TL;DR

ASCII is a standardized character encoding system created in the 1960s to represent English alphabets, numbers, and basic formatting, originally consisting of 128 characters. It was later extended to 256 characters to accommodate other languages, but its limitations led to the development of more comprehensive encoding systems like Unicode and UTF-8.

What is ASCII?

Computers speak in binary (zeros and ones). Many moons ago, we needed computers to interpret and store English alphabets, numbers, and basic formatting. Before ASCII, computer systems used different encoding schemes, which resulted in compatibility issues.

ASCII (American Standard Code for Information Interchange) was made in the early 1960s and officially standardized in 1963. It was created by a group led by Robert W. Bemer, who is known as the "father of ASCII." They wanted a standard way for different computers and devices to share information.

The original ASCII standard was a 7-bit encoding which represented 128 characters. This included 95 printable characters: numbers, English alphabets (both lower and upper case), punctuation marks, special symbols, and 33 control characters (newline, carriage return, tab etc.).

Original ASCII character set:

ASCII Code	Character	Description	Category
0	NUL	Null	Control
1	SOH	Start of Header	Control
2	STX	Start of Text	Control
3	ETX	End of Text	Control
4	EOT	End of Transmission	Control
5	ENQ	Enquiry	Control
6	ACK	Acknowledge	Control
7	BEL	Bell	Control
8	BS	Backspace	Control
9	TAB	Horizontal Tabulation	Control
10	LF	Line Feed	Control
11	VT	Vertical Tabulation	Control
12	FF	Form Feed	Control
13	CR	Carriage Return	Control
14	SO	Shift Out	Control
15	SI	Shift In	Control
16	DLE	Data Link Escape	Control
17	DC1	Device Control 1 (XON)	Control
18	DC2	Device Control 2	Control
19	DC3	Device Control 3 (XOFF)	Control
20	DC4	Device Control 4	Control
21	NAK	Negative Acknowledge	Control
22	SYN	Synchronous Idle	Control
23	ETB	End of Transmission Block	Control
24	CAN	Cancel	Control
25	EM	End of Medium	Control
26	SUB	Substitute	Control
27	ESC	Escape	Control
28	FS	File Separator	Control
29	GS	Group Separator	Control
30	RS	Record Separator	Control
31	US	Unit Separator	Control
32	(space)	Space	Printable
33	!	Exclamation Mark	Printable
34	"	Double Quotation Mark	Printable
35	#	Number Sign	Printable
36	$	Dollar Sign	Printable
37	%	Percent Sign	Printable
38	&	Ampersand	Printable
39	'	Apostrophe	Printable
40	(	Left Parenthesis	Printable
41	)	Right Parenthesis	Printable
42	*	Asterisk	Printable
43	+	Plus Sign	Printable
44	,	Comma	Printable
45	-	Hyphen-Minus	Printable
46	.	Period	Printable
47	/	Slash	Printable
48	0	Digit Zero	Printable
49	1	Digit One	Printable
50	2	Digit Two	Printable
51	3	Digit Three	Printable
52	4	Digit Four	Printable
53	5	Digit Five	Printable
54	6	Digit Six	Printable
55	7	Digit Seven	Printable
56	8	Digit Eight	Printable
57	9	Digit Nine	Printable
58	:	Colon	Printable
59	;	Semicolon	Printable
60	<	Less Than Sign	Printable
61	\=	Equals Sign	Printable
62	\>	Greater Than Sign	Printable
63	?	Question Mark	Printable
64	@	At Sign	Printable
65	A	Capital Letter A	Printable
66	B	Capital Letter B	Printable
67	C	Capital Letter C	Printable
68	D	Capital Letter D	Printable
69	E	Capital Letter E	Printable
70	F	Capital Letter F	Printable
71	G	Capital Letter G	Printable
72	H	Capital Letter H	Printable
73	I	Capital Letter I	Printable
74	J	Capital Letter J	Printable
75	K	Capital Letter K	Printable
76	L	Capital Letter L	Printable
77	M	Capital Letter M	Printable
78	N	Capital Letter N	Printable
79	O	Capital Letter O	Printable
80	P	Capital Letter P	Printable
81	Q	Capital Letter Q	Printable
82	R	Capital Letter R	Printable
83	S	Capital Letter S	Printable
84	T	Capital Letter T	Printable
85	U	Capital Letter U	Printable
86	V	Capital Letter V	Printable
87	W	Capital Letter W	Printable
88	X	Capital Letter X	Printable
89	Y	Capital Letter Y	Printable
90	Z	Capital Letter Z	Printable
91	[	Left Square Bracket	Printable
92	\	Backslash	Printable
93	]	Right Square Bracket	Printable
94	^	Circumflex Accent	Printable
95	_	Underscore	Printable
96	`	Grave Accent	Printable
97	a	Lowercase Letter a	Printable
98	b	Lowercase Letter b	Printable
99	c	Lowercase Letter c	Printable
100	d	Lowercase Letter d	Printable
101	e	Lowercase Letter e	Printable
102	f	Lowercase Letter f	Printable
103	g	Lowercase Letter g	Printable
104	h	Lowercase Letter h	Printable
105	i	Lowercase Letter i	Printable
106	j	Lowercase Letter j	Printable
107	k	Lowercase Letter k	Printable
108	l	Lowercase Letter l	Printable
109	m	Lowercase Letter m	Printable
110	n	Lowercase Letter n	Printable
111	o	Lowercase Letter o	Printable
112	p	Lowercase Letter p	Printable
113	q	Lowercase Letter q	Printable
114	r	Lowercase Letter r	Printable
115	s	Lowercase Letter s	Printable
116	t	Lowercase Letter t	Printable
117	u	Lowercase Letter u	Printable
118	v	Lowercase Letter v	Printable
119	w	Lowercase Letter w	Printable
120	x	Lowercase Letter x	Printable
121	y	Lowercase Letter y	Printable
122	z	Lowercase Letter z	Printable
123	{	Left Curly Brace	Printable
124			Vertical Line	Printable
125	}	Right Curly Brace	Printable
126	~	Tilde	Printable
127	DEL	Delete	Control

Pro Tip: Use ASCII to test if a character is uppercase or lowercase.

https://replit.com/@ryan-syed/ASCIIUpperAndLower

Extended ASCII character set:

As computing expanded globally, the ASCII character set was later extended to accommodate Western European languages and other country-specific variations which made it grow to 256 characters using the 8 unused bit. However, even with this extension it was limited in scope and didn't provide comprehensive support for all languages.

ASCII Code	Character	Description
128	Ç	Latin Capital Letter C-cedilla
129	ü	Latin Small Letter U with diaeresis
130	é	Latin Small Letter E with acute
131	â	Latin Small Letter A with circumflex
132	ä	Latin Small Letter A with diaeresis
133	à	Latin Small Letter A with grave
134	å	Latin Small Letter A with ring above
135	ç	Latin Small Letter C-cedilla
136	ê	Latin Small Letter E with circumflex
137	ë	Latin Small Letter E with diaeresis
138	è	Latin Small Letter E with grave
139	ï	Latin Small Letter I with diaeresis
140	î	Latin Small Letter I with circumflex
141	ì	Latin Small Letter I with grave
142	Ä	Latin Capital Letter A with diaeresis
143	Å	Latin Capital Letter A with ring above
144	É	Latin Capital Letter E with acute
145	æ	Latin Small Ligature AE
146	Æ	Latin Capital Ligature AE
147	ô	Latin Small Letter O with circumflex
148	ö	Latin Small Letter O with diaeresis
149	ò	Latin Small Letter O with grave
150	û	Latin Small Letter U with circumflex
151	ù	Latin Small Letter U with grave
152	ÿ	Latin Small Letter Y with diaeresis
153	Ö	Latin Capital Letter O with diaeresis
154	Ü	Latin Capital Letter U with diaeresis
155	ø	Latin Small Letter O with stroke
156	£	Pound Sign
157	Ø	Latin Capital Letter O with stroke
158	×	Multiplication Sign
159	ƒ	Latin Small Letter F with hook
160	á	Latin Small Letter A with acute
161	í	Latin Small Letter I with acute
162	ó	Latin Small Letter O with acute
163	ú	Latin Small Letter U with acute
164	ñ	Latin Small Letter N with tilde
165	Ñ	Latin Capital Letter N with tilde
166	ª	Feminine Ordinal Indicator
167	º	Masculine Ordinal Indicator
168	¿	Inverted Question Mark
169	®	Registered Sign
170	¬	Not Sign
171	½	Vulgar Fraction One Half
172	¼	Vulgar Fraction One Quarter
173	¡	Inverted Exclamation Mark
174	«	Left-Pointing Double Angle Quotation Mark
175	»	Right-Pointing Double Angle Quotation Mark
176	░	Light Shade
177	▒	Medium Shade
178	▓	Dark Shade
179	│	Box Drawings Light Vertical
180	┤	Box Drawings Light Vertical and Left
181	╡	Box Drawings Vertical Single and Left Double
182	╢	Box Drawings Vertical Double and Left Single
183	╖	Box Drawings Down Double and Left Single
184	╕	Box Drawings Down Single and Left Double
185	╣	Box Drawings Double Vertical and Left
186	║	Box Drawings Double Vertical
187	╗	Box Drawings Double Down and Left
188	╝	Box Drawings Double Up and Left
189	╜	Box Drawings Up Double and Left Single
190	╛	Box Drawings Up Single and Left Double
191	┐	Box Drawings Light Down and Left
192	└	Box Drawings Light Up and Right
193	┴	Box Drawings Light Up and Horizontal
194	┬	Box Drawings Light Down and Horizontal
195	├	Box Drawings Light Vertical and Right
196	─	Box Drawings Light Horizontal
197	┼	Box Drawings Light Vertical and Horizontal
198	╞	Box Drawings Vertical Single and Right Double
199	╟	Box Drawings Vertical Double and Right Single
200	╚	Box Drawings Double Up and Right
201	╔	Box Drawings Double Down and Right
202	╩	Box Drawings Double Up and Horizontal
203	╦	Box Drawings Double Down and Horizontal
204	╠	Box Drawings Double Vertical and Right
205	═	Box Drawings Double Horizontal
206	╬	Box Drawings Double Vertical and Horizontal
207	╧	Box Drawings Up Single and Right Double
208	╨	Box Drawings Up Double and Right Single
209	╤	Box Drawings Down Single and Right Double
210	╥	Box Drawings Down Double and Right Single
211	╙	Box Drawings Up Double and Horizontal Single
212	╘	Box Drawings Up Single and Horizontal Double
213	╒	Box Drawings Down Single and Horizontal Double
214	╓	Box Drawings Down Double and Horizontal Single
215	╫	Box Drawings Vertical Double and Horizontal Single
216	╪	Box Drawings Vertical Single and Horizontal Double
217	┘	Box Drawings Light Up and Left
218	┌	Box Drawings Light Down and Right
219	█	Full Block
220	▄	Lower Half Block
221	▌	Left Half Block
222	▐	Right Half Block
223	▀	Upper Half Block
224	α	Greek Small Letter Alpha
225	ß	Latin Small Letter Sharp S
226	Γ	Greek Capital Letter Gamma
227	π	Greek Small Letter Pi
228	Σ	Greek Capital Letter Sigma
229	σ	Greek Small Letter Sigma
230	µ	Micro Sign
231	τ	Greek Small Letter Tau
232	Φ	Greek Capital Letter Phi
233	Θ	Greek Capital Letter Theta
234	Ω	Greek Capital Letter Omega
235	δ	Greek Small Letter Delta
236	∞	Infinity
237	φ	Greek Small Letter Phi
238	ε	Greek Small Letter Epsilon
239	∩	Intersection
240	≡	Identical to
241	±	Plus-Minus Sign
242	≥	Greater Than or Equal To
243	≤	Less Than or Equal To
244	⌠	Top Half Integral
245	⌡	Bottom Half Integral
246	÷	Division Sign
247	≈	Almost Equal to
248	°	Degree Sign
249	∙	Bullet
250	·	Middle Dot
251	√	Square Root
252	ⁿ	Superscript Latin Small Letter N
253	²	Superscript Two
254	■	Black Square
255		No-Break Space
256		Non-Standard Character

As computers got better and people needed more languages, ASCII's limited set of characters wasn't enough. So, bigger systems like ISO 8859-1 and UTF-8 were made to show characters from many languages

ASCII played a crucial role in standardizing character encoding for early computing systems, facilitating communication between different devices. Despite its limitations and the development of more comprehensive encoding systems like Unicode and UTF-8, ASCII remains an essential part of the history of computing and continues to be used in various applications today.

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ASCII Explained: What You Need to Know

A Beginner's Overview of ASCII Essentials

Table of contents

TL;DR

What is ASCII?

Original ASCII character set:

Pro Tip: Use ASCII to test if a character is uppercase or lowercase.

Extended ASCII character set: