides
Standard Alphanumeric Formats
• BCD
• ASCII
• EBCDIC
• Unicode

13. The Problem
• Representing text strings, such as
“Hello, world”, in a computer

14. Codes and Characters
• Each character is coded as a byte
• Most common coding system is ASCII
(Pronounced ass-key)
• ASCII = American National Standard Code
for Information Interchange
• Defined in ANSI document X3.4-1977

15. ASCII Features
• 7-bit code
• 8th bit is unused (or used for a parity bit)
• 27 = 128 codes
• Two general types of codes:
– 95 are “Graphic” codes (displayable on a
console)
– 33 are “Control” codes (control features of the
console or communications channel)

16. ASCII Chart
000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

17. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

18. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL
Most significant bit
Least significant bit

19. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL
e.g., ‘a’ = 1100001

20. 95 Graphic codes
000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

21. 33 Control codes
000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

22. Alphabetic codes
000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

23. Numeric codes
000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

24. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL
Punctuation, etc.

25. “Hello, world” Example
=
=
=
=
=
=
=
=
=
=
=
=
Binary
01001000
01100101
01101100
01101100
01101111
00101100
00100000
01110111
01100111
01110010
01101100
01100100
Hexadecimal
48
65
6C
6C
6F
2C
20
77
67
72
6C
64
Decimal
72
101
108
108
111
44
32
119
103
114
108
100
H
e
l
l
o
,
w
o
r
l
d
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=

26. Common Control Codes
• CR 0D carriage return
• LF 0A line feed
• HT 09 horizontal tab
• DEL 7F delete
• NULL 00 null
Hexadecimal code

27. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

28. Terminology
• Learn the names of the special symbols
– [ ] brackets
– { } braces
– ( ) parentheses
– @ commercial ‘at’ sign
– & ampersand
– ~ tilde

29. 000 001 010 011 100 101 110 111
0000 NULL DLE 0 @ P ` p
0001 SOH DC1 ! 1 A Q a q
0010 STX DC2 " 2 B R b r
0011 ETX DC3 # 3 C S c s
0100 EDT DC4 $ 4 D T d t
0101 ENQ NAK % 5 E U e u
0110 ACK SYN & 6 F V f v
0111 BEL ETB ' 7 G W g w
1000 BS CAN ( 8 H X h x
1001 HT EM ) 9 I Y i y
1010 LF SUB * : J Z j z
1011 VT ESC + ; K [ k {
1100 FF FS , < L l |
1101 CR GS - = M ] m }
1110 SO RS . > N ^ n ~
1111 SI US / ? O _ o DEL

30. Escape Sequences
• Extend the capability of the ASCII code set
• For controlling terminals and formatting output
• Defined by ANSI in documents X3.41-1974 and
X3.64-1977
• The escape code is ESC = 1B16
• An escape sequence begins with two codes:
ESC [
1B16 5B16

31. Examples
• Erase display: ESC [ 2 J
• Erase line: ESC [ K

32. Next 1 slides
Standard Alphanumeric Formats
• BCD
• ASCII
• EBCDIC
• Unicode

33. EBCDIC
• Extended BCD Interchange Code
(pronounced ebb’-se-dick)
• 8-bit code
• Developed by IBM
• Rarely used today
• IBM mainframes only

34. Next 2 slides
Standard Alphanumeric Formats
• BCD
• ASCII
• EBCDIC
• Unicode

35. Unicode
• 16-bit standard
• Developed by a consortia
• Intended to supercede older 7- and 8-bit
codes

36. Unicode Version 2.1
• 1998
• Improves on version 2.0
• Includes the Euro sign (20AC16 = )
• From the standard:
…contains 38,887 distinct coded characters derived
from the supported scripts. These characters cover the
principal written languages of the Americas, Europe,
the Middle East, Africa, India, Asia, and Pacifica.
http://www.unicode.org

37. Keyboard Input
• Key (“scan”) codes are converted to ASCII
• ASCII code sent to host computer
• Received by the host as a “stream” of data
• Stored in buffer
• Processed
• Etc.
pp. 69

38. Shift Key
• inhibits bit 5 in the ASCII code
Key(s)
ASCII code
6 5 4 3 2 1 0 Character
1 1 0 0 0 0 1
1 0 0 0 0 0 1
a
A
a
aShift

39. Control Key
• inhibits bits 5 & 6 in the ASCII code
Key(s)
ASCII code
6 5 4 3 2 1 0 Character
1 1 0 0 0 1 1
0 0 0 0 0 1 1
c
ETX
c
cCtrl
Control
code

40. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

41. OCR
Hello, world
Page of text
Optical scan 10110110…
Computer file

42. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

43. Bar Codes
• An automatic identification (Auto ID)
technology that streamlines identification
and data collection
• See
http://www.digital.net/barcoder/barcode.html

44. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

45. Voice/audio Input
• Input device: microphone
• Audio input is “digitized” and stored
• Processed in two ways
– As is (no recognition)
– Recognized and converted to alphanumeric data
(ASCII)
Digitize 10110010…

46. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

47. Punched Cards
• Invented by Herman Hollerith (founder of
IBM)
• Each card holds 80 characters

48. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

49. Images
• Typically images are pictures that are
optically scanned and saved as a “bit map”
or in some other format
• Many formats
– gif, jpeg, …

50. Typical “Save As” Dialog

51. Objects
• Images made of geometrically definable
shapes
• Offer efficiency, flexibility, small size, etc.

52. Other Input
• OCR – optical character recognition
• Bar code readers
• Voice/audio input
• Punched cards
• Images / objects
• Pointing devices
pp. 69-86

53. Pointing Devices
• Originally used for specifying coordinates
(x, y) for graphical input
• Today used as general purpose device for
“graphical user interfaces” (GUIs)

54. Thank you