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ASCII Table Reference

Introduction

In string manipulation and array mapping problems, converting characters to their ASCII integer values (and vice-versa) is a highly common pattern.

In Python, use ord(char) to get the integer value, and chr(int) to get the character.

The Critical Offsets to Memorize

You do not need to memorize the entire ASCII table for an interview. You only need to memorize three numbers:

  • 'A' = 65
  • 'a' = 97
  • '0' = 48

Common Patterns

1. Finding the index for a character frequency array (0-25) 

# For lowercase letters
index = ord(char) - ord('a')

# For uppercase letters
index = ord(char) - ord('A')

2. Converting a digit character to an integer 

val = ord(char) - ord('0')

3. Toggling Case (Advanced Bitwise) The difference between 'a' (97) and 'A' (65) is exactly 32. In binary, 32 is 00100000. You can toggle case using bitwise XOR: 

# Uppercase to Lowercase
new_char = chr(ord('A') ^ 32) # 'a'

The Complete ASCII Reference

Char Dec Hex Char Dec Hex Char Dec Hex Char Dec Hex
NUL 0 00 Space 32 20 @ 64 40 ` 96 60
SOH 1 01 ! 33 21 A 65 41 a 97 61
STX 2 02 " 34 22 B 66 42 b 98 62
ETX 3 03 # 35 23 C 67 43 c 99 63
EOT 4 04 $ 36 24 D 68 44 d 100 64
ENQ 5 05 % 37 25 E 69 45 e 101 65
ACK 6 06 & 38 26 F 70 46 f 102 66
BEL 7 07 ' 39 27 G 71 47 g 103 67
BS 8 08 ( 40 28 H 72 48 h 104 68
TAB 9 09 ) 41 29 I 73 49 i 105 69
LF 10 0A * 42 2A J 74 4A j 106 6A
VT 11 0B + 43 2B K 75 4B k 107 6B
FF 12 0C , 44 2C L 76 4C l 108 6C
CR 13 0D - 45 2D M 77 4D m 109 6D
SO 14 0E . 46 2E N 78 4E n 110 6E
SI 15 0F / 47 2F O 79 4F o 111 6F
DLE 16 10 0 48 30 P 80 50 p 112 70
DC1 17 11 1 49 31 Q 81 51 q 113 71
DC2 18 12 2 50 32 R 82 52 r 114 72
DC3 19 13 3 51 33 S 83 53 s 115 73
DC4 20 14 4 52 34 T 84 54 t 116 74
NAK 21 15 5 53 35 U 85 55 u 117 75
SYN 22 16 6 54 36 V 86 56 v 118 76
ETB 23 17 7 55 37 W 87 57 w 119 77
CAN 24 18 8 56 38 X 88 58 x 120 78
EM 25 19 9 57 39 Y 89 59 y 121 79
SUB 26 1A : 58 3A Z 90 5A z 122 7A
ESC 27 1B ; 59 3B [ 91 5B { 123 7B
FS 28 1C < 60 3C \ 92 5C | 124 7C
GS 29 1D = 61 3D ] 93 5D } 125 7D
RS 30 1E > 62 3E ^ 94 5E ~ 126 7E
US 31 1F ? 63 3F _ 95 5F DEL 127 7F