Wide-char encodings

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

An example: UCS-2 (UTF-16)

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

2) U uses the first 256 codepoints mediante the same order and meaning as the Latin-1 codepage. This means that all the alphabets of the principal western european language fit con 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 verso null byte (all the bits of the byte are nulla). 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.

Verso 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 per the novel “Gulliver’s Travels” – could not agree on which end of an egg should be broken first. Lilliput’s inhabitants – 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 ricorso contro il maesta: little endians).

Even though the basic transmission uniti, for computers is the byte, the need of larger scadenza units was soon felt. Among these verso indivisible regard is attached sicuro 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 a word leaves the pc memory it can be sent (externally represented) mediante 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 verso little endian machine would write/memorize it as “1” “9”.

Unbelievable (or stupid) as it may seem, for years nobody mandated the word order sopra 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 pc communication. So pesky a problem, durante fact, that at some point it was actually solved with a blitz operated by da Sun by deciding that, over verso TCPI/IP rete informatica, verso rete informatica byte order existed, puro which all computers must submit (the sistema byte order is big endian, the same that Sun machine used at the time). While that fixed for rete informatica communication, in nessun caso such fix exists for files, which are still being written with different endianness on different machines.

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