ASCII art is any kind of artwork -- pictures, charts, cartoons, whatever -- drawn with the characters in the ASCII character set.
The ASCII (American Standard Code for Information Interchange) character set is a set of 128 characters (0 to 127) which are standard on almost all types of computer. The only characters used in ASCII art are those with the values 32 to 126, which are shown below, and 13, which represents a carriage return (new line). The other characters in the ASCII character set (0-12, 13-31, and 127) are control codes for representing things such as `end of file' and `backspace'; they should not be used in ASCII art.
032 [space] 048 0 064 @ 080 P 096 ` 112 p
033 ! 049 1 065 A 081 Q 097 a 113 q
034 " 050 2 066 B 082 R 098 b 114 r
035 # 051 3 067 C 083 S 099 c 115 s
036 $ 052 4 068 D 084 T 100 d 116 t
037 % 053 5 069 E 085 U 101 e 117 u
038 & 054 6 070 F 086 V 102 f 118 v
039 ' 055 7 071 G 087 W 103 g 119 w
040 ( 056 8 072 H 088 X 104 h 120 x
041 ) 057 9 073 I 089 Y 105 i 121 y
042 * 058 : 074 J 090 Z 106 j 122 z
043 + 059 ; 075 K 091 [ 107 k 123 {
044 , 060 < 076 L 092 \ 108 l 124 |
045 - 061 = 077 M 093 ] 109 m 125 }
046 . 062 > 078 N 094 ^ 110 n 126 ~
047 / 063 ? 079 O 095 _ 111 o
These characters are almost completely standard, except for a few slight variations which you should keep in mind when drawing and viewing ASCII art:
# (hash/pound):
a hash sign on most computers, a pound (£- currency)
sign on some British ones
| (bar):
a vertical line in most fonts, but in some it is split in the middle
^ (caret):
differs in size depending on the font used
~ (tilde):
appears in the middle of the line in some fonts, at the top in others
' (apostrophe/single quote):
tilts southwest-northeast in some fonts, is vertical in others
(this also applies to the comma ,).
Here's a small example of ASCII art using some of these variable characters: a snow-scene paperweight, drawn by Joan Stark. How good it looks will depend to some extent on which font and computer system you are using to view it.
____
.-" +' "-.
/.'.'A_'*`.\
|:.*'/\-\. ':|
|:.'.||"|.'*:|
\:~^~^~^~^:/
/`-....-'\
jgs / \
`-.,____,.-'
People use ASCII art for a variety of reasons, some of which are:
* it is the most universal computer art form in the world -- every computer system capable of displaying multi-line text can display ASCII art, without needing to have a graphics mode or support a particular graphics file format;
* an ASCII picture is also hundreds of times smaller in file size than its GIF or BMP equivalent, while still giving a good idea of what something looks like;
* it is easy to copy from one file to another;
* it's fun to do!
source:
http://www.geocities.com/SoHo/7373/faq.htm