Glossary for Geospatial Science

  Technical vocabulary defined by MicroImages

book Glossary

ASCII:  American Standard Code for Information Interchange (pronounced “askee”).  The 7-bit (128 characters) used as a computer’s alphabet.  The Latin alphabet character set encoded into digital values between 0 and 127 includes lowercase and uppercase letters, the numerals 0–9, English punctuation marks, special symbols (such as @#$%^&*) and non-displaying characters often used as printer control codes.  The eighth bit, giving values from 128 to 255, is used in a nonstandard fashion and is not part of the standard ASCII code.  PCs normally have the “extended” character set in their system font for digital values from 128 to 255.  The characters used for values from 128 to 255 for TNTmips display screen fonts are unpredictable but can be displayed in the font style window.  Some fonts have no characters in this range while others have characters for some or all of these values.  ASCII is a proper subset of Latin-1, Unicode, and ISO 10646, which are the 1-byte, 2-byte, and 4-byte standards for international character encoding.

The term “ASCII file” is often used to mean a text-only file.  Documents in most word processors are not text-only files, since they include header information and formatting characters.  However most word processors have an export or print-to-file utility that will convert a document into a text-only ASCII format.