Alphanumeric codes are used to represent different data, letters, and numbers by distinguishing symbols and characters.
There are three types of alphanumeric codes: ASCII code, EBCDIC code, and Unicode. ASCII Code is the most commonly used of these (although the others are used in specific situations).
What is ASCII code
ASCII stands for ‘American Standard Code for Information Interchange’, and is pronounced as ‘ask-ee’. ASCII code is used to represent alphanumeric data in computers, communication equipment, and electronic devices in a more scientific manner. ASCII code was first published as a standard in 1967. From then it is constantly being updated and revised. In 1986 the latest version was called and published as ANSI X3.4.
ASCII code is a 7 bit code and is hence able to represent 27 = 128 characters. Currently, a total number of 95 printable characters are represented by this code including 26 upper case letters (A – Z), 26 lower case letters (a – z), 10 numerals (0 – 9), and 33 special characters which include mathematical symbols, punctuation marks and space characters.
The latest development in the field of ASCII code is the development of 8 bit code – which is known as US ASCII-8 or ASCII-8. As it is an 8 bit code, it can represent 28 = 256 characters. The tabulated form of the ASCII code is given below.
ASCII Code Table
DEC | OCT | HEX | BIN | Symbol | Description |
0 | 0 | 0 | 0 | NUL | Null char |
1 | 1 | 1 | 1 | SOH | Start of Heading |
2 | 2 | 2 | 10 | STX | Start of Text |
3 | 3 | 3 | 11 | ETX | End of Text |
4 | 4 | 4 | 100 | EOT | End of Transmission |
5 | 5 | 5 | 101 | ENQ | Enquiry |
6 | 6 | 6 | 110 | ACK | Acknowledgment |
7 | 7 | 7 | 111 | BEL | Bell |
8 | 10 | 8 | 1000 | BS | Back Space |
9 | 11 | 9 | 1001 | HT | Horizontal Tab |
10 | 12 | 0A | 1010 | LF | Line Feed |
11 | 13 | 0B | 1011 | VT | Vertical Tab |
12 | 14 | 0C | 1100 | FF | Form Feed |
13 | 15 | 0D | 1101 | CR | Carriage Return |
14 | 16 | 0E | 1110 | SO | Shift Out / X-On |
15 | 17 | 0F | 1111 | SI | Shift In / X-Off |
16 | 20 | 10 | 10000 | DLE | Data Line Escape |
17 | 21 | 11 | 10001 | DC1 | Device Control 1 (oft. XON) |
18 | 22 | 12 | 10010 | DC2 | Device Control 2 |
19 | 23 | 13 | 10011 | DC3 | Device Control 3 (oft. XOFF) |
20 | 24 | 14 | 10100 | DC4 | Device Control 4 |
21 | 25 | 15 | 10101 | NAK | Negative Acknowledgement |
22 | 26 | 16 | 10110 | SYN | Synchronous Idle |
23 | 27 | 17 | 10111 | ETB | End of Transmit Block |
24 | 30 | 18 | 11000 | CAN | Cancel |
25 | 31 | 19 | 11001 | EM | End of Medium |
26 | 32 | 1A | 11010 | SUB | Substitute |
27 | 33 | 1B | 11011 | ESC | Escape |
28 | 34 | 1C | 11100 | FS | File Separator |
29 | 35 | 1D | 11101 | GS | Group Separator |
30 | 36 | 1E | 11110 | RS | Record Separator |
31 | 37 | 1F | 11111 | US | Unit Separator |
32 | 40 | 20 | 100000 | Space | |
33 | 41 | 21 | 100001 | ! | Exclamation mark |
34 | 42 | 22 | 100010 | “ | Double quotes (or speech marks) |
35 | 43 | 23 | 100011 | # | Number |
36 | 44 | 24 | 100100 | $ | Dollar |
37 | 45 | 25 | 100101 | % | Procenttecken |
38 | 46 | 26 | 100110 | & | Ampersand |
39 | 47 | 27 | 100111 | ‘ | Single quote |
40 | 50 | 28 | 101000 | ( | Open parenthesis (or open bracket) |
41 | 51 | 29 | 101001 | ) | Close parenthesis (or close bracket) |
42 | 52 | 2A | 101010 | * | Asterisk |
43 | 53 | 2B | 101011 | + | Plus |
44 | 54 | 2C | 101100 | , | Comma |
45 | 55 | 2D | 101101 | – | Hyphen |
46 | 56 | 2E | 101110 | . | Period, dot or full stop |
47 | 57 | 2F | 101111 | / | Slash or divide |
48 | 60 | 30 | 110000 | 0 | Zero |
49 | 61 | 31 | 110001 | 1 | One |
50 | 62 | 32 | 110010 | 2 | Two |
51 | 63 | 33 | 110011 | 3 | Three |
52 | 64 | 34 | 110100 | 4 | Four |
53 | 65 | 35 | 110101 | 5 | Five |
54 | 66 | 36 | 110110 | 6 | Six |
55 | 67 | 37 | 110111 | 7 | Seven |
56 | 70 | 38 | 111000 | 8 | Eight |
57 | 71 | 39 | 111001 | 9 | Nine |
58 | 72 | 3A | 111010 | : | Colon |
59 | 73 | 3B | 111011 | ; | Semicolon |
60 | 74 | 3C | 111100 | < | Less than (or open angled bracket) |
61 | 75 | 3D | 111101 | = | Equals |
62 | 76 | 3E | 111110 | > | Greater than (or close angled bracket) |
63 | 77 | 3F | 111111 | ? | Question mark |
64 | 100 | 40 | 1000000 | @ | At symbol |
65 | 101 | 41 | 1000001 | A | Uppercase A |
66 | 102 | 42 | 1000010 | B | Uppercase B |
67 | 103 | 43 | 1000011 | C | Uppercase C |
68 | 104 | 44 | 1000100 | D | Uppercase D |
69 | 105 | 45 | 1000101 | E | Uppercase E |
70 | 106 | 46 | 1000110 | F | Uppercase F |
71 | 107 | 47 | 1000111 | G | Uppercase G |
72 | 110 | 48 | 1001000 | H | Uppercase H |
73 | 111 | 49 | 1001001 | I | Uppercase I |
74 | 112 | 4A | 1001010 | J | Uppercase J |
75 | 113 | 4B | 1001011 | K | Uppercase K |
76 | 114 | 4C | 1001100 | L | Uppercase L |
77 | 115 | 4D | 1001101 | M | Uppercase M |
78 | 116 | 4E | 1001110 | N | Uppercase N |
79 | 117 | 4F | 1001111 | O | Uppercase O |
80 | 120 | 50 | 1010000 | P | Uppercase P |
81 | 121 | 51 | 1010001 | Q | Uppercase Q |
82 | 122 | 52 | 1010010 | R | Uppercase R |
83 | 123 | 53 | 1010011 | S | Uppercase S |
84 | 124 | 54 | 1010100 | T | Uppercase T |
85 | 125 | 55 | 1010101 | U | Uppercase U |
86 | 126 | 56 | 1010110 | V | Uppercase V |
87 | 127 | 57 | 1010111 | W | Uppercase W |
88 | 130 | 58 | 1011000 | X | Uppercase X |
89 | 131 | 59 | 1011001 | Y | Uppercase Y |
90 | 132 | 5A | 1011010 | Z | Uppercase Z |
91 | 133 | 5B | 1011011 | [ | Opening bracket |
92 | 134 | 5C | 1011100 | \ | Backslash |
93 | 135 | 5D | 1011101 | ] | Closing bracket |
94 | 136 | 5E | 1011110 | ^ | Caret – circumflex |
95 | 137 | 5F | 1011111 | _ | Underscore |
96 | 140 | 60 | 1100000 | ` | Grave accent |
97 | 141 | 61 | 1100001 | a | Lowercase a |
98 | 142 | 62 | 1100010 | b | Lowercase b |
99 | 143 | 63 | 1100011 | c | Lowercase c |
100 | 144 | 64 | 1100100 | d | Lowercase d |
101 | 145 | 65 | 1100101 | e | Lowercase e |
102 | 146 | 66 | 1100110 | f | Lowercase f |
103 | 147 | 67 | 1100111 | g | Lowercase g |
104 | 150 | 68 | 1101000 | h | Lowercase h |
105 | 151 | 69 | 1101001 | i | Lowercase i |
106 | 152 | 6A | 1101010 | j | Lowercase j |
107 | 153 | 6B | 1101011 | k | Lowercase k |
108 | 154 | 6C | 1101100 | l | Lowercase l |
109 | 155 | 6D | 1101101 | m | Lowercase m |
110 | 156 | 6E | 1101110 | n | Lowercase n |
111 | 157 | 6F | 1101111 | o | Lowercase o |
112 | 160 | 70 | 1110000 | p | Lowercase p |
113 | 161 | 71 | 1110001 | q | Lowercase q |
114 | 162 | 72 | 1110010 | r | Lowercase r |
115 | 163 | 73 | 1110011 | s | Lowercase s |
116 | 164 | 74 | 1110100 | t | Lowercase t |
117 | 165 | 75 | 1110101 | u | Lowercase u |
118 | 166 | 76 | 1110110 | v | Lowercase v |
119 | 167 | 77 | 1110111 | w | Lowercase w |
120 | 170 | 78 | 1111000 | x | Lowercase x |
121 | 171 | 79 | 1111001 | y | Lowercase y |
122 | 172 | 7A | 1111010 | z | Lowercase z |
123 | 173 | 7B | 1111011 | { | Opening brace |
124 | 174 | 7C | 1111100 | | | Vertical bar |
125 | 175 | 7D | 1111101 | } | Closing brace |
126 | 176 | 7E | 1111110 | ~ | Equivalency sign – tilde |
127 | 177 | 7F | 1111111 | Delete |
From the table we can see that numbers 0 – 9 are represented with binary values with prefix 0011. In a similar fashion in case of upper-case letters -‘P’ to ‘Z’ are represented by 0101 0000 to 0101 1010, lower-case letters ‘p’ to ‘z’ are represented by 0111 0000 to 0111 1010.