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17 lines
824 B
Markdown
17 lines
824 B
Markdown
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title: Strings for ACM ICPC
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---
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## Character Codes
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Character codes are mappings between numbers and symbols which make up a particular alphabet.
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The *American Standard Code for Information Interchange* (ASCII) is a single-byte character code where $2^7 = 128$ characters are specified.
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Symbol assignments were not done at random. Several interesting properties of the design make programming tasks easier:
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- All non-printable characters have either the first three bits as zero or all seven lowest bits as one. This makes it easy to eliminate them before displaying junk.
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- Both the upper and lower case letters and the numerical digits appear sequentially
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- We can get the numeric order of a letter by subtracting the first letter
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- We can convert a character from uppercase to lowercase by $Letter - "A" + "a"$
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