Operation method

The "charsets.s7i" library contains definitions of various codepages. Codepages are represented as constant strings of length 256. Such a codepage string contains the Unicode representation of all charcters defined by the codepage. To convert the character 'Σ' from codpage 437 to UTF-32 the following needs to be done:

In codpage 437 the character 'Σ' is encoded with the number 228. The Unicode representation of 'Σ' is found at cp_437[229]. Note that 229 is used instead of 228 because the index of the first character in a string is 1 (cp_437[1] defines character 0 of codepage 437). The expression ord(cp_437[229]) is 931 (or 16#03A3) which is the Unicode representation of 'Σ'.

All Seed7 source files (*.sd7 and *.s7i) use UTF-8 encoding. Therefore the Unicode characters used in "charsets.s7i" are encoded with UTF-8 (an UTF-8 aware editor should be used to edit files containing UTF-8 characters). Although UTF-8 is used in the source files the codepage strings define the conversion to UTF-32 (the internal representation for chars and strings).