What is ASCII?

What is ASCII?

Usually when the term ASCII is used, it is to refer to a text document. If a file is described as “ASCII text”, this means you can view the contents of the file, change it with an editor, or print it with a printer. It does not contain any special embedded control characters. “ASCII” is an acronym that stands for American National Standard Code for Information Interchange. It is a widely used standard for encoding text documents on computers.

As part of this system, every letter, number, and punctuation symbol has a corresponding number, or “ASCII code”. For example, the character for the number 1 has the code 49, capital letter A has the code 65, and a blank space has the code 32. This encoding system not only lets a computer store a document as a series of numbers, but also lets it share such documents with other computers that use the ASCII system.

Documentation files or program source code files are usually stored as ASCII text. In contrast, “binary” files, such as executable programs or graphical images, contain other characters that cannot be normally displayed or printed, and are usually illegible to human beings.

The format of a file, whether ASCII or binary, becomes an issue when you are transferring files between computers. For example, when using FTP, ASCII text files may be transferred without any special consideration. To exchange binary files, however, you must enter the command “set binary” in many FTP clients to instruct the computer to correctly transmit the special characters in the file. See the references below for more information about how to correctly transfer files.

A table of ASCII character codes.

Note: Dec refers to the decimal number of a character (Char) and Hex refers to its hexadecimal equivalent.

Dec	Hex	Char		Dec	Hex	Char		Dec	Hex	Char		Dec	Hex	Char
0	00	NUL		32	20			64	40	@		96	60	`
1	01	SOH		33	21	!		65	41	A		97	61	a
2	02	STX		34	22	“		66	42	B		98	62	b
3	03	ETX		35	23	#		67	43	C		99	63	c
4	04	EOT		36	24	$		68	44	D		100	64	d
5	05	ENQ		37	25	%		69	45	E		101	65	e
6	06	ACK		38	26	&		70	46	F		102	66	f
7	07	BEL		39	27	‘		71	47	G		103	67	g
8	08	BS		40	28	(		72	48	H		104	68	h
9	09	TAB		41	29	)		73	49	I		105	69	i
10	0A	LF		42	2A	*		74	4A	J		106	6A	j
11	0B	VT		43	2B	+		75	4B	K		107	6B	k
12	0C	FF		44	2C	,		76	4C	L		108	6C	l
13	0D	CR		45	2D	–		77	4D	M		109	6D	m
14	0E	SO		46	2E	.		78	4E	N		110	6E	n
15	0F	SI		47	2F	/		79	4F	O		111	6F	o
16	10	DLE		48	30	0		80	50	P		112	70	p
17	11	DC1		49	31	1		81	51	Q		113	71	q
18	12	DC2		50	32	2		82	52	R		114	72	r
19	13	DC3		51	33	3		83	53	S		115	73	s
20	14	DC4		52	34	4		84	54	T		116	74	t
21	15	NAK		53	35	5		85	55	U		117	75	u
22	16	SYN		54	36	6		86	56	V		118	76	v
23	17	ETB		55	37	7		87	57	W		119	77	w
24	18	CAN		56	38	8		88	58	X		120	78	x
25	19	EM		57	39	9		89	59	Y		121	79	y
26	1A	SUB		58	3A	:		90	5A	Z		122	7A	z
27	1B	ESC		59	3B	;		91	5B	[		123	7B	{
28	1C	FS		60	3C			94	5E	^		126	7E	~
31	1F	US		63	3F	?		95	5F	_		127	7F	DEL