or groups of coded symbols are observed to appear. 10 To illustrate the effectiveness of frequency analysis, let us perform a basic experiment. The following paragraph, which includes 1004 alphabetic characters, has been written without any preparation, or concern for contextual meaning (the reader may just skip it): During last winter, the weather has been unusually cold, with records in temperatures, rainfalls and snow levels throughout the country. According to national meteorology data, such extreme conditions have not been observed since at least two centuries. In some areas, the populations of entire towns and counties have been obliged to stay confined into their homes, being unable to take their cars even to the nearest train station, and in some case, to the nearest food and utility stores. The persistent ice formation and accumulation due to the strong winds caused power and telephone wires to break in many regions, particularly the mountain ones of more difficult road access. Such incidents could not be rapidly repaired, not only because these adverse conditions settled without showing any sign of improvement, but also because of the shortage of local intervention teams, which were generally overwhelmed by basic maintenance and security tasks, and in some case because of the lack of repair equipment or adequate training. The combined effects of fog, snow and icing hazards in airports have also caused a majority of them to shut down all domestic traffic without advanced notice. According to all expectations, the President declared the status of national emergency, involving the full mobilization of police and army forces. A rapid character count of the above paragraph (with a home computer11) provides the corresponding probability distribution. For comparison purposes, we shall use this time an English-language probability distribution based on a more recent (1982) survey. This survey was based on an analysis of newspapers and novels with a total sample of 100 362 alphabetic characters. The results are 