February 9, 2009

Because You ASCIId Part I

Filed under: Main — admin @ 12:01 am

Back in the dawn of the computer age, there existed a thing called ASCII, one of many common and confusing computer acronyms. ASCII stands for American Standard Code for Information Interchange, but more importantly it’s pronounced ASK-ee. That was about all you needed to know in the old days.

Things were hell back in the computer world of the 1970s. Each different computer was its own system, unable to share information with different computers. That made exchanging information difficult, if not impossible. Then along came ASCII.

ASCII is simply a code. It’s used in computers to assign common characters to numbers, like the old Secret Decoder Rings from days gone by. That’s because computers deal with numbers. They don’t know characters. So by adopting the ASCII standard, computers could share information and have that information be the same on every ASCII-based system. That’s the Information Interchange, the II part of ASCII.

The ASCII codes are defined as 0 through 127, which is how many values (128, actually) you can pull out of a 7-bit byte. Yep, not all computers used the 8-bit byte back in the 1970s.

Codes 0 through 31 were defined as control codes. They did various screen and printer commands, and also provided a way to organize data. They’re called control codes because the character they represent is produced by pressing the Ctrl (control) key on the keyboard. Here they are:

Code Character Code Character Code Character Code Character
0 ^@ 8 ^H 16 ^P 24 ^X
1 ^A 9 ^I 17 ^Q 25 ^Y
2 ^B 10 ^J 18 ^R 26 ^Z
3 ^C 11 ^K 19 ^S 27 ^[
4 ^D 12 ^L 20 ^T 28 ^\
5 ^E 13 ^M 21 ^U 29 ^]
6 ^F 14 ^N 22 ^V 30 ^^
7 ^G 15 ^O 23 ^W 31 ^_

While the table above may look pretty, some of the codes are known to you: ^H is Backspace, ^I is the Tab, ^M is the Carriage Return, ^[ is the Escape (Esc key). While it’s not really used for anything, it’s important to know that the ^^ code is pronounced “Control-Control.”

Codes 32 through 126 are all common keyboard characters and symbols. They’re divided up into three groups:

Codes 32 through 63 are punctuation symbols and numbers:

Code Character Code Character Code Character Code Character
32 space 40 ( 48 0 56 8
33 ! 41 ) 49 1 57 9
34 42 * 50 2 58 :
35 # 43 + 51 3 59 ;
36 $ 44 , 52 4 60 <
37 % 45 53 5 61 =
38 & 46 . 54 6 62 >
39 47 / 55 7 63 ?

Codes 64 through 95 represent lower case letters, plus a few more symbols:

Code Character Code Character Code Character Code Character
64 @ 72 H 80 P 88 X
65 A 73 I 81 Q 89 Y
66 B 74 J 82 R 90 Z
67 C 75 K 83 S 91 [
68 D 76 L 84 T 92 \
69 E 77 M 85 U 93 ]
70 F 78 N 86 V 94 ^
71 G 79 O 87 W 95 _

Codes 96 though 126 represent upper case letters, plus even more symbols:

Code Character Code Character Code Character Code Character
96 ` 104 h 112 p 120 x
97 a 105 i 113 q 121 y
98 b 106 j 114 r 122 z
99 c 107 k 115 s 123 {
100 d 108 l 116 t 124 |
101 e 109 m 117 u 125 }
102 f 110 n 118 v 126 ~
103 g 111 o 119 w    

Finally, code 127 represents the Delete character.

And that’s ASCII.

Yes, that’s it.

What? You think there are 256 ASCII codes? Well, you’re probably an old-timer like me! And you remember the early days of the PC when there were 256 ASCII codes. But, just as I was, you’re wrong. Next post I’ll explain why.

No Comments

No comments yet.

RSS feed for comments on this post.

Sorry, the comment form is closed at this time.


Powered by WordPress