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## APPENDIXG 

## The ASCII Character Set 

ASCII (American Standard Code for Information Interchange) is the American variant of an officially-recognized, standard, international character set called the ISO (International Organization for Standardization) set. It specifies an encoding for 128 characters. Within the ISO character code there may exist national variants for 12 symbols (such as the currency symbol $). The 128 characters consist of95 which print as single graphics and 33 which are used for device control. The backspace control character is specifically used to allow overprinting of characters such as accents on letters in some languages. 

the 33 device-control characters: 

<img src='content_image/843327.jpg'>

