ASCII Explained: What You Need to Know

ASCII Explained: What You Need to Know

A Beginner's Overview of ASCII Essentials

Aug 5, 2023·

14 min read


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 CodeCharacterDescriptionCategory
1SOHStart of HeaderControl
2STXStart of TextControl
3ETXEnd of TextControl
4EOTEnd of TransmissionControl
9TABHorizontal TabulationControl
10LFLine FeedControl
11VTVertical TabulationControl
12FFForm FeedControl
13CRCarriage ReturnControl
14SOShift OutControl
15SIShift InControl
16DLEData Link EscapeControl
17DC1Device Control 1 (XON)Control
18DC2Device Control 2Control
19DC3Device Control 3 (XOFF)Control
20DC4Device Control 4Control
21NAKNegative AcknowledgeControl
22SYNSynchronous IdleControl
23ETBEnd of Transmission BlockControl
25EMEnd of MediumControl
28FSFile SeparatorControl
29GSGroup SeparatorControl
30RSRecord SeparatorControl
31USUnit SeparatorControl
33!Exclamation MarkPrintable
34"Double Quotation MarkPrintable
35#Number SignPrintable
36$Dollar SignPrintable
37%Percent SignPrintable
40(Left ParenthesisPrintable
41)Right ParenthesisPrintable
43+Plus SignPrintable
480Digit ZeroPrintable
491Digit OnePrintable
502Digit TwoPrintable
513Digit ThreePrintable
524Digit FourPrintable
535Digit FivePrintable
546Digit SixPrintable
557Digit SevenPrintable
568Digit EightPrintable
579Digit NinePrintable
60<Less Than SignPrintable
61\=Equals SignPrintable
62\>Greater Than SignPrintable
63?Question MarkPrintable
64@At SignPrintable
65ACapital Letter APrintable
66BCapital Letter BPrintable
67CCapital Letter CPrintable
68DCapital Letter DPrintable
69ECapital Letter EPrintable
70FCapital Letter FPrintable
71GCapital Letter GPrintable
72HCapital Letter HPrintable
73ICapital Letter IPrintable
74JCapital Letter JPrintable
75KCapital Letter KPrintable
76LCapital Letter LPrintable
77MCapital Letter MPrintable
78NCapital Letter NPrintable
79OCapital Letter OPrintable
80PCapital Letter PPrintable
81QCapital Letter QPrintable
82RCapital Letter RPrintable
83SCapital Letter SPrintable
84TCapital Letter TPrintable
85UCapital Letter UPrintable
86VCapital Letter VPrintable
87WCapital Letter WPrintable
88XCapital Letter XPrintable
89YCapital Letter YPrintable
90ZCapital Letter ZPrintable
91[Left Square BracketPrintable
93]Right Square BracketPrintable
94^Circumflex AccentPrintable
96`Grave AccentPrintable
97aLowercase Letter aPrintable
98bLowercase Letter bPrintable
99cLowercase Letter cPrintable
100dLowercase Letter dPrintable
101eLowercase Letter ePrintable
102fLowercase Letter fPrintable
103gLowercase Letter gPrintable
104hLowercase Letter hPrintable
105iLowercase Letter iPrintable
106jLowercase Letter jPrintable
107kLowercase Letter kPrintable
108lLowercase Letter lPrintable
109mLowercase Letter mPrintable
110nLowercase Letter nPrintable
111oLowercase Letter oPrintable
112pLowercase Letter pPrintable
113qLowercase Letter qPrintable
114rLowercase Letter rPrintable
115sLowercase Letter sPrintable
116tLowercase Letter tPrintable
117uLowercase Letter uPrintable
118vLowercase Letter vPrintable
119wLowercase Letter wPrintable
120xLowercase Letter xPrintable
121yLowercase Letter yPrintable
122zLowercase Letter zPrintable
123{Left Curly BracePrintable
124Vertical LinePrintable
125}Right Curly BracePrintable

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

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 CodeCharacterDescription
128ÇLatin Capital Letter C-cedilla
129üLatin Small Letter U with diaeresis
130éLatin Small Letter E with acute
131âLatin Small Letter A with circumflex
132äLatin Small Letter A with diaeresis
133àLatin Small Letter A with grave
134åLatin Small Letter A with ring above
135çLatin Small Letter C-cedilla
136êLatin Small Letter E with circumflex
137ëLatin Small Letter E with diaeresis
138èLatin Small Letter E with grave
139ïLatin Small Letter I with diaeresis
140îLatin Small Letter I with circumflex
141ìLatin Small Letter I with grave
142ÄLatin Capital Letter A with diaeresis
143ÅLatin Capital Letter A with ring above
144ÉLatin Capital Letter E with acute
145æLatin Small Ligature AE
146ÆLatin Capital Ligature AE
147ôLatin Small Letter O with circumflex
148öLatin Small Letter O with diaeresis
149òLatin Small Letter O with grave
150ûLatin Small Letter U with circumflex
151ùLatin Small Letter U with grave
152ÿLatin Small Letter Y with diaeresis
153ÖLatin Capital Letter O with diaeresis
154ÜLatin Capital Letter U with diaeresis
155øLatin Small Letter O with stroke
156£Pound Sign
157ØLatin Capital Letter O with stroke
158×Multiplication Sign
159ƒLatin Small Letter F with hook
160áLatin Small Letter A with acute
161íLatin Small Letter I with acute
162óLatin Small Letter O with acute
163úLatin Small Letter U with acute
164ñLatin Small Letter N with tilde
165ÑLatin Capital Letter N with tilde
166ªFeminine Ordinal Indicator
167ºMasculine Ordinal Indicator
168¿Inverted Question Mark
169®Registered Sign
170¬Not Sign
171½Vulgar Fraction One Half
172¼Vulgar Fraction One Quarter
173¡Inverted Exclamation Mark
174«Left-Pointing Double Angle Quotation Mark
175»Right-Pointing Double Angle Quotation Mark
176Light Shade
177Medium Shade
178Dark Shade
179Box Drawings Light Vertical
180Box Drawings Light Vertical and Left
181Box Drawings Vertical Single and Left Double
182Box Drawings Vertical Double and Left Single
183Box Drawings Down Double and Left Single
184Box Drawings Down Single and Left Double
185Box Drawings Double Vertical and Left
186Box Drawings Double Vertical
187Box Drawings Double Down and Left
188Box Drawings Double Up and Left
189Box Drawings Up Double and Left Single
190Box Drawings Up Single and Left Double
191Box Drawings Light Down and Left
192Box Drawings Light Up and Right
193Box Drawings Light Up and Horizontal
194Box Drawings Light Down and Horizontal
195Box Drawings Light Vertical and Right
196Box Drawings Light Horizontal
197Box Drawings Light Vertical and Horizontal
198Box Drawings Vertical Single and Right Double
199Box Drawings Vertical Double and Right Single
200Box Drawings Double Up and Right
201Box Drawings Double Down and Right
202Box Drawings Double Up and Horizontal
203Box Drawings Double Down and Horizontal
204Box Drawings Double Vertical and Right
205Box Drawings Double Horizontal
206Box Drawings Double Vertical and Horizontal
207Box Drawings Up Single and Right Double
208Box Drawings Up Double and Right Single
209Box Drawings Down Single and Right Double
210Box Drawings Down Double and Right Single
211Box Drawings Up Double and Horizontal Single
212Box Drawings Up Single and Horizontal Double
213Box Drawings Down Single and Horizontal Double
214Box Drawings Down Double and Horizontal Single
215Box Drawings Vertical Double and Horizontal Single
216Box Drawings Vertical Single and Horizontal Double
217Box Drawings Light Up and Left
218Box Drawings Light Down and Right
219Full Block
220Lower Half Block
221Left Half Block
222Right Half Block
223Upper Half Block
224αGreek Small Letter Alpha
225ßLatin Small Letter Sharp S
226ΓGreek Capital Letter Gamma
227πGreek Small Letter Pi
228ΣGreek Capital Letter Sigma
229σGreek Small Letter Sigma
230µMicro Sign
231τGreek Small Letter Tau
232ΦGreek Capital Letter Phi
233ΘGreek Capital Letter Theta
234ΩGreek Capital Letter Omega
235δGreek Small Letter Delta
237φGreek Small Letter Phi
238εGreek Small Letter Epsilon
240Identical to
241±Plus-Minus Sign
242Greater Than or Equal To
243Less Than or Equal To
244Top Half Integral
245Bottom Half Integral
246÷Division Sign
247Almost Equal to
248°Degree Sign
250·Middle Dot
251Square Root
252Superscript Latin Small Letter N
253²Superscript Two
254Black Square
255No-Break Space
256Non-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.