1. Faculty of Cybernetics, Statistics and Economic Informatics –
12/4/2018
IT Basics 4
Faculty of Cybernetics, Statistics and Economic Informatics –
BUES
Prof. Răzvan ZOTA, Ph.D.
4-Dec-18

2. Information coding in computers
Let’s have:
With these symbols we may construct n code words: C ={c1,c2,…,cn}
The code words are finite sequences of symbols from set A.
Coding represents the operation of stating a bi-univocal correspondence between the symbols xiX and ciC. The set of words ci (i=1..k ) are making a code.
Two type of words:
Words with sense
Words without sense
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3. Alphanumeric codes Examples:
12/4/2018
Alphanumeric codes
Examples:
EBCDIC (Extended Binary Coded Decimal Information Interchange)
ASCII (American Standard Code for Information Interchange)
Unicode – supports electronic data exchanges, text processing and displaying in several international languages. It has been adopted by great international companies, like: Apple, HP, IBM, Microsoft, Oracle, Sun, Unisys, etc.
Last version – 2016 – v9.0 (support for > characters)
For more info see:
In Version 8.0, the standard grew by 7,716 characters. This version continues the Unicode Consortium’s long-standing commitment to support the full diversity of languages around the world by adding new scripts and other characters that support additional languages of Africa and India, such as Ik, Kulango, and Tai Ahom. The text of the latest version also documents the newly adopted Georgian lari currency symbol.

4. 12/4/2018

5. Alphanumeric codes (cont.)
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6. Alphanumeric codes (cont.)
4-Dec-18

7. Numeric codes Weighted Non-weighted
Weighted codes (zi are the binary digits from 0 to 9) have the following characteristic: each digit has its associated weight and the value of the decimal number is computed by multiplying the code digit with the (associated) weight and summing the values:
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8. Weighted codes Decimal digit 8421 code 2421 code (Aiken) Code 50 43210
0000 1
0001
0111 2
0010
0110 3
0011
0101 4
0100 5
1011 6
1100
1010 7
1101
1001 8
1000
1110 9
1111
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9. Weighted codes (cont.) Decimal digit 4221 code 5421 code 7421 code
6421
0000 1
0001
0011 2
0010 3
0101 4
0110
0100 5
1001
1000
0111 6
1100 7
1101
1010
1011 8
1110 9
1111
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10. Weighted codes (cont.)
8421 code  Binary-decimal natural code, with weights powers of 2
2421 code (Aiken) – auto-complementary code
8421 code – the last two weights are negative, auto-complementary code
( ) code – sequences of 7 binary symbols divided into two groups
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11. Non-weighted codes Decimal digit Excess 3 code Gray code 2 of 5
(74 210)
0011
0000
11 000 1
0100
0001
00 011 2
0101
00 101 3
0110
0010
00 110 4
0111
01 001 5
1000
01 010 6
1001
01 100 7
1010
10 001 8
1011
1100
10 010 9
1101
10 100
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12. Non-weighted codes Exces 3 code – auto-complementary
Gray code – two consecutive code sequences differ by only one binary position
2 of 5 code – pseudo-weighted code; the code sequences for decimal digits 19 have the associated weights except digit 0. Only 2 from the 5 binary digits are significant (have the value of 1).
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13. Barcodes – an example
Barcode 2 of 5 (ITF, from Interleaved Two of Five) – two lines are wide and three are narrow.
The print rate between wide line/narrow line is 2:1 or 3:1.
The spaces do not contain information (the interleaved 2 of 5 code the information density is bigger because the spaces are containing information also)
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14. Barcodes - example
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15. Barcodes - example
Example: number 10 representation with 2 of 5 barcode
START 1
STOP
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16. QR (Quick Response) code
Represents a matrix (bi-dimensional) barcode
Example:
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