Character coding schemes

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Presentation transcript:

Character coding schemes Highcliffe School ICT Department

Intro How do we store text in computer memory? We use coding schemes. ASCII UNICODE

Intro How do we store text in computer memory? We use coding schemes. ASCII UNICODE

128 Characters A = 65 1000001 7 Bits ASCII UNICODE

128 Characters A = 65 1000001 ASCII 7 Bits UNICODE

A = 65 1000001 ASCII 7 Bits 128 Characters UNICODE

ASCII 7 Bits 128 Characters UNICODE A = 65 1000001

?1000001 Error Checking other characters UNICODE ASCII 7 Bits 128 Characters A = 65

?1000001 Error Checking other characters UNICODE ASCII 7 Bits 128 Characters A = 65

A 65 1000001 B 66 1000010 C 67 1000011 a 97 1100010 b 98 1100011

A 65 1000001 00110100 00111000 B 66 1000010 C 67 1000011 48 ERROR CHECKING a 97 1100010 00000000 00110000 b 98 1100011

ASCII Characters 00110100 00111000 48 ERROR CHECKING 00000000 00110000 65 1000001 00110100 00111000 B 66 1000010 C 67 1000011 48 ERROR CHECKING a 97 1100010 00000000 00110000 b 98 1100011 Number -16 Bit Word

ASCII Characters 00110100 00111000 52 56 ERROR CHECKING 4 8 48 65 1000001 00110100 00111000 B 66 1000010 52 56 C 67 1000011 ERROR CHECKING 4 8 a 97 1100010 48 00000000 00110000 b 98 1100011 Number -16 Bit Word

A 65 1000001 00110100 00111000 B 66 1000010 C 67 1000011 ERROR CHECKING 48 a 97 1100010 00000000 00110000 b 98 1100011

ERROR CHECKING 00110100 00111000 Even Parity Total 1 Bits = even 48 65 1000001 00110100 00111000 B 66 1000010 Even Parity Total 1 Bits = even C 67 1000011 48 _1100110 Odd Parity Total 0 Bits = odd a 97 1100010 00000000 00110000 b 98 1100011 _1100110

ERROR CHECKING 00110100 00111000 Majority Vote Even Parity 65 1000001 00110100 00111000 B 66 1000010 Majority Vote Even Parity Total 1 Bits = even C 67 1000011 0 1 0 1 1 1 0 1 48 _1100110 000 111 000 111 111 111 000 111 a 97 1100010 Odd Parity Total 0 Bits = odd 00000000 00110000 010 110 100 110 011 101 000 011 b 98 1100011 _1100110

Hamming code - transmitting Bit Position 11 10 9 8 7 6 5 4 3 2 1 Date/Parity D P4 P3 P2 P1 Data Code Sent

Hamming code - DECODING Bit Position 11 10 9 8 7 6 5 4 3 2 1 Date/Parity D P4 P3 P2 P1 Code Flip Data