Types of writing systems The functions of writing Writing as a system of signs

Alphabetic systems
While cuneiform had many graphs that represented syllables, many syllables were not represented. The methods used for representing syllables that did not have distinctive graphs were quite unsystematic. The first writing system consistently based on the sound structure of a language was Linear B, a Mycenaean Greek orthography developed about 1400 BCE and deciphered in 1952 by Michael Ventris, an English architect and cryptographer. The script is strictly syllabic; each consonant-vowel pair is given a distinctive graph. As an example, a set of syllables that an alphabetic system would represent with the consonant p plus a vowel are all represented in Linear B by different graphs. Although the script is highly systematic, it provides a limited representation of the phonology of Mycenaean Greek. Greek contains many syllables that are not simple consonant-vowel combinations, and not all consonantal sounds are followed by vowels. Linear B is thus an incomplete script for representing the phonological structures of the spoken language. Hence, there are usually several ways of reading a series of Linear B graphs, and a correct reading depends upon the reader’s knowing what the text is about.
The final stage in the evolution of writing systems was the discovery of the alphabetic principle, the procedure of breaking the syllable into its constituent consonantal and vowel sounds. (See also alphabet.) According to the British linguist Geoffrey Sampson, “Most, and probably all, ‘alphabetic’ scripts derive from a single ancestor: the Semitic alphabet, created sometime in the 2nd millennium [BCE].” The Semitic script was invented by speakers of some Semitic language, possibly Phoenician, who lived in the northern part of the Fertile Crescent. Modern versions of Semitic script include the Hebrew script and the Arabic script. Their most prominent characteristic is that they have graphs for consonants but not for vowels.
The inventors of the Semitic orthography apparently took the acrophonic principle, that of representing sounds by pictures of things whose names begin with that sound, from Egyptian hieroglyphic, a form of writing not different in principle from Akkadian cuneiform. The hieroglyphic sign  , depicting waves of water, represented the sound /n/, the first sound of the spoken word for water. By means of this principle a 22-graph system was constructed with a memorized order, beginning alef, bet, gimel, that was suitable for representing a full range of meanings. These graphs represented the consonants of the language, vowels remaining unrepresented. This fact has led some scholars, notably Gelb and Havelock, to claim that Semitic scripts are not true alphabets but rather unvocalized syllabaries. Other scholars, noting that the graphs represent consonants rather than syllables—for example, pa, pe, pi, po, and pu would all be represented by the same character—insist that the script is an alphabet. The controversy is circumvented by referring to Semitic scripts, following Sampson, as consonantal writing systems. While such a script would be greatly limited in explicitness or completeness for a language with complex syllable structure such as English, it is relatively complete for Semitic languages in which vowel differences are rarely contrastive.
To illustrate, the following oral forms have in common the three consonantal phonemes /k/, /t/, and /b/ with different vowel sounds interdigitated. The meanings all contain the root meaning “write,” and the vowel differences mark subject, tense, and aspect: katab ‘he wrote,’ katabi ‘I wrote,’ katebu ‘they wrote,’ ketob ‘write,’ koteb ‘writing,’ katub ‘being written.’ All are written simply ktb.
Because vowel sounds generally distinguish grammatical rather than lexical meaning, some Semitic writing systems never developed any device for representing them. This is not necessarily a flaw in the orthography.