ASCII table. Letters are only a representation of numbers on our computer systems. The lowercase letter "A" for example is 97. This system is called ASCII.
Notes, control. We do not print "CONTROL" characters as they are displayed as strange characters. In HTML files it is usually best to use simple characters when possible.
In a sense, the letter "A" is not "A" but is rather 97. With ASCII numbers we can test ranges of characters fast and easily. With Python we can output an ASCII table.
0 CONTROL
1 CONTROL
2 CONTROL
3 CONTROL
4 CONTROL
5 CONTROL
6 CONTROL
7 CONTROL
8 CONTROL
9 WHITESPACE
10 WHITESPACE
11 WHITESPACE
12 WHITESPACE
13 WHITESPACE
14 CONTROL
15 CONTROL
16 CONTROL
17 CONTROL
18 CONTROL
19 CONTROL
20 CONTROL
21 CONTROL
22 CONTROL
23 CONTROL
24 CONTROL
25 CONTROL
26 CONTROL
27 CONTROL
28 CONTROL
29 CONTROL
30 CONTROL
31 CONTROL
32 WHITESPACE
33 ! PUNCTUATION
34 " PUNCTUATION
35 # PUNCTUATION
36 $ PUNCTUATION
37 % PUNCTUATION
38 & PUNCTUATION
39 ' PUNCTUATION
40 ( PUNCTUATION
41 ) PUNCTUATION
42 * PUNCTUATION
43 + PUNCTUATION
44 , PUNCTUATION
45 - PUNCTUATION
46 . PUNCTUATION
47 / PUNCTUATION
48 0 DIGIT
49 1 DIGIT
50 2 DIGIT
51 3 DIGIT
52 4 DIGIT
53 5 DIGIT
54 6 DIGIT
55 7 DIGIT
56 8 DIGIT
57 9 DIGIT
58 : PUNCTUATION
59 ; PUNCTUATION
60 < PUNCTUATION
61 = PUNCTUATION
62 > PUNCTUATION
63 ? PUNCTUATION
64 @ PUNCTUATION
65 A ASCII_LETTER
66 B ASCII_LETTER
67 C ASCII_LETTER
68 D ASCII_LETTER
69 E ASCII_LETTER
70 F ASCII_LETTER
71 G ASCII_LETTER
72 H ASCII_LETTER
73 I ASCII_LETTER
74 J ASCII_LETTER
75 K ASCII_LETTER
76 L ASCII_LETTER
77 M ASCII_LETTER
78 N ASCII_LETTER
79 O ASCII_LETTER
80 P ASCII_LETTER
81 Q ASCII_LETTER
82 R ASCII_LETTER
83 S ASCII_LETTER
84 T ASCII_LETTER
85 U ASCII_LETTER
86 . ASCII_LETTER
87 . ASCII_LETTER
88 . ASCII_LETTER
89 . ASCII_LETTER
90 Z ASCII_LETTER
91 [ PUNCTUATION
92 \ PUNCTUATION
93 ] PUNCTUATION
94 ^ PUNCTUATION
95 _ PUNCTUATION
96 ` PUNCTUATION
97 a ASCII_LETTER
98 b ASCII_LETTER
99 c ASCII_LETTER
100 d ASCII_LETTER
101 e ASCII_LETTER
102 f ASCII_LETTER
103 g ASCII_LETTER
104 h ASCII_LETTER
105 i ASCII_LETTER
106 . ASCII_LETTER
107 . ASCII_LETTER
108 . ASCII_LETTER
109 . ASCII_LETTER
110 . ASCII_LETTER
111 . ASCII_LETTER
112 . ASCII_LETTER
113 . ASCII_LETTER
114 . ASCII_LETTER
115 . ASCII_LETTER
116 . ASCII_LETTER
117 . ASCII_LETTER
118 . ASCII_LETTER
119 . ASCII_LETTER
120 . ASCII_LETTER
121 . ASCII_LETTER
122 z ASCII_LETTER
123 { PUNCTUATION
124 | PUNCTUATION
125 } PUNCTUATION
126 ~ PUNCTUATION
127 CONTROL
Example program. To begin we loop over the first 128 numbers from 0 to 127 inclusive. We convert each integer to a 1-character string with chr.
Then We test the value of the string against constant string literals in the string module.
Tip If a string is founding ascii_letters we can print its classification as well as its value.
Note The classification logic here is not strictly required for an ASCII table, but it helps for readability.
import string
for i in range(128):
string_value = chr(i)
# Test string value against constant strings.
if string_value in string.whitespace:
print(i, "WHITESPACE")
elif string_value in string.ascii_letters:
print(i, string_value, "ASCII_LETTER")
elif string_value in string.punctuation:
print(i, string_value, "PUNCTUATION")
elif string_value in string.digits:
print(i, string_value, "DIGIT")
else:
# Assume others are control characters.
print(i, "CONTROL")
Notes, strings versus ints. Suppose you have a one-character string. This requires more effort to store and handle than an int, which usually requires just 4 bytes.
And An int can be modified with increment, decrement and other numeric operations. So a char can be quickly modified.
A summary. ASCII is an important concept in computer programs. Strings are not a low-level data type. But ints, which indicate ASCII characters, are. This is key to many optimizations.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Sep 25, 2022 (edit).