Catalan began to appear in written documents during the 12th century. It was standardized through the publication of spelling rules in 1913 and of a grammar in 1918. Standard literary incorporates features of several dialects but is largely based on the Central Catalan dialect as spoken by educated people in Barcelona.
The Catalan alphabet consists of the 26 letters of the basic Latin alphabet, the same 26 letters that make up the English alphabet. However, Catalan also makes frequent use of diacritics and the pronunciation of the letters, naturally, differs from English.
The following letter-diacritic combinations are used, but they do not constitute distinct letters in the alphabet: À, É, È, Í, Ï, Ó, Ò, Ú, Ü, and Ç.
K and W are used only in loanwords. Outside loanwords, the letters Q and Y appear only in the digraphs qu, qü and ny.
Catalan has 7 vowel phonemes. In addition, there are several diphthongs. There are 23 consonant sounds in Catalan.
Catalan is a pluricentric language with several codified standard pronunciation forms. The pronunciation of some of the letters is different in Eastern Catalan and Valencian. Apart from those variations, the pronunciation of most consonants is fairly straightforward and is similar to French, Occitan or Portuguese pronunciation.
The pronunciation of Catalan is not particularly vague, as long as you know all the rules. There are a lot of different pronunciation rules based on word stress and particular letter combinations, but they are not obscure or difficult to understand.