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:  ACK  Acknowledge  FF  Form Feed  BEL  Bell  FS  File Separator  BS  Backspace  GS  Group Separator  CAN  Cancel  HT  Horizontal Tab  CR  Carriage Return  LF  Line Feed  DCl  Device Control 1  NAK  Negative Acknowledge  DC2  Device Control 2  NUL  Null  DC3  Device Control 3  RS  Record Separator  DC4  Device Control 4  S1  Shift In  DEL  Delete  SO  Shift Out  DLE  Data Link Escape  SOH  Start of Heading  EM  End of Medium  STX  Start of Text  ENQ  Enquiry  SUB  Substitute  EOT  End of Transmission  SYN  Synchronous Idle  ESC  Escape  US  Unit Separator  ETB  End of Transmission Block  VT  Vertical Tab  ETX  End of Text  247 