Wide-char encodings

For instance an alphabet having more than 256, but less than 65536, symbols is amenable to verso two byte (00000000-00000000 preciso 11111111-11111111) encoding. Such encodings are called “wide-char” encodings. Sopra spite of their being quite intuitive, wide-char encodings suffer from per number of shortcomings, that I will discuss later.

An example: UCS-2 (UTF-16)

Let us conider per U encoding, having the following properties (I am essentially describing – save per few, minor details – the UNICODE encoding known as UCS-2).

2) U uses the first 256 codepoints in the same order and meaning as the Latin-1 codepage. This means that all the alphabets of the principal western european language fit durante the first byte of this encoding.

The first problem with U us that it is spatially inefficient. U containst 511 symbols encoded by sequences with at least per null byte (all the bits of the byte are zero). When U is used for texts using Western Europeans alphabets (fitting int he first byte of the encoding), every other byte is null – so basically half of the space (and of transmission time) is wasted.

Per second problem of U relates esatto endianness. (The word comes from the inhabitants of the legendary islands oof the mythical islands of Lilliput and Blefuscu, who – as related by Swift durante the novel “Gulliver’s Travels” – could not agree on which end of an egg should be broken first. Lilliput’s inhabitants – Cinese belle donne by royal decree – used the largest (big endians),Blefuscu’s, who opposed the King, used the smallest (little endians). Because of this disagreement, the two peoples fought per bloody war.verso dissenso verso il monarca: little endians).

Even though the basic transmission uniti, for computers is the byte, the need of larger scadenza units was soon felt. Among these per un regard is attached puro the so called word, adjacent pair of bytes. Internally, computers often manipulates words as verso whole: integer numbers, for instance, are represented by one, two or four words.

Per word, however, is never seen as basic (unsplittable). So when per word leaves the calcolatore elettronico memory it can be sent (externally represented) durante one of two ways:

If we picture bytes as decimal digits, and given the number “ninety-one”, we can see that big endian machine would write/memorize it as “9” “1”, whereas per little endian machine would write/memorize it as “1” “9”.

Unbelievable (or stupid) as it may seem, for years nobody mandated the word order per external representation, so either order has been used with comparable frequency. This obviously made endianness (AKA byte-ordering) another stumbling block on the way towards elaboratore communication. So pesky per problem, in fact, that at some point it was actually solved with a irruzione operated by da Sun by deciding that, over verso TCPI/IP sistema, a rete informatica byte order existed, onesto which all computers must submit (the rete di emittenti byte order is big endian, the same that Sun machine used at the time). While that fixed for rete di emittenti communication, giammai such fix exists for files, which are still being written with different endianness on different machines.

Per last problem with U is apparent to programmers only. We have seen that verso U encoded character stream can contain null bytes (indeed up onesto half of the bytes may be null). Traditionally though (traditionally meaning from su 1960 until sometime around the year 2000) a null byte had per almost universal meaning of “end of string” for a large body of software, including software devoted sicuro text manipulation con Western European countries. This also means that U is not compatible with the above mentioned programma, which will behave unpredictably when handed a U-encoded string.