Letter frequency xz. Modern International Morse code (generally believed to have been developed by Alfred Vail based on English-language letter frequencies of the 1830s) encodes the most frequent letters with the shortest symbols; arranging the Morse alphabet into groups of letters that require equal amounts of time to transmit, and then sorting these groups in increasing order, yields e it san hurdm wgvlfbk opxcz jyq. Similar ideas are used in modern data-compression techniques such as Huffman coding. Letter frequency was used by other telegraph systems, such as the Murray Code. Letter frequencies, like word frequencies, tend to vary, both by writer and
History of the Arabic alphabet a dot below = "i", a dot on the line = "u", and doubled dots giving "tanwin". However, this was cumbersome and easily confusable with the letter-distinguishing dots, so about 100 years later, the modern system was adopted. The system was finalized around 786 by al-Farahidi. Before the historical decree by Hajjaj ibn Yusuf, all administrative texts were recorded by Persian scribes in Middle Persian language using Pahlavi script, but many of the initial orthographic alterations to the Arabic alphabet might have been proposed and implemented by the same scribes. When new signs were added to the Arabic alphabet, they