ASCII Code

Under Digital ElectronicsWe have discussed about the alphanumeric codes in a different article. We now know that these codes are used to represent different data, letters, numbers by distinguish symbols and characters, that’s why they are called alphanumeric codes. We also know that there are three types of alphanumeric codes, those are ASCII code, EBCDIC codes and Unicode, among which the first one is the most popular and used in maximum areas. And we will discuss about it in this article.

About the ASCII code

The name of the code ASCII stands for American Standard Code for Information Interchange and this is pronounced as ‘ask-ee’. They are used to represent alphanumeric data in computers, communication equipment in electronic device to represent the input and output in a more scientific manner. In 1967 this code was first published as a standard. From then it is constantly being updated and revised. In 1986 the latest version was called and published as ANSI X3.4. It is able to represent 2⁷ = 128 codes as it is a seven bit code. 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 there are 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.


Table ASCII code.

DEC	OCT	HEX	BIN	Symbol	HTML Number	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	0	Zero
49	61	31	110001	1	1	One
50	62	32	110010	2	2	Two
51	63	33	110011	3	3	Three
52	64	34	110100	4	4	Four
53	65	35	110101	5	5	Five
54	66	36	110110	6	6	Six
55	67	37	110111	7	7	Seven
56	70	38	111000	8	8	Eight
57	71	39	111001	9	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	A	Uppercase A
66	102	42	1000010	B	B	Uppercase B
67	103	43	1000011	C	C	Uppercase C
68	104	44	1000100	D	D	Uppercase D
69	105	45	1000101	E	E	Uppercase E
70	106	46	1000110	F	F	Uppercase F
71	107	47	1000111	G	G	Uppercase G
72	110	48	1001000	H	H	Uppercase H
73	111	49	1001001	I	I	Uppercase I
74	112	4A	1001010	J	J	Uppercase J
75	113	4B	1001011	K	K	Uppercase K
76	114	4C	1001100	L	L	Uppercase L
77	115	4D	1001101	M	M	Uppercase M
78	116	4E	1001110	N	N	Uppercase N
79	117	4F	1001111	O	O	Uppercase O
80	120	50	1010000	P	P	Uppercase P
81	121	51	1010001	Q	Q	Uppercase Q
82	122	52	1010010	R	R	Uppercase R
83	123	53	1010011	S	S	Uppercase S
84	124	54	1010100	T	T	Uppercase T
85	125	55	1010101	U	U	Uppercase U
86	126	56	1010110	V	V	Uppercase V
87	127	57	1010111	W	W	Uppercase W
88	130	58	1011000	X	X	Uppercase X
89	131	59	1011001	Y	Y	Uppercase Y
90	132	5A	1011010	Z	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	a	Lowercase a
98	142	62	1100010	b	b	Lowercase b
99	143	63	1100011	c	c	Lowercase c
100	144	64	1100100	d	d	Lowercase d
101	145	65	1100101	e	e	Lowercase e
102	146	66	1100110	f	f	Lowercase f
103	147	67	1100111	g	g	Lowercase g
104	150	68	1101000	h	h	Lowercase h
105	151	69	1101001	i	i	Lowercase i
106	152	6A	1101010	j	j	Lowercase j
107	153	6B	1101011	k	k	Lowercase k
108	154	6C	1101100	l	l	Lowercase l
109	155	6D	1101101	m	m	Lowercase m
110	156	6E	1101110	n	n	Lowercase n
111	157	6F	1101111	o	o	Lowercase o
112	160	70	1110000	p	p	Lowercase p
113	161	71	1110001	q	q	Lowercase q
114	162	72	1110010	r	r	Lowercase r
115	163	73	1110011	s	s	Lowercase s
116	164	74	1110100	t	t	Lowercase t
117	165	75	1110101	u	u	Lowercase u
118	166	76	1110110	v	v	Lowercase v
119	167	77	1110111	w	w	Lowercase w
120	170	78	1111000	x	x	Lowercase x
121	171	79	1111001	y	y	Lowercase y
122	172	7A	1111010	z	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