Mattel IntelliVision II 5872 Manuel d'utilisateur télécharger pdf (Page 211)

several years on early computer equipment. The ASR-33 was a mechanical

device (see [1402]EOU), so the only way to generate the character

codes from keystrokes was by some physical linkage. The design of the

ASR-33 assigned each character key a basic pattern that could be

modified by flipping bits if the SHIFT or the CTRL key was pressed. In

order to avoid making the thing even more of a kluge than it already

was, the design had to group characters that shared the same basic bit

pattern on one key.

Looking at the ASCII chart, we find:

high low bits

bits 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001

010 ! " # $ % & ' ( )

011 0 1 2 3 4 5 6 7 8 9

This is why the characters !"#$%&'() appear where they do on a

Teletype (thankfully, they didn't use shift-0 for space). The Teletype

Model 33 was actually designed before ASCII existed, and was

originally intended to use a code that contained these two rows:

low bits

high 0000 0010 0100 0110 1000 1010 1100 1110

bits 0001 0011 0101 0111 1001 1011 1101 1111

10 ) ! bel # $ % wru & * ( " : ? _ , .

11 0 1 2 3 4 5 6 7 8 9 ' ; / - esc del

1 2 ... 206 207 208 209 210 211 212 213 214 215 216 ... 238 239

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Mattel IntelliVision II 5872 Manuel d'utilisateur Page 211