Ruby Programming/ASCII

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To us, a string such as "Hello world" looks like a series of letters with a space in the middle. To your computer, however, every String – in fact, everything – is a series of numbers.

ASCII

In our example, each character of the String "Hello world" is represented by a number between 0 and 127. For example, to the computer, the capital letter "H" is encoded as the number 72, whereas the space is encoded as the number 32. The ASCII standard, originally developed for sending telegraphs, specifies what number is used to represent each character.

On most Unix-like operating systems, you can view the entire chart of ASCII codes by typing "man ascii" at the shell prompt. Wikipedia's page on ASCII also lists the ASCII codes. Using an ASCII chart, we discover that our string "Hello world" gets converted into the following series of ASCII codes.

H  e   l   l   o   space  w   o   r   l   d
72 101 108 108 111 32     119 111 114 108 100

You can also determine the ASCII code of a character by using the ? operator in Ruby 1.8.

puts ?H 
puts ?e
puts ?l
puts ?l
puts ?o

The question-mark syntax no longer works in Ruby 1.9. Instead, use the ord method.

puts "H".ord
puts "e".ord
puts "l".ord
puts "l".ord
puts "o".ord

Notice that the output (below) of this program matches the ASCII codes for the "Hello" part of "Hello world".

$ hello-ascii.rb
72
101
108
108
111

To get the ASCII value for a space, we need to use its escape sequence. In fact, we can use any escape sequence with the ? operator.

puts ?\s
puts ?\t
puts ?\b
puts ?\a

As above in Ruby >= 1.9 use

puts "\s".ord
puts "\t".ord
puts "\b".ord
puts "\a".ord

instead.

The result:

Terminal emulators

You may not realize it, but so far, you've been running your Ruby programs inside of a program called a terminal emulator – such as the Microsoft Windows console, the Mac OS X Terminal application, a telnet client, rxvt, or X Window System programs such as xterm.

When your Ruby program prints out the letter "H", it sends the ASCII code for "H" (72) to the terminal emulator, which then draws an "H". When your Ruby program prints out a bell character, it sends a different ASCII code – ASCII code 7 – to the terminal emulator. In this case, the terminal emulator does not draw a symbol, but instead will typically beep or flash briefly. How each of the codes gets interpreted is largely determined by the ASCII standard.

Other character encodings

The ASCII standard is a type of character encoding. As mentioned above, ASCII only uses numbers 0 through 127 to define characters. There's a lot more characters than that in the world. Other character encoding systems – such as Latin-1, Shift_JIS, and the Unicode Transformation Format (UTF) – have been created to represent a wider variety of characters, including those found in languages such as Arabic, Hebrew, Chinese, and Japanese.

ASCII chart

Binary	Oct	Dec	Hex	Glyph
010 0000	040	32	20	?
010 0001	041	33	21	!
010 0010	042	34	22	"
010 0011	043	35	23	#
010 0100	044	36	24	$
010 0101	045	37	25	%
010 0110	046	38	26	&
010 0111	047	39	27	'
010 1000	050	40	28	(
010 1001	051	41	29	)
010 1010	052	42	2A	*
010 1011	053	43	2B	+
010 1100	054	44	2C	,
010 1101	055	45	2D	-
010 1110	056	46	2E	.
010 1111	057	47	2F	/
011 0000	060	48	30	0
011 0001	061	49	31	1
011 0010	062	50	32	2
011 0011	063	51	33	3
011 0100	064	52	34	4
011 0101	065	53	35	5
011 0110	066	54	36	6
011 0111	067	55	37	7
011 1000	070	56	38	8
011 1001	071	57	39	9
011 1010	072	58	3A	:
011 1011	073	59	3B	;
011 1100	074	60	3C	<
011 1101	075	61	3D	=
011 1110	076	62	3E	>
011 1111	077	63	3F	?

Binary	Oct	Dec	Hex	Glyph
100 0000	100	64	40	@
100 0001	101	65	41	A
100 0010	102	66	42	B
100 0011	103	67	43	C
100 0100	104	68	44	D
100 0101	105	69	45	E
100 0110	106	70	46	F
100 0111	107	71	47	G
100 1000	110	72	48	H
100 1001	111	73	49	I
100 1010	112	74	4A	J
100 1011	113	75	4B	K
100 1100	114	76	4C	L
100 1101	115	77	4D	M
100 1110	116	78	4E	N
100 1111	117	79	4F	O
101 0000	120	80	50	P
101 0001	121	81	51	Q
101 0010	122	82	52	R
101 0011	123	83	53	S
101 0100	124	84	54	T
101 0101	125	85	55	U
101 0110	126	86	56	V
101 0111	127	87	57	W
101 1000	130	88	58	X
101 1001	131	89	59	Y
101 1010	132	90	5A	Z
101 1011	133	91	5B	[
101 1100	134	92	5C	\
101 1101	135	93	5D	]
101 1110	136	94	5E	^
101 1111	137	95	5F	_

Binary	Oct	Dec	Hex	Glyph
110 0000	140	96	60	`
110 0001	141	97	61	a
110 0010	142	98	62	b
110 0011	143	99	63	c
110 0100	144	100	64	d
110 0101	145	101	65	e
110 0110	146	102	66	f
110 0111	147	103	67	g
110 1000	150	104	68	h
110 1001	151	105	69	i
110 1010	152	106	6A	j
110 1011	153	107	6B	k
110 1100	154	108	6C	l
110 1101	155	109	6D	m
110 1110	156	110	6E	n
110 1111	157	111	6F	o
111 0000	160	112	70	p
111 0001	161	113	71	q
111 0010	162	114	72	r
111 0011	163	115	73	s
111 0100	164	116	74	t
111 0101	165	117	75	u
111 0110	166	118	76	v
111 0111	167	119	77	w
111 1000	170	120	78	x
111 1001	171	121	79	y
111 1010	172	122	7A	z
111 1011	173	123	7B	{
111 1100	174	124	7C	\|
111 1101	175	125	7D	}
111 1110	176	126	7E	~