General Computer Science 320201 GenCS I & II Lecture ... - Kwarc

The first 32 characters are control characters for ASCII devices like printers
Motivated by punchcards: The character 0 (binary 000000) carries no information NUL,
(used as dividers)
Character 127 (binary 1111111) can be used for deleting (overwriting) last value
(cannot delete holes)
The ASCII code was standardized in 1963 and is still prevalent in computers today
(but seen as US-centric)
A Punchcard
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A punch card is a piece of stiff paper that contains digital information represented by the
presence or absence of holes in predefined positions.
Example 218 This punch card encoded the Fortran statement Z(1) = Y + W(1)
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The ASCII code as above has a variety of problems, for instance that the control characters are
mostly no longer in use, the code is lacking many characters of languages other than the English
language it was developed for, and finally, it only uses seven bits, where a byte (eight bits) is the
preferred unit in information technology. Therefore there have been a whole zoo of extensions,
which — due to the fact that there were so many of them — never quite solved the encoding
problem.
Problems with ASCII encoding
Problem: Many of the control characters are obsolete by now (e.g. NUL,BEL, or DEL)
Problem: Many European characters are not represented (e.g. è,ñ,ü,ß,. . . )
European ASCII Variants: Exchange less-used characters for national ones
Example 219 (German ASCII) remap e.g. [ ↦→ Ä, ] ↦→ Ü in German ASCII
(“Apple ][” comes out as “Apple ÜÄ”)
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